hey guys, i recently did an intake manifold gasket and did some cleaning and everything was working fine before i did this on my 1991 camaro 305 TBI. now when i run the car it will get up to 240 degrees and my fan will no longer turn on. it worked fine before and im not sure wat the problem in. the fan turns on when i put the A/C on though and i put a new thormostat in it last summer. i think it could be the relay. any ideas? or should i just replace the relay seing it is only like 10 or 12 bucks? thanks guys

 

sounds like a relay. maybe it accidently got unplugged make sure you have all ur connections pluged in. then i would try the relay.

 

make sure you did not accidentely disconnect switch on pass. side cylinder head . it's between 3rd & 4th plugs on passengers side . single wire lead going to it . good luck .

 

okay thanks guys, i didnt rouch anything on the head but ill check it out just incase anything happened to it but i thing im just goin to replace the relay, its the original so it could be bad. its cheap and something i want to make sure its not the problem so im replacing it. the cars almost 20 years old so better tobe safe than sorry right? im thinking it also has a bad headgasket. idk what to do about that either,maybe sell it and get a new camaro or keep it and maybe try to fix it when it gets nice out? this massachusettes weather sucks, so im not sure. thanks again

 

Check you're dipstick sometimes if its a leaking head gasket it will be a milky substance on the disptick or bubbles.

 

heres the thing, the oil is fine. i did an oil change right after the manifold gasket (a couple of weeks ago) and there was nothing in the oil. it was just dirty, but it also passed a block test and i tested the radiator with a coolant pressure tester. its gona be a pain but i havent done a compression test to each cylinder. ishould really do it but its gona suck.the car runs good but a pretty good amount of water still leaks out of the exhaust. its killing me because i =ve had the car for over a year, it was my first car/camaro and ive puut alot of hard work and money into it so it kills me that it is like this. i dont know wat to do now besides the compression test

 

Take a deep breath.

I'm experiencing the same thing with my 86 T/A. It is the fan switch on the pass side between the No. 6 and 8 cylinders, underneath the exhaust manifold. My lead had melted off and the top of the temp sender had broken off. My fan will only operate with the A/C switch on. Your local auto parts store should have them.

Additionally, it is a PITA to get to it. Mine requires a 13/16 socket to remove, but I have
no room to move the tool. Can't get to it from the top due to the space and the oil dipstick tube in the way. I may just wire it to the temp sensor on the left side and see if that works.

Jim Berry.

 

alright, i checked it out and it looked fine, both the relay and the switch are inexpensive so i will most likey like replace both to be same. the relay is easy to take off and replace so i will do that first, this is where all my suspicion is so ill start with this. if it continues to not work ill change the switch, thanks for the tip =)

 

so today i got the new relay and it did nothing,so i guess its time to get the fan switch for the head on the passengers side. does anyone know how hard or long itll take me to do it?

 

If you need easy access to the passenger side head, I would suggest pulling the spark plug wires and the plugs(if theyre in your way), unbolt the A/C compressor rod support, then look for the radiator pipe that runs from your radiator hose by the radiator cap to the rear of the motor-it has little screw clips holding it to the body(remove the screws to move the pipe slightly for more clearance), removing these things may give you enough room to get to the switch.

The next thing to remove and trust me it is a pain to do without breaking it is remove the passenger side AIR pipe from the exhaust manifold. I did mine recently, 14mm socket, 14mm crow foot, 14mm wrench, 9/16 socket and wrench were the tools I used. If for some reason you dont care about breaking it, cut the pipes short near the bolts with BOLTCUTTERS(easy) or snips(more difficult) USE LIQUID WRENCH. end rant.

With the water in your tailpipe, its possible that your intake gasket install has a leak even if it was present before you did the gasket swap-things are never perfect. A head gasket job isnt really all that bad to do if you can take the car out of service for a week or so until you can complete the job. Gaskets,scraper,gasket remover or acetone/paint thinner and possibly new bolts/torque wrench is all you really need.

As for the fan, replace switch, relay, make sure all electrical connections underhood and all fuses are good, then take a look at the fan motor itself. Sometimes with these older cars, the wiring gets old and a small short somewhere can cause big issues. I plan to redo my underhood harness completely very soon due to similar conditions.

GL

 

I can't figure out my people have a hard time replacing that switch, it was fairly easy on mine. I done it from underneath the car. Be prepared to get soaked with coolant when you take it out though, take a big bowl or something under there with you.

 

yeah i was gonna go from under the car too, thanks for the warning. ill drain it first too, thanks for the tip =)

 

I used AC Delco switch #D1855B on mine, it's a lower temp switch that turns on at 215 rather than the stock 238. It's works great on my 350, but I'm not sure if the 305 is the same (I think it is).

Use a little plumbers tape on the threads too to make sure it doesn't leak.

 

where did you buy it? i cant seem to find it. also, how much was it? thanks

 

http://www.oehq.com/acdelco-parts_D1...e%20Sensor.htm

 

i have a question. if it was my coolant temp sensor, would my temp gauge work still? because it works and id just like to know so im not spending money if i dont need to.

 

I think the gauge would still work if you had a bad CTS. The CTS tells the computer the engine temp, I don't think it has anything to do with the gauge.

If you have a bad CTS it could be causing the primary fan not to come on since it's controlled by the computer, but it's not tied into the aux fan. which is controlled by the switch in the head.(I'm assuming you have dual fans?)

If you have a single fan I think it's controlled entirely by the switch and not connected to the CTS or ECM at all. Maybe somebody else will back this up.

 

sorry should have specified, single fan. so i should just replace fan switch?

