i have a 92 z-28...my fans wont turn on...i replaced the temp sensor and tested the fans, they work.....any1 have any ideas?????? its a 5.7 350.

 

not sure what you mean by "tested the fans and they work", but if you mean you hooked them directly to a 12V power source, then you could have a blown relay. Follow the power wire from the fan and test before and after every connection. When you find power, you'll know what blew.

 

yes i tested the fans w/ a 12v source

 

There is a fans fuse in the box, check that. Which temp sensor did you replace? The one in the passenger side head controls the fan.

 

i replaced the one that is right in front of the motor...its below the intake in the front...smack dab in the middle.....when i keep the wires un-connected to the sensor one of the fans will actually turn on....??????????????????????????????????????????

 

That is a default setting, part of the limp home mode. The computer completely controls one fan and the other is controlled by a fan switch on the passenger side between sparkplugs 6 and 8. The wire may have come off preventing it from working.

 

dont see a fan switch near these plugs....i appreciate all the help ur trying to give me. shouldnt both be controlled by the sensor though. Both still dont work w/ it plugged in.

 

The switch can be hard to see. To test the circuit you can unplug the A/C pressure switch on the line down near the manifold and jump the wires with a coat hanger. When you turn the ignition on, the fan will come on. This will at least allow you to test the circuit.

 

I just went out and bought the fan switch, i read its near the heat sheild below spark pugs 6 and 8, and a new 160 thermostat...i will replace them tomorrow and hopefully the fans will work....i read that 160 thermo was good to have.

stupid ?......the fan switch will control both fans based on the coolant temp. correct? I've read that the secondary fan will activate when the ac is turned on. My AC doesnt work though...will it needs a recharge(i hope thats it).

any1 have any other ideas incase this doesnt work?????????? ill update tomorrow

 

The fan switch controls the secondary fan. The computer controls the other. If temporarily ground the wire to the fan switch it will run the fan. You need to make sure the circuit is good. This will let you know the relay is good.

 

I did it the easy way and wired my fan to a switch.

 

You may need to replace the fan relay and possibly tha AC fan relay as well. When I got my 91 last year the previous guy ran a swith to the fans since he could not figure it out. The fan relay is located on the firewall near to the fender. The Ac one is located on the other side of the firewall. When you turn on your AC does your fan come on then? If not then most likely both are bad. It will have nothing to do with the sensors in the heads or intake manifolds.

 

There are three relays on the drivers side 1 fuel pump and two fan relays and 1 on the A/C box. They all interchange. You could swap them around and find out if one is bad.

 

i checked all 3 relays on the drivers side w/ the one on the passenger side...they all worked. Im changing out the fan switch this morning ill let u know what happens. If this