I posted this problem in the wrong section orrigionally (cooling) I think for this is a wiring problem.
1 second after a cold start the cooling fan turns on. I have replaced all sensors, Wiring harness from the ECM to the sensors under the hood, Fan relay, and swapped out my ECM to another that before would not engage the fan below 230 degrees. I tried disconecting all the sensors and the fan still engages right away. I have also upgraded to a serp set up. I have removed all the A/C stuff and I am running an A/C delete box. All the wires that attached to the A/C I have tucked inside the inner fender and covered the end so as not to short out. I think the problem resides on the inside of the car. Is there a relay for the A/C and where is it. I was informed that this is the default for the fan to run while the A/C is on even if the car is cold. I have the single cooling fan. Any help would be greatly appreciated.

 

No one has any ideas of where to look? I would think that there would be at least one wiring Guru on here. I am not able to find the wiring diagram for an 85 TA with TPI and the 86 wiring harness has different colored wires in it. The only wiring scematic I have found is for an 85 TBI which is also different. I am extreemly frustrated for I have no other ideas save to replace yet another harness and hope it helps. Finding another in the junk yards is a little difficult for it must be an 85 W/TPI...a rare bird indeed. Is there a wire that links the A/C to the ECM to turn on the fan? If so what color is the wire and can I install a toggle switch there to controll the fan?

 

Had a similar problem with my 91 V6 converted to V8. My problem went away by itself after about a dozen starts. Check the fan relay. Sould be two large wires, power in (always hot) and power out(when relay engaged) to fan and two smaller wires, brown with white stripe supplies 12 volts with key on from the fan fuse under the dash and a green with white strip from the ECM that provides the ground. Must be your ECM is providing the ground before engine reaches temperature. Do you have a bad sensor telling the ECM to provide the relay with a ground thereby activating the fan?

 

Replaced all wires under the hood from the ECM to the sensors (includes the Fan Relay) have replaced all the sensors they are all new. I can disconect the green white wire and the fan still comes on. I checked to see if it was grounded and it is not other wise the fan would come on when the ignition is turned on...the fan will not come on untill the car starts. Something is telling the ECM to turn on the fan and I don't think it is from under the hood for everything is new. The only thing under the hood that should trigger the fan is the green and white wire (passenger head)and the Yellow and black from the Temp sensor on the intake. Is there anything else I missed? Tried new fan relay (passenger side front by radiator for Trans Am)and same symptoms.
This has been going on now for about 2 mnts and is my daily driver.

 

1) Patience, my friend.

2) What ECM are we talking about? TPI?


3) This is contradictive. If you disconnect the ECM from the relay (the green/white wire), the ECM cannot command the relay anymore.
So whatever is turning the fan on is not the ECM.

Actually, where did you disconnect the green/white wire?
a) If at the relay, that would point to faulty fan wiring.
b) If by the ECM, I'd guess somebody must have added a splice to the green/white relay and either ground it or put it on a hidden switch. This happens a lot here, don't be surprised.

Ad a) Also a possibility of a hack job by the previous owner. I remember both my fans were wired DIRECTLY to the ignition fuse in my fuse box when I bought my car. As I said, previous owners do shitty things to these cars. Don't let that catch you off guard.

Hope this helps.
Lou

 

Okay the car is an 85 Trans Am with TPI. I have replaced the wiring harness from the ECM inside the car (under the passenger side of dash) for the one I had was hacked and I was having problems with it...the clear harness end was burned from the MAF (large brown wire) and all the black and white ground wires were all soldered together and some had come loose...I had to giggle the wires sometimes to engage the fuel pump when it would not engage...then I had this new problem with the fan running all the time so I found (luckly) a complete unmolested harness from a car in the junk yard. No motor and all the wires were labeled. After replacing this harness the fan still runs but only at start up (same problem with the old harness). I disconected the green/white wire from the passenger side of the head. If I ground it the fan will run as soon as I turn the ignition to the on possition, hence rulling out a ground fault in the green/white wire for the fan will only turn on after the car starts. I also replaced the ECM and the prom chips with one that did not even run the cooling fan before. Before all this the fan would run once the temp hit around 160 degrees (Hypertech chip) now using the Supper chip. There has to be something else commanding the ECM to turn on the fan other than the temp sensor. I just do not know what would. I will be disconecting the A/C head inside the car next to see if it makes a difference.

 

Good info, good troubleshooting. Kudos.

