94 3.4L cooling fan problem

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

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.

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/?action=vshop&vid=5&pcid=96

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.

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.

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.

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

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.

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

Got it and responded!

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.

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.

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?

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.

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

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.

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?

It's heating all the way to 260 and the warning lights are coming on. I got the water pump pulled this evening and stopped. The water pump is easy, but getting the darned PS out of the way is a pain. The auto parts shop had to order the ECM from Houston (despite telling me over the phone that they had one in stock) and it won't arrive until Friday so I decided to go ahead and do the pump tonight and tomorrow night. I'll just be able to drop the ECM in on Friday evening and we'll see how it goes. Another tidbit about the ECM - they say they have to "flash" program based on the VIN before they hand it over.

Okay, I have an update for those who might be interested. As planned, I bought a new ECM and installed it. The fan still does NOT come on and the temp gauge was still pegging out. I decided to take the radiator off and have it professionally cleaned and the temp still pegged. So, I have a cleaned radiator, new water pump, new temp sensors, new thermostat, new ECM...basically anything to do with the cooling system has been cleaned or replaced. I then decided to replace the already new thermostat with yet another one - this time a 180 degree version instead of the 195 degree model. I started the car and let it run with the radiator cap removed and watched it. As the temp gauge climbed towards 235 degrees, the thermostat opened. and the car stayed between 235 and 250 on the guage. My diagnosis now after all i've been through - the temp gauge in the dash has gone bad and is reading between 45 and 50 degrees too high. This explains a lot of things including the fact that the fan still does not come on - the ECM is getting the correct operating temp - around 200 or 210 degrees while the guage is misinterpreting the temp as 250 degrees. The ECM sees no reason to kick the fan on. Not surprisingly, we've known the gas gauge to be wrong for quite awhile. So, what I'm thinking is the dash gauges are crap and i've replaced the entire cooling system for no reason as a result. The only consolation is that I won't have to worry about the cooling system anytime soon.

Okay, I have an update for those who might be interested. As planned, I bought a new ECM and installed it. The fan still does NOT come on and the temp gauge was still pegging out. I decided to take the radiator off and have it professionally cleaned and the temp still pegged. So, I have a cleaned radiator, new water pump, new temp sensors, new thermostat, new ECM...basically anything to do with the cooling system has been cleaned or replaced. I then decided to replace the already new thermostat with yet another one - this time a 180 degree version instead of the 195 degree model. I started the car and let it run with the radiator cap removed and watched it. As the temp gauge climbed towards 235 degrees, the thermostat opened. and the car stayed between 235 and 250 on the guage. My diagnosis now after all i've been through - the temp gauge in the dash has gone bad and is reading between 45 and 50 degrees too high. This explains a lot of things including the fact that the fan still does not come on - the ECM is getting the correct operating temp - around 200 or 210 degrees while the guage is misinterpreting the temp as 250 degrees. The ECM sees no reason to kick the fan on. Not surprisingly, we've known the gas gauge to be wrong for quite awhile. So, what I'm thinking is the dash gauges are crap and i've replaced the entire cooling system for no reason as a result. The only consolation is that I won't have to worry about the cooling system anytime soon.

Well about the gas gauge.. Does it read full for a long period of time, and then suddenly start to drop pretty quick? If so, that's normal. Its due to the gas tank being shaped like a "V" and there being a mechanical sensor, rather than a computer controlled one which would give you a more accurate reading. Most newer cars come with the computer controlled one. And as for the fans... I'm sorry to hear that you went through all that trouble and it's still not coming on. Only thing I can suggest is that you get a manual fan switch and just make sure your daughter keeps it on. I really doubt that the temp gauge is your problem. Because that just shows you the reading that the ecm is transmitting to it. So if the gauge were to be wrong, than so would the ECM (which in your case is brand new and shouldn't be).

Well, my understanding of the temp sensor, temp guage, and ECM set up is a little different than what you describe. My understanding (I could be wrong) is that there are two sensors (this I know after replacing both) one of which signals directly to the dash gauge and the other which sends the temp info to the ECM independently. I think the only way to confirm my suspeced gauge issue is to come up with another way to measure the temp to compare against the gauge. I'm basiing my assumption on the fact that I have a 180 thermostat (new) and it's not opening until the gauge is reading 235. I'm still inclined to believe the gauge is bad.

As for the gas gauge, it used to act as you described - dropping slowly and then accelerating. Now it's dropping to about 1/2 and then stays there until you run out of gas. My daughter has to use her trip odometer to know when she's running low. My son's El Camino does the same thing at the 1/4 mark. Of course, other than running out of gas at an inopportune time, it's not nearly as big an issue as the engine welding itself shut do to overheating.

Hmm, you could try buying a single temp gauge (such as an APC one from AutoZone), hook that up and see if it reads the same temperature. That would pretty much narrow it down to the dash temp gauge if it's the problem. Then you could return the one you bought if you don't wanna keep it.

Ok Im Wondering If This A Problem With This Type Of Motor The 3.4 L Cause I Have The Same Problem In My 95. And I Did The Same Thing You Guys Did Replaced The Thermastat And Put One That Opens At 160. Flushed Raditor Changed The Water Pump Etc.
So What I Did Was Disconnected The Gage That Tells The Fan To Come On At A High Temp So Now It Comes On When I Cut The Car On And Cuts Off When I Cut The Car Off And The Car Never Goes Pass The 167 Mark. The Only Prob I Have Is That My Check Engine Light Stays On Do To The Fact I Disconnected
That Sensor. But It Runs Well. In The End Im About To Put A Fan Switch So Idont Have To See That Check Engine Light

you checked all the fuses. but what about the rust colored fusible link around the positive battery terminal area?