'96 Camaro 3.8L (stock)

So I noticed that my fans sometimes come on and sometimes don't. I asked around and found out that two things tell the fans whether or not to come on: (1) the coolant temp sensor, and (2) the A/C being on.

I saw my temp getting a little high yesterday, so I stopped and popped the hood. Fans were off. I clicked the A/C on, and the fans came on. I clicked the A/C back off, and the fans stayed on after that. It seems they come on with the A/C whether it's set to hot or cold, but they don't come on unless the A/C is on, even if the car is too hot.

Any ideas on what the culprit could be? Does this mean my coolant temp sensor is bad? I didn't think it would since it sends the right measure to the guage (I'm pretty sure this model only has the one sensor). Does it mean there's a problem with my PCM? Any insight would be appreciated.

 

The coolant temp sensor (ECT) that causes the PCM to turn the fans on, is not the same as the temp gage sender that operates the temp gage. The fans should come on when the coolant temp reaches 220 deg. Before you do anything, verify that the gage is accurate.

 

I was told that the 3.8L engine only has one sensor that serves both functions. If that's not true, where's the one that tells the PCM to turn on the fans?

I'm almost certain that the guage is accurate, but haven't really tested it. How do you recommend testing that to be 100% certain?

Thanks for the quick reply :0)

 

Since your A/C comes on, the fan relay must be fine. You need to check your Cooling fan switch for faulty one or you can have a bad cooling motor.

Your car should have two sensors, one for the Engine and one for the A/C. The ECT will the PCM to the turn on the fan

 

The only ECT I know of in my vehicle is the one above the water pump. I've been told that controls the guage and sends the signal to the PCM for turning fans on. If that info is incorrect, where is the other ECT and which one performs each of these functions? This is for the 3.8L v6 engine.

The relays are fine. There are three of them that work the fans, and all three are in working order.

I don't think the motors are bad, since the fans come on fine when the A/C is on. They're definitely blowing enough air, too. They just don't come on unless the A/C is on.

Where is the fan switch? I wasn't aware that there was one. As far as I know, the PCM is where the switching takes place, and it sends current to the relays depending on whether the A/C is on and depending on the temp of the coolant. If there is a different switch, I'll definitely test that next.

 

the dual-purpose (pcm an gauge) coolent temperature sensor on the 3800 v6 engine is located under the throttle body.

the 3800 v6 uses a combination sensor that sends to both Pcm an gauge.

check the circuit and gauge operation by grounding the wire to the sending unit while the ignition is on (not running) if the gauge deflects full scale the circuit an gauge are OK the problem lies in sending unit.

to check sending unit ,check resistance of unit when engine is cold resistance should be high about 1365 ohms. next run engine til it's filly warmed up an check resistance again it should now be low 55ohms at 260-degrees F. if it doesn't respond at close to these numbers replace the sending unit

 

Thanks for the info! I'll test it tonight or tomorrow (whenever the rain stops). If the sensor and guages show know problems, would this be a PCM problem?

 

In your original post, you said that the fans come on sometimes and sometimes they don't...which is perfectly normal. You say the temp is getting a little high sometimes. I think the question that should be asked is this....... are the fans coming on when the temp gets above 220 on your gauge? If so, everything is working normally. On my Z28, the fans don't come on unless the gauge reaches almost the 3rd mark, or the one right before the red, then the temp cools down to right below the middle mark before the fans turn off again.

 

Thermostatic Switch should operate the fans. I know the early 4th gens had them. I wonder if the 96+ have them or not

 

You're right, but the fans don't come on at all unless I click on the A/C. If the A/C is off, the car will keep heating up until I start moving down the road (then it gets some airflow) or turn the thing off. It definitely passes normal operating temp if I idle for any amount of time with the A/C off.

I tried testing the ECT this evening, but the stupid thing is a nuissance to get to. I'll need to remove the TB in order to get my multimeter's leads in to it. However, the guage is working fine, so I don't think there's a problem with the sensor itself. I'm thinking it's either the wiring between there and the PCM or it's the PCM itself... <sigh>