Let me sum up what we know. If I'm wrong somewhere, please correct me, I might make an assumption or two.
- the relay circuit for the fan works fine, correctly commanded by the green/white wire
- the fan does NOT come on with ignition but it comes on once the engine is turning

Now I'm not clear at all about the ECM exchange. Did the other ECM change the behavior? Did it work better or worse before?

You can perform the ultimate test and (if you can) pull the green/white wire and pin from the ECM connector (pin E8 on C3). If the cooling fan still comes on, the ECM is out of the game here.

Hope this helps.
Lou

 

I switched ECM's just to rule that out of the equasion...it helps to have spare parts... Yes the fan will still come on if I remove the green white wire from the ECM...Disconecting it from the relay still resulted with the fan comming on. It was easier to remove the pin from the relay than removing the pin from the ECM conector. Something is telling the fan to come on the wires for the fan run through the relay and there is another wire by the battery where the ECM fuse is. If pulled will not run the fan but the car wont start either and jumping the ALDL port will not run the fan either when this fuse is pulled.

 

Alright, you just answered your own question from earlier.
If you remove the green/white wire from the relay and yet the fan still comes on, something is sending power to the fan while bypassing the relay.

The easiest way to find that extra power supply would be to trace the fan wire from the fan backwards.

Have you tried pulling the fan relay? If you do, does the fan still come on? That rules out the ECM, A/C or even the temp switch in the passenger head.

Hope this helps.
Lou

 

No the fan will not come on if I disconect the relay, neither will the car start...I think it has something to do with the tan/white wire for it will not start with this single wire pulled (...but the fan will still run). It has been really cold here so I have been driving around with the fan fuse pulled from the inside fuse box.

 

That sounds like the Fuel Pump relay for a change.
That one ALSO uses a green/white wire. Watch out, that wire supplies powre to the relay, though. Don't ground it.

Lou

 

Ah that reminds me I had a check engine light come on (before swapping out the harness) code 54 It was one of those days that I had to giggle wires before the fuel pump would prime and right after the car started the check engine light came on and this is what it stated. I have not tackeled this problem yet could it be related to my fan problem?

Code 54 ~ Using digital Ohm meter, check fuel pump circuits for shorts or opens.

 

Keep in mind that pulling the fan fuse may also affect your alterantor. At least on my car the brown/white wire for the fan relay is also connected to the alternator. Without the 12 volt signal to the alterantor, I fried the internal regulator.

 

Good to know. I have not been able to do any more trouble shooting. When I converted to the serp set up I needed the correct plug for the new alternator. The only one I could find stated it was for a voltage regulator, this plug has 3 wires a red a black and a brown. I cliped off the brown for I figured this one would not be needed and it is not used on the cars with the serp set up (2 wire system). Perhapes this is where it is getting the juice. I also remember when doing the wiring that there was another wire hooked up (inline) to the green white wire (I need to find out where it goes). I also back tracked the wires from the fan And the black wire goes directly to ground, beside the relay. The possitive wire coming out of the relay goes directly to the fan. Knowing this there are only 2 wires that can be actuating the fan, the green and white or the tan and white. I just need to see which one is becoming a ground after the car starts to activate the relay...this will help to narrow down where the problem is coming from. I will post up my findings Tomorrow.

 

There are only two possibilities-I'm assuming single fan setup?:

1) The green-white fan relay control ground wire (connected to the temp switch in cylinder head) is being grounded somewhere else after the engine starts. This sensor wire is also ground thru an A/C pressure switch-thru the ecm (you say the a/c wiring is tucked away somewhere?) on some earlier models it's grounded at the A/C control head. Any one of these sources can ground the wire and engage the relay. With the engine and fan running pull the lead off the switch and test its continuity to ground. Test the continuity of the switch to ground. If the lead is grounded it may be worthwhile to run a new lead from the relay as you no longer need the a/c fan operation. If the switch is grounding it may be failing and closing, which would be unusual failure but, I guess, possible.

2) The fan is receiving power from somewhere other than the relay. Easy enough to check. Does the fan run with the relay unplugged? Continuity between the fan power wire and the plug on the relay? Even if it shows continuity, some other power source could be spliced into it. The 'hot in run' control source should be a brown wire (though my diagrams may be wrong). It should also be tapped into the alternator. The relay should, however, not pass this power along to the fan-you've replaced the relay already.

Heavier gage power wire to fan should be red/black. The always hot power source to the relay should be same heavier gage orange wire. This source may come from a lug at the starter. Disabling the heavy wire at the battery would cut power to other systems as well. It can be easy to mix up the fuel pump relay and the fan relay. Continuity check between the fan/relay or switch relay to make sure you've got the right one.

