so like the title my fan wont go on at temp but it works when i turn on the AC, what could be causing this?
its a 92 3.1 camaro is there a sensor i should be checking?? if so where would it be? or would it be my thermostat? the temp stays down when driving but shoots up in traffic so i usually turn it on by AC switch but even then it wont stay down for long. suggestions welcome and appreciated thanks in advanced

 

sounds like coolant temp switch, in pass head iirc

 

On my 1991 3.1L the temp sensor is on the drivers side head (the front side of it) bumper side of the head. Cant miss it!!!

Theres also a relay on the drivers side firewall to check.

 

You're both wrong... 90-92 cars DO NOT have the redundant fan switch in the passenger's side cylinder head by the lifting eye. And the sending unit in the driver's side head is ONLY for the dash cluster (light OR gauge). The only temp sensing unit for the 730 is the CTS by the thermostat housing.

The A/C system uses an independent fan switch in the pressure line running down the passenger's side frame rail.

The relay would be the first thing to check, but only if the CTS resistance value tests good. Put a wire in the ALDL as though you're pulling codes... The fan should start running while the SES light is flashing. If not, and the alternator is charging (alternator sense wire is on the fan relay circuit), test the fan relay by removing it and swapping with one of the relays next to it and trying the ALDL again. If not, try jumping the red wire to the black/red wire.

:edit: Or, even easier than wiring up the ALDL, just disconnect the CTS. The ECM should automatically turn on the fan with the ignition because it has no idea whether or not the engine is overheating (disconnected CTS makes the ECM automatically assume a temp of -130*).

 

ok sounds pretty strait forward now if you could tell me what CTS and ALDL stand for lol. it wasnt on the list of abbreviations ha so i should just supply power or check if it even gets any right

 

I was just saying that 3.1L dont have the temp sensor on the pass head. Its on the drivers side. Thanks for the correction though on the process of what sensor is used for what.

CTS Coolent tempeture sensor.
ALDL Assembly line data link (or at least thats what comes to mind so i may be wrong..lol)

 

The ALDL is the diagnostic connector by your fuse panel under the dash...

 

Heres what it looks like while were on the subject. This isnt a thridgen pic but its still a OBD1 Gm port.






And since your asking about info heres a link to always keep handy for check engine codes if you dont have a aldl cable to link to a laptop.

https://www.thirdgen.org/service-eng...ht-error-codes

I still need to look and see if aldl means assembly line data link as for some reason I remember it being called that back in the day..lol

 

cool thanks. would the CTS be on the block or better yet can some post a pic of where it would be

 

See that gray intake in the middle of the picture?? If im correct.. the CTS is right there on the front right side by the way your looking at it on the picture. Sorry I dont have a better picture but its just a quick shot to give you a idea. Thats the lower intake manifold. It will have a wire that has a clip on it that connects to the CTS sensor. IIRC the sensor also has a bronze/copper color to it. You can miss is when you look at the front of your lower intake manifold on the drivers side. Hope this helps and not confuses you.

 

Your definition of the ALDL is correct, but it could also be a diagnostic link (for the last 2 words) or the more familiar (for those who know a bit of OBDII) DLC (diagnostic link connector).

The CTS is the round sensor next to the thermostat housing, where the upper radiator hose connects.

 

ok thanks it was pretty easy to spot once i knew what i was looking for just not to easy to fit my big hand between the other stuff to get to it. anyway i disconnected it and the fan came on as well as the SES light just like maverick said. so what does it all mean?? does it mean its not the ECM? i already got a new CTS but havnt installed it yet. is there any thing else i should check?
im thinking i should just do the thermostat while im at it an extra $8 isnt bad. i dunno what the PO has or hasnt done.

 

The ECM turns on the fan once the coolant temperature goes above 228* F. So unless idling for a period of time the fan won't be turned on.

The CTS may be bad and not reporting the correct temperature. This can also occur if the connector for it becomes slightly corroded. The higher resistance causes the ECM to see a lower then true temperature.

So also replace the connector if there is even the slightest sign of corrosion on the CTS terminals. Be sure to solder and heat shrink seal the pigtail splice.


RBob.

 

Also, if you do go to replace the CTS, DO NOT use any thread sealant. Yes, I know that it grounds through the connector, but it's a good habit to get into since the other coolant temp unit actually grounds through the threads into the cylinder head. If you use sealant there, it will fail to ground properly and affect the gauge reading or the working of the temp light in the dash (if you have an idiot light).

 

ok so i changed the CTS and took it out for a spin and still wouldnt go on at temp, i let it go to about 240 then i turned it on with the AC what else could be causing this?? when i unplugged the CTS the fan does go on????

 

This is pretty wrong, you need to use sealant to seal the threads.

I dont care how much sealant you put on there at the beginning, it will still make more than a sufficient connection, even on sending units that ground through the body.

 

OP your gauge is likely just reading wrong, use a laser temp gun, and check temps while the car is running and wait for it to kick them on.

 

i doubt its the gauge cause it rises and lowers when it would seem logical like raises sitting in traffic and goes down when i turn the fan on etc it all seems to make sense when it changes. ill give it a shot just to make sure. do i just aim at the block where the CTS is???

 

Yes it can be the gauge, the stock ones arent very accurate, it can work by moving hot/cold but the temperature be incorrect.

thermostat housing is a good point.

 

WRONG. And wrong. You use sealant, and it WILL affect the grounding of the sensor (actually, the sender, the sealant has no bearing on the sensor since it is grounded by the ECM), period. This is obviously why so many dash gauges are reading wrong. Funny how I've removed a few of these things and NONE of them have had sealant on them from the factory. Also funny how my dash gauge was right on the money with no sealant on the gauge sender.

This is almost like the guys that remove the decklid from the hatch glass to realign the hatch .

 

NOTE: Replacement components must be the correct pant number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

1.Coat the sensor threads with sealer P/N 12346004 (Canadian P/N 10953480) or the equivalent.

NOTE: Refer to Fastener Notice in Service Precautions.


2.Install the ECT sensor.



Try to correct me again smart one.

 

Oh and they do come with sealant from the factory, apparently you just dont notice these things ..

http://www.ebay.com/itm/NEW-GM-Coola...a1598f&vxp=mtr



See that orange stuff, thats called sealant.

Shown here also:

 

Unplugging the CTS is a good test. This tests the ECM driver, wiring and the relay. And shows that it is all good. The ECM 'sees' a very low reading from the CTS and figures it is bad.

It then uses a default coolant temperature and turns on the fan. Turning on the fan is a precaution as the ECM doesn't really know what the engine temperature really is.

At this point in time it would be best to put a scan tool on the ALDL port so that you can see what the ECM is seeing for the engine coolant temperature. That is the defining factor at this point. It may be that the wiring between the CTS and ECM is bad, or that the ECM itself is bad.

Or the dash gauge is way off and the engine temperature isn't really getting high enough.

RBob.

 

thank you this makes more sense

 

What if I wanted to wire my fan direct where would the best place to install it be so when I kick the key on she comes on

 

Bad idea, but just disconnect the A/C line high pressure switch connector. That will cause the fan to run at key-on.

RBob.