Radiator fan doesn't turn on while driving in traffic and the engine gets too hot, say about 220 or more. If i turn on the A/C, the fan turns on and engine temp goes down. Is there an engine temp sensor that is strictly used for the ecm and where is its location? The fan has turned on before when i leave it parked (no a/c on) but when I drive around and pull over, the fan is not on. 92 LH0 3.1L V6.

 

The fan is ECM controlled. Best bet would be to put a scan tool on it and monitor the coolant temperature and fan status. It may be that the CTS is not reporting correctly.

RBob.

 

The fan switch is at the back of the passenger side head, with a single green wire going to it; that's the "non-computer" fan turn-on that goes right to the fan relay. That should kick in at 230 degrees... make sure that sensor's all hooked up OK and its wire hasn't been mangled/burnt/etc.

 

Tom, the 3.1's don't have the fan switch, just the 2.8's.


firebat, missed part of your question. The ECM coolant temperature sensor is on the front of the intake manifold. Has two wires going to it.

RBob.

 

For once, tom is wrong. Rbob is right.

Now, heres something more to confuse you. The gauge in the car may not be reading right because that one does take a different sensor, that is in no-way related to the ecm/fan. So it may be wrong and reading over/high. While the sensor for the ecm/fans is reading properly.

If all else fails, it is quite simple to hook up an over-ride toggle switch so you can turn it off/on when you want.

 

Are there resistance tables or something that I could go off of to test both of the temp sensors to see if they are in acceptable range? Resistance vs. Temperature table?

I've had problems in the scorching heat of summer where the car actally stalls or bogs out no power to go above 1500 rpm. I was told once it might be the injectors but now i'm thinking a temp sensor might effect it. Very rarely does this though. One summer it never did this at all. It didn't help that the car got overheated b/c no fans turned on. Any chance that a temp sensor could cause this condition of loss of power?

 

IMO its very possible that if the heat got to hot it would change the pulse rate of the injectors would change and cause power problems.

Search on here for the ECT chart, I've seen it posted. If you cant find it, I'll pull my book out and scan it.

As for the coolent/dash sensor.. Um, not sure on that one. HAvent seen a chart, but its possible.

 

not to be rude or any thing but yalls have been telling me that i should have a fan switch since i first started asking about this same problem a long time ago, yet I have searched the whole wiring harness on my car and guess what? no fan switch. there is only one wire going from the fan relay to the ECU and no hint of the wiring having been tampered with. I have a plug in the pass side head where this switch is supposed to be and there is not a connector hanging loose either. i have asked people with 2.8s to post a pic of this yet it never happens.

 

Early 2.8's have a fan switch in the passanger head.
Late 2.8's are questionable.
3.1's have no fan switch, it is in the ECM.


If you have a connector hanging there, then someone before you has removed it.

 

Oops, didn't know that about the 3.1! Thanks RBob!!

 

With the '85 being a 1 year only ECM I wonder if that ECM has control of the fan. It just may be why there isn't a switch there.

The '86 through '89 years used a different ECM then the '85 year. The '90 - '92 use a different ECM again.

RBob.