 

Thank you for the information I have some more work to do. Here is what I have found.

1 large orange +: runs direct from battery (fusible link) to relay. does not branch out to any other system.

1 black at relay +: turns to Red direct from relay to fan.

2 green/white : 1 direct from head to relay /1 direct from relay to ECM (PCM)

1 tan/white goes from relay direct to inside harness (gray conector) becomes dark brown wire (there are 2 large pink and black here as well).

according to the wiring scematic this brown should run direct from FAN fuse to the relay. If I disconect this wire the fan will not run at all.

Found why the fan was not working for the previous owner of the doner harness. Found relay# R9902CHK which is a 4 pin but the last pin is in the wrong location (blank). The car will start and the fan will not run at all if the large orange is not conected the correct relay looks like this --- - and this relay (wrong one) looks like this ---- obviously looking down where it connects. I need to find which wire is triggering the ECM. I can disconect the Green and white and the fan will still run. This only leaves the brown which I cannot disconect or no fan at all. I am thinking of just running a toggle swith off of this brown wire. I am unnable to see how the alternator has anything to do with the wiring of the fan. The only scenerio that I can see would be if the fusable link blew at the battery and someone re-attached to the positive linked to the alternator.

 

The green/white wire should be the control lead. Grounding this lead should engage the relay and allow it to pass power. You have two connected at the relay? Are you disconnecting both and the fan still runs?

The tan/white/brown wire should be your "hot in run" +12v control voltage source. This wire provides the voltage necessary to close the relay when the green/white wire is grounded. This voltage does NOT pass to the fan.

Sounds like your relay is closing without the control lead grounded. Try removing the relay from the mount, isolate it, and see how it behaves. Test the relay for proper function: connect a +12v source to the lead where the tan/white/brown wire connects, ground the lead where the green/white wire connects and check for continuity across the other two terminals (where the orange and black larger gage wires attach. Voltage should only pass when the control lead terminal is grounded.

 

Okay, I will be re-testing this harness (and write everything down) The other tests were performed on the old harness but this one is behaving the same way (in terms of the fan) If I snip the wire from the (ECM) side of the relay the fan will not turn on...I now remember this (I will need to re-check) because I tried just having the green/white connected from the temp switch (passenger side head) to the relay and it would not turn it on even after the temp rose over 230 degrees (I will re-test this as well)

 

I remember now that if I disconect the green/white from the ECM then the fan will not turn on (jumping the ALDL A,B) and it will not run when I start the car. There must be a wire feeding the ECM and telling it to turn on the fan other than the temp switch for I have replaced the sending temp switch located on the top of the intake and the fan still runs after the car starts. The only other wire that should feed the ECM would be from the A/C...just need to find this wire.

 

[(you say the a/c wiring is tucked away somewhere?) on some earlier models it's grounded at the A/C control head. Any one of these sources can ground the wire and engage the relay. With the engine and fan running pull the lead off the switch and test its continuity to ground.

Please let me know which wire you are referring to.

 

You said 'top of the intake', the CTS for the ECM is mounted there. The temp switch for the fan is mounted between #6 and #8 on the pass side cylinder head. Single wire-grounds thru the switch to the cylinder head when set point is reached. Has a plug similar to the KS mounted below in the block. The ECM does NOT use the temp reading from the CTS for engaging the fan.

Your A/C wiring should have had a plug to a pressure switch at the filter/dryer that also engaged the fan thru the ecm. Best of my knowledge (and per the wiring diagram) your model should not have been run thru the control head.

 

Well what the heck...I am lost. I spent Hours last night trouble shooting and this is what I found (wrote everything down after every step). I will try and make this a simple as possible...ya right!!! I apoligize for this long post and thank you guys for the help!!!

Fan will run when car is started when all these are removed:
Radio, A/C head unit (inside of car), Alternator (removed all wires and seperated each one) Coolant fan temp switch (pass head).

Car will start but no fan when Relay is removed.

Fan will not run if these are disconected:
Fan relay, Fan fuse, green/white wire going from Relay to ECM.

Relay test:

removed relay from vehicle, using jumper wires connected the Orange (direct from battery+) to the tan/white (becomes brown inside of car) and the doors locked and when I removed the wire the doors unlocked. I am guessing this happened for I was running voltage backwards through the system...just a guess.

