94 3.4L cooling fan problem

[mmac]

Okay, I have read a lot of threads on this subject and unfortunately I haven't seen anything I haven't tried. My problem is that the cooling fan on my daughter's 94 camaro 3.4L is not coming on at all. I have done the following to check it:

1. Replaced both heat sensors in the manifold - the one that sends a signal to the guage and the other that sends the signal to the ECM (I think).
2. Replaced the relay for the fan motor. Thinking maybe that the new relay was faulty I took it back to the parts store and they tested it and confirmed that it IS working.
3. Checked all fuses - all good
4. Jumped to the fan motor to ascertain whether the motor is working or not with power - it does work.
5. Checked the voltage to the fan after the engine reaches a high temp (yes, it is on the verge of overheating so the temp should be high enough to kick the fan on). There was 0 voltage reaching the fan motor.
6. Unplugged the harness from the fan motor and checked the continuity of both wires - the hot wire to the relay box and the ground to the car body. I had continuity in BOTH so it's not that wire harness.
7. Checked the voltage coming into the relay box. As expected, 12v on two of the leads and 0 on the other two.

Summary of the situation - the fan motor is good, the sending units are brand new, the wiring seems to be intact based on tests, and yet the fan motor does not come on under any circumstances.

I'm inclined to believe (based mostly on posts here) that the problem is the ECM. Have I missed something else that could be causing the problem? If the ECM is my only remaining possibility (as I believe it is at this point), is there a way to check it out or do you have to replace it and cross your fingers?

Any help would be greatly appreciated!
Mark

[ct91rs]

Sounds like a problem with the ecm to me. You've covered everything pretty throughly. I don't know fourth gens very well, so I'm not sure whether there is a cooling fan switch, or whether the ecm determines when the cooling fan should come on based on the voltage coming from the coolant temp sensor. If it reads off the temp sensor, I'd say that it must be getting a signal or you should get a code (temp sensor low voltage)and as long as there is no interruption in the wire from the ecm to the relay, I'd say it must be the ecm.

[ViperJ]

I am not sure what to tell you, the only thing I can think of is buying a manual fan switch for a quick fix. SLP has one for our cars www.slponline.com or http://www.thunderracing.com/catalog...&vid=5&pcid=96

[blindeyed]

Might possibly have a bad thermostat? First, do this.. Turn the car on, let it run for a second, and then double check to see if the fans are still not running. If they aren't, then turn the A/C on, and check again to see if they kicked on. If they did kick on, then there's your problem right there, the thermostat. Electric cooling fans are thermostatically controlled and engage whenever the air conditioning is turned on or when a probe mounted to the radiator reaches a specified temperature (195* in your case). Since you pretty much checked everything else, that would be my last guess. You can get a Jet performance 180*, or a Hypertech 160* thermostat for $16 at the link below. Which both are alot better than the stock one which is 195* (so the fans will kick on sooner):
http://www.ftpp.net/V6ExternalEngine.htm#Thermostat

If the A/C does not turn the fan on, then I would say that the ECM is your problem. And I'll tell ya what, if the above solution doesn't work, then I can hook you up with a deal. I just so happen to have a used ECM sitting in my garage from the 2nd 3.4L engine I bought. From what I was told, it is in perfect running condition. Actually, I can just swap it out with mine and double check to make sure. I'll sell it to you for $15 + s&h. And if it doesn't solve your problem, then you can just send it back and I'll refund your money. It's a win-win situation. Especially since ECM's can range from $40+ on eBay and some sites. Just let me know if your interested.

[blindeyed]

Oh, forgot to mention, you could take the car upt o Autozone, or Advance Discount, and have them run a diagnosis on it to see if the ECM is throwing any codes. Might be able to tell ya what's wrong.

EDIT: btw, if you do happen to do this, then be sure to let them know (if they already haven't figured it out) that you have OBD1.

[mmac]

Thanks for the replies! Blindxeyed, I did forget to mention that I had replaced the thermostat as well. I ran the AC-on test as you suggested and the fan still does not come on. I would be interested in the ECM you have laying around. My email is [email protected]. If you want to send me a message there we can work out the details. I can provide you with a FedEx number as I need to get this resolved a.s.a.p. since my daughter relies on this care to get to school and work.

[BiH]

mine did the same thing,only way I fixed it:installed a manual fan switch

[blindeyed]

Originally Posted by mmac

Thanks for the replies! Blindxeyed, I did forget to mention that I had replaced the thermostat as well. I ran the AC-on test as you suggested and the fan still does not come on. I would be interested in the ECM you have laying around. My email is [email protected]. If you want to send me a message there we can work out the details. I can provide you with a FedEx number as I need to get this resolved a.s.a.p. since my daughter relies on this care to get to school and work.

Sent ya an e-mail. Let me know if you didn't get it.

[mmac]

Originally Posted by blindxeyed

Sent ya an e-mail. Let me know if you didn't get it.

Got it and responded!

[ct91rs]

Originally Posted by mmac

I ran the AC-on test as you suggested and the fan still does not come on.

That's interesting...I thought that turning on the A/C sent aseperate (independent from the ecm) voltage to the relay to turn on the fans.

I'd like to hear what happens with that ecm from blindxeyed.

[blindeyed]

Originally Posted by ct91rs

That's interesting...I thought that turning on the A/C sent aseperate (independent from the ecm) voltage to the relay to turn on the fans.

What it does is it sends a seperate signal to the ECM which in turn kicks the fans on. What it lets you know is whether or not if you have a bad thermostat, ECM, or what not.

Originally Posted by ct91rs

I'd like to hear what happens with that ecm from blindxeyed.

His daughters Camaro ended up having a manual tranny, as with the ECM I have is for an automatic. Two different ECM's. So he's going to try to find a cheap one and try it out. Why, you interested?

[ct91rs]

Originally Posted by blindxeyed

His daughters Camaro ended up having a manual tranny, as with the ECM I have is for an automatic. Two different ECM's. So he's going to try to find a cheap one and try it out. Why, you interested?

No, but thanks. I'd just curious as to whether his ecm is the problem or not.

[blindeyed]

Yeah, I'm wondering that myself. It'd be a shame to spend the money on it and still be having the problem.

[mmac]

I'll let y'all know how it goes. I will be picking one up this afternoon and installing it this evening. If it works, I'll be pleased. If not, I'm going to have to drop another dime on a manual switch. I'm also going to swap out the water pump soon because with or without the fan the motor is heating up too quickly.

[blindeyed]

Originally Posted by mmac

I'll let y'all know how it goes. I will be picking one up this afternoon and installing it this evening. If it works, I'll be pleased. If not, I'm going to have to drop another dime on a manual switch. I'm also going to swap out the water pump soon because with or without the fan the motor is heating up too quickly.

At what degrees has it been heating up to?