Electric fans not working? Any ideas?

ok, i purchased this car a couple of months ago, did the whole tuneup thing 97 3.8l w/ 5spd manual i did manage to get 3 plugs from the top though. my problem is when i started driving the car i noticed the temp rarely moved past the 160 degree mark, me being in tennessee in the fall i figure thermostat stuck open. i purchased a 180 degree thrmo instead on the 195 degree. installed it and found i was correct when i removed the old thermostat. my temp now runs about 180 degrees during my cummute, but when i get into traffic i noticed it climbing to 210 or better(Oh SH*T my first reaction) as i traveled a little it went back down. i found the fans are not kicking in, was going to turn the a/c on and see if they would come on as they are suppose to but the a/c is inoperable(i will have to fix it later but winter is here and im not worried about it right know.) i replaced all three relays and checked the fuse at the junction box under the hood, still nothing. please tell me its not a commin thing for the pcm to malfunction and ground out the relays for the fans. i havnt replaced the temp sensor as the gauge is working fine and all the schematics i have seen do not show the temp sender to work the gauge and the fans, although it is a three wire sensor. from what i can tell from the schematics the pcm reads temp from the sensor and grounds the relays. if there is another sensor that controls the fans please let me know. or if you have any other ideas im game.

The Engine Coolant Sensor is what the PCM looks to for the coolant temp. The sensor can go bad without setting a code. You can verify if the PCM is getting a reasonable signal, by using a scan tool & reading what temp the PCM is seeing. Comapre that reading with what the temp gauge is showing. If the temps are more than 15 deg apart, put in a new sensor. If the temps match, you will have to find out why the fans do not run. Check the fuse powering the relay winding, and the fusible link providing power to the fans.

just run a direct hot to the fans and tie into it with a toggle switch.

That is what people do if they can't find the problem. But the other problem is that if the temp sensor is bad, it gives the PCM the wrong info, and the PCM pays you back with the wrong A/F mixture and possible loss of power.
Chad, not to get off the subject, but I like the color of your car, is that one of those paint jobs that change color when viewed from different angles?

yea it changes from like green to blue and a couple of other colors depending on how you look at it.

Yeah, i work for Detroit Diesel -allison as a diesel mechanic & Transmission tech. so the only scanner i had was a snap-on and it was close to the gauge temp. i didnt pay too much attention to how close it was from the temp gauge but my scanner said the temp was up to 215 degree at one point and the fan still didnt kick on.
As for running a toggle switch i would think about that for situations where i wanted to control it manuallly, but i don't like to jerry rig stuff. I want it to work as designed and not just go to the simple but tacky way of doing things. i figure since the scanner temp is pretty close to gauge temp the sensor is fine, i know some cars had a two sided temp switch one side to control fans and the other side feeds pcm and gauge but wasnt sure if this one worked that way. if its not the sensor,relays (which i have replaced), fuses it has to be a corroded terminal at the pcm or the pcm itself, unless anyone knows of a alternate sensor for the fans only. i guess i will check the terminals at the pcm next and if thats not it maybe find another used pcm and have it reflashed at local dealer. we do favors for them all the time since the new trucks run the allison transmission and thats what i work on, maybe i can talk them into doing it for free if i find one. worst case i have gotten new parts at real low prices from them and maybe the pcm wont be too bad if that turns out to be the culpret.

Might sound like a stupid question, but have you checked the ground for the fan motors? And the blades spin free?

I learned the hard way, check the simple stuff 1st, it's cheaper.

the fans work when i jumped the relays also i jumped the a/c pessure switch and they came on. it seems like the pcm is not going to ground when the temp comes up. i pretty sure that the pcm grounds the coil in the fan relays to turn them on so in my mind it seems that it has to be the wire from pcm to relays or pcm unless its coolant sensor, i dont think its the pcm because when i jump the high side pressure switch the fans came on which means the pcm is controlling the relays. the only thing that baffles me is its not requesting them on except when it sees the a/c pressure switch closed. they are supose to come on when the engine is off and engine temp is above 140 degrees and they are not coming on. i think im just going to purchase a temp sensor and give it a shot, although i dont like to throw parts at it until i have verified that its the problem.

Before you through a pcm in your scanner should tell when there is a fan request. I have the Modis and have done this before.

I think you found your problem. No AC charge. ("the fans work when i jumped the relays also i jumped the a/c pessure switch and they came on") GM has the AC engage when the heater is in the defroster mode to remove excess moisture from the incoming air. Below 28 degrees (outside air temp) there isn't enough humidity in the air to need this feature. A co-worker had the same problem with a '97 Fbird. Charged the AC and the fans worked.