Re-installed relay to test green/white:

Using a CONDUCT TITE (R) combination voltage continuity tester.
touching the leads to the battery read continuity and 6v 12v dc (it is working properly)

hooked tester to + (ECM green/white) - (RELAY green/white)
ignition off (continuity only)
ignition on (neutral no lights)
started car (continuity only while cranking) car starts reads 6V 12V no continuity. No Fan

WHILE USING THE TESTER THE FAN WILL NOT RUN!
re-conected the wire back to itself and the fan will run once started.

attached green/white from relay to ground- fan runs with ignition on

Testing ECM:
attached green/white from the ECM side to the tester and then to ground.
no lights. started car 1 second after the car started the continuity light came on showing continuity to ground...no voltage.

 

Have you disconnected the green/white wire from the ECM (connector C3, pin E8). That's the only way to put the blame either on the ECM or the wiring.

Lou

 

How do I remove this pin from the ECM plug harness? I snipped the wire under the hood that feeds the ECM. I can guarantee that if I snip the wire at the ECM It will yield the same results for there is nothing else conected to this wire. The green/white runs directly from the ECM to the Relay (feed) then there is a second wire that runs from the relay (same conector in relay harness) that the temp switch feeds this wire was disconected from the head during the tests. There is something telling the ECM to engage the cooling fan which it is doing. I have replaced the harness and the ECM and still have the exact same senerio. Cooling fan runs right after car starts. What information does the ECM gather to turn on the fan? I figured it would come from the temp sensor and the A/C. I do not want to just start hacking wires for everywire that gets cut is another potential for a problem. You guys (BIG BABY LOU and NAF) certinally know more than I do and I will follow what ever instruction you give for this is driving me INSANE!

 

Sounds like your ecm is grounding the control lead and engaging the fan. Could be that the A/C pressure switch wire is grounded, or closed/open (I'm not sure of the normal nature of this switch) somewhere tucked away and sending this false 'AC on" signal to the ECM.

Why not: Disconnect the ECM from the relay and allow only the temp switch in the pass side head to control the fan. You've done away with the A/C anyway. There's no other purpose for the ECM to be connected and it won't know it's not. Or dig in the harness for the A/C pressure switch connector, short it/open it and see how the ECM signal to the relay behaves.

Everything else you did seemed normal except that part about engaging the door locks? That was weird and don't do it again.

After I posted, saw your reply: "What information does the ECM gather to turn on the fan?" The only function the ECM has in fan operation (single fan) is to convert the signal it receives from the AC and ground the relay lead.

 

Thank you I have a way to go now....however I would like to find this wire from the A/C would it be on the passenger side or the drivers side? Also I remember reading on here somewhere that the temp switch will not engage it untill it reaches like 240 degrees. And why would a different chip make any difference on when the fan engages if the ECM does not look at this information. I have one ECM that would engage the cooling fan at 130 degrees and the other ECM would not engage the fan at all (did not try running over 230 degrees) Also there is another wire that Controlls the fan and that is the ALDL port a,b but this is with ignition on. I read in the sticky on the top of the page about installing a different temp switch on the head to
have the fan engage sooner as well....I did not finish reading for this was not my problem to begin with. I sincerly do apreciate all the help you have given me so far.

 

I've got one wiring diagram that shows the A/C pressure switch is normally grounded. If this is true, disconnecting it may send the 'AC ON' signal to the ECM. The wiring diagram linked from the tech pages on this site:

http://www.geocities.com/vtcamaro/Pi...rams/pg172.jpg

Shows it normally open. Neither shows the temp switch in the head. Another reason I hate to attempt to draw a definitive conclusion from a wiring diagram.

Both do, however, show the lead from the A/C switch to the ECM as being dark green. The ECM pin number in the diagram linked above should be right. If you wanted to get crazy, you could pull the connector off the ECM and test that lead-see if it is grounded or open; reconnect it and reverse it's mood. See if it changes the fan behavior. You may have to cut it but you can solder it back later WITH shrink wrap. That would tell you that it's definitively between the A/C switch and the ECM.

That's what I might do if I was feeling frisky, but it IS getting cold outside.
----------
If the car is equipped with heavy duty cooling system (dual fans) the ECM controls operation of the second fan. Thought it was only available with the 5.7 but there's an 85 wiring diagram with it shown. Go figure. 'Course it could be an error in the diagram.

A lower temp fan switch is available. A search will turn up the part number for a buick gn (I think) stock type that has a much lower set point. Cheaper than an aftermarket replacement.