 

Just to clarify a few things:

If your fan comes on with A/C then the relay is working perfectly fine. Both the A/C switch and the temp switch enable the same lead on the relay.

I'd recommend using teflon sealant on the temp switch. The switch relies on conductivity through the threads to the heads. Teflon tape may insulate the threads. If you do use tape, check continuity between the switch body and the block.

The single fan is controlled by the temp switch on passenger side head. Guage sender is on opposite side head. The CTS for ECM is separate.

Before replacing the fan switch, double check the temp switch sender wire. Disconnect it from the switch and jump it to ground-the fan should come on (with engine in 'run'). It's much more likely that the sender wire was damaged during a manifold swap than the temp switch picked that moment to expire.

 

okay, thanks for the help todays pretty crappy here in mass. so i most likely will get to workin on it tomorrow. ill post my results ASAP.

 

Well... I only read half of these articals but it sounds like im having the same problem...but with some problems added on. So the fan....does turn on at 240-250 roughly but when i start the car the temp sensor goes haywire (redline and past) and when i turn the A/C on it also goes past redline. Im not to experienced with cars and their electrical systems (im a motorcycle person) so I need some help and i know that the car had overheating problems before i bought it so the dumb$#%^ put in a ground he could just manualy turn the fan on by touching two wires together under the "hood" (there was no hood).
Well if that explains anything and someone knows whats going please help. Thanks

-D

 

i dont know man, maybe you should use his silly setup and just put a switch in the car to just manually turn the fan on. a lot of ppl on here are doin that just because they want to make sure their car doesnt over heat. theyll turn it on around 200-220 or right wen the car is started. i usually turn my ac on around 200-220. but if i were you, i would probably start replacing most of the things if i had the money cus a lot of the things, sensors and the relay are like 12 bucks lol. it is and older car so wen i have a problam i like to take care of things that could be the problem or sumwhere down the road could cause that problem. know wat im saying?

 

Make sure the temp guage wire is connected to the correct sender on the driver's side head. I would condone a switch, but ONLY if it is installed IN ADDITION to the fan temp switch. Someday, someone is going to forget to turn it on and running the fan constantly is a waste of energy (gas) and can be an issue in the Winter with warm up.

 

check the fan temp switch that is on the passenger side in-between cyl. #7 and #8. the sensor that controls the temp gauge is in-between cyl #1 and #2 on drivers side and has nothing to do with the fan. the sensors are different in that the fan sensor is a thermocouple that closes at 196 deg. thus completing the circuit to the ecm, the fan should turn on at approx at 196 to 220 deg. the temperature guage sensor is a variable thermocouple that reads temp by resistance, it sends the resisted signal to the temp guage thus reading the temp, im not sure if it sends any signal at all to the ecm.
yes the fan sensor is a pita to get to!! best done from under the car. if you remove it drain the radiator first you can test the sensor by shoving a test probe up the fan sensor wiring connector and grounding it. once grounded the fan should run with just ignition on. if the fan doesn't run the problem is most likely not the fan sensor, it is elsewhere. also when you ground it, even if the fan doesn't turn on the relay should make a clicking sound. if there is no clicking then the issue is elsewhere in the circuit or the relay is bad. probing the 12v into the relay should tell you if the relayis recieving power or elsewhere. another place to check is the fuse-able link for the fan system. if you do have to wire a switch into the system it is easily done at the ecm. I personally dont like switchs they are prone to human failure

recently i bought a 89 Camaro that had fan issues with both fans. the original owner had direct wired the fan and his work was bad to top it off. the problem ended up being the fuse-able link. it drove me nuts and a club member came over and finally found the issue. much gratitude to this fellow member. I hope this saves you some time and brain cells.

 

The fan switch is not a sensor. It closes to ground at 238°F and has nothing to do with the ECM at all on a TBI car.

The part for the gauge is a temperature sender, not a sensor either.

naf has already stated the best test procedure and 80schild is correct about the fan not being operated by the ECM (for TBI).

The Autozone equivalent for the Delco switch is sw505

 

yep its a : thermistor : And if you want read this article http://www.superchevy.com/tech/0502s...ing/index.html do it! if you want stock, order the wire connector too. its worth it. perform a western union tie solder with heat shrink

 

Wow...no surprise, Super Chevy magazine is whoring out misinformation. Must be nice to tell the masses wrong information for promoting a company's product and recieve money for it.

Nice link... to bad it is s--t for any useful information.

If anything, the fan switch is a thermostatic switch. It is a on/off switch controlled by a set temperature.

 

ill stand corrected

 

I'm not trying to be an an -ss to anyone (my apologies if it comes across that way) but, it seems that bad information is the only thing that ever seems to get spread around or, found in a search.

The same bad information still floats around the website about the oil pressure switch being a safety feature. I have corrected that misinformation numerous times as well as others but, somehow, the correct information gets buried and the incorrect information continues to spread.

 

np... im not concerned,good info is definatly better than bad any day. i was trying to help and tbh my specialty is not auto wiring, im a machinist/programmer by trade. you wouldn't believe the amount of poor information out there on that subject lol. inbetween the lack of interest in the youth and outsourcing, it is a trade that is rapidly being lost.
I figured that due to tpi wiring diagrams and what info i gathered though manuals and even this forum, that the ecm had to do with this. I did not realize that tbi was different. last tbi system i played with was hand built for a jet ski lol. nothing like running 100mm of throttle body on a 750cc jetski
to me a thermistor is a form of sensor, at least in a rudimentary sense of the term. trust me finding the fusable link being bad on my car was not fun, I hate electrical systems with a passion