You can jump the low side switch and pull the AC relay (to prevent compressor damage) until a proper fix can be done.

yeah, i just put some dye in the a/c and 1 can of freon to check for leaks before did a total charge on it. when the engine temp got to 225 degree the fans started working. i was thinking that might be the problem from the start but wanted to checked everything out first, seeing how its december and i would need the a/c until spring i was going to wait but i grabbed a few cans from work and came home todays and charged the a/c system and the fans started working. i thought i read in the manual they would come on if the engine temp was over 140 degrees and engine off, they still wont come on when the engine is off, unless it was a typo and its suppose to be 240 degrees which sounds more realistic to me. either way they are working now and i appreciate all the help, i like to pick everyones mind before i tackle something like that because more than likely someone with the same setup has been there before me and could point me in a faster troubleshooting process. thanks again.

So your radiator cooling fans wont work when the temp rises if the a/c is undercharged. That makes no sense.

I agree.

But remember, this is from the company that brought us the Vega. Now THAT was an engineering masterpiece.

i am with you its makes no sense at all but it is what it is. i know they are suppose to come on when the a\c pressure swith closes and when defroster is on but actually that is the a\c coming on causing them to come on there. i will say this i don't know whether it was Coincidence but beforei charged the a/c i yanked the pcm and tore into to it, wanted to check for burnt circuit. i mean i tore it all the way down, sprayed the connector and pcm terminals with contact cleaner and reassembled pcm. i don't don't know which was the actual cause but its fixed now. thats why i don't like to do too much at once, so i know what the actual problem was.

I had learned to expect that kind of nonsense from dodge. I was working on a k car and found the fan would only work while you pushed on the gas. Let off and the fan would stop. I problem might have been unnoticed if it worked the other way around.

quote:

ORIGINAL: 01 Camaro Cp

I agree.

But remember, this is from the company that brought us the Vega. Now THAT was an engineering masterpiece.

HEY!
That water pump/timing belt tensioner was genius. It combined two parts into one thus saving weight. Like the aluminum block.

Personally I wish they would have installed a fail safe for the fan system. But I guess on paper it's not needed.

Don't know how closely you've worked with design engineers, but some of them are so 'into the numbers' they can't see the what the average Joe can smell. Then again I really think some of them have a secondary degree in fianance .... "How can we design in a set amount of failure and desired profit?" Don't get me wrong, I'm not bashing just auto engineers, just all of them without some common sense.

Personally, the best engineering goof I think I ever had to work around was the Renault R16. Someone forgot that during a normal service you might want to remove the valve cover to do such little chores as valve clearance adjustment .... They issued a TSB with the offical hammer partnumber and a diagram showing where to apply this device to the firewall to get sufficent clearance to remove the cover. Imagine what the customer must have thought when they saw the tech beating the hell out of their new car at the 1st service. And to top it off, wasn't any labor allowed to do this.

i know exactly what you mean about the valve cover issues, i work for a Detroit Diesel Distributor as a lead transmission tech. and also work on the engine side when tranny work slows down. i don't know if your familiar with big rigs but on some model GM White Volvos you have to unbolt the front cab mounts and jack the cab up with a porta power to remove the valve cover, its let say, SH*T.
i mean we are talking about a 18 wheeler or tractor if you will, the hood rolls forward and bam there is the engine, better yet you have the T2000 that you have to remove the coolant resevoir,rain tray, fenders and and a whole bunch of other crap just to see the engine, and we are talking about a 60 series engine here the freakin thing is bigger than my camaro. however, that is the truck OEM and not detroits doing, they have some sense about them as far as the electronic goes. the fans on these big rigs are controlled by a air clutch and if the circuit fails its default is on all the time which does rob horse power and torque but it does stay on instead of not coming on at all. the computer has to contol it off, so if something goes wrong with the fan circuit you pretty much know it because it wont go off.

Agreed, Minerman.  I work for a local Diesel shop and have noticed exactly what you've mentioned.  The T2000, as nice as it is, is a heart attack to work on, as is the majority of any Volvo manufactured truck. A fellow tech just finished a clutch job today on a Volvo dump truck.  He's an older guy and the thing almost gave him a coronary!  Hydraulic clutch lines, retarded dog-box placement, and terrible ground clearance made for a week long job. Detroit sure knows how to build an engine, though.  Cummins and Cat are really getting low-grade, IMO.  

usarmyrangrs, just wait until '07 i believe the new '07 detroit 60 if you want to call it that is going to be a royal pain the arse. common rail system,egr can't get to nothin, junk. well, since dymler chrysler bought detroit, they thought they should breed the MBE and the 60 series and it looks like the offspring is going to be a BLUE TURD. i have seen pictures of it and it looks nothing like a 60 series. they really made things too complicated when they added egr to the 60 series, not the egr system itself but the electronics part of it. i kinda reminds me of the 1k/2k series allison when they first came out with it, 1 problem= 15 codes. i just treat it the same way though, write the codes down if not active and clear them, then drive it and see which one pops up first. sorry, i know this isnt a diesel forum but i thought you may want to know whats coming down the pike.