 

If you want to assume that it's the ECM controlling the fan relay, we could do that. Hopefully you're right.

The ECM controls the fan based on at least two inputs: the coolant temperature and the A/C fan pressure switch. I believe (but don't quote me on it) that the A/C fan pressure switch would make the fan turn on even if the engine isn't running (but I could be wrong ).

It should be safe to assume that if you disconnect the switch and the fan still turns on, it's not the switch. It is located on the passenger side, down below on the subframe, on the A/C line, next to the engine exhaust manifold. You guessed it, it will have a green and black/white wires.

Another possibility is that your CTS (Coolant Temperature Sensor) is bad and telling the ECM that the engine is hot. The ECM then turns on the fan as soon as the engine starts. It's a likely scenario. You can disconnect the CTS (on the front of the intake manifold) and measure the resistance on the sensor pins. If the resistance is below let's say 150 ohms even with the engine cold, the CTS is bad and being source of your problem.

Another option is that the ECM calibration module just commands it to turn the fan as soon as the engine starts. However, that's not standard stock behavior so if you tested stock chips, this would rule it out.

Lou

 

I will test this theory with the CTS. If the wire for the A/C needed ground then everyone who ever removed their A/C would have experienced the fan running at all times (and would be common knowledge). I have not "tested the CTS" like this I used another one I had laying around and rested it on the top of the intake and swapped wires. Could be a chance that this could be the problem. I will run some more tests and post when I find some diffinitive information.

 

An aftermarket chip could always be programmed to command fan operation based on CTS readings. I can't say definitively that the stock chip does NOT command fan operation based on CTS. I have read otherwise though.

Disconnecting the CTS at the water neck would open the circuit and make the ecm think the motor is cold but you've got to ensure there are no shorts in the leads going to the CTS. Shorting the two leads would tell the ECM that the motor is full hot. You can test the leads for continuity between them.

I agree that it's unlikely for the pressure switch to command fan operation simply by being unplugged. Just noted the diff in the diagrams.

 

Well I have continuity at all times at the CTS on the intake checked by disconecting the Weather Pack at the sensor and jumping the tester accross the female terminals. Checked with the ignition on, off, and running. No voltage only continuity. I did not use a volt meter just the combination continuity voltage tester.

 

You're reading continuity between the two wires going to the CTS?

Could be as simple as replacing the two wire pigtail connector at the CTS. They can get abused and a lot of replacement CTS sensors come with replacement pigtails. A replacement pigtail is also available separately at AZ of one of the others, usually hanging in their electrical parts aisle. You may want to clip the connector loose and see if the two leads are still shorted together. That way you'll know if it's at the connector or deeper in the wiring.

The ECM sends a voltage signal to the CTS, which is a variable resistor. Higher temps=less resistance. If the wires are shorted together there is essentially no resistance between them and the ECM interprets this as full hot. Some ECMs are programmed to send a trouble code though when they see this high of a reading and set the check engine light. Don't know for sure on yours or not.

 

I have gotten the check engine light on before when I had a short there (but the fan was not running all the time), The pig tail is new, like 2 mnts old. I will use my volt meter and check and see what it does and see if maybe the problem is in the weater pack or in the wiring itself. I did transfer over the "new" pig tail from the old harness for the weather pack was broken...go figure.

 

Well I checked all the wires and could not find anything shorting out. I did find only 6 volts running through the wire that originaly ran to the A/C high pressure line. I tried grounding this wire and the one next to it and still had the same problem. I am not finished with this but I have taken it as far as I can and I refuse to cut up this harness for I believe the problem resides elsewhere. I will take it to a specialist sometime within the next few mnts. In the mean time I installed a toggle switch. I did it the way listed below for after this problem has been resolved all I will need to do to is remove the male conectors I installed in place of the fuse and re-install the fuse. This bypasses everything and controlls the fan soley via a switch.

1) I removed the fuse from the fuse block and installed 2 male Flat connectors (after cutting them to match the fuse itself and taping the top so they will not touch or fall out)

2) This is a must...installed an in line fuse 20 amp (factory is a 25 amp) on the positive side of the fuse block to the 30 amp switch.

3) Conected the other wire (switched) to the toggle switch from the other lead comming from the fuse block.

4) Installed the ground lead from the toggle switch to a ground source under the dash (light on the toggle switch will light up once system is energized with switch in the on possition)

5) Tested jumping the ALDL port under the dash and engaging the switch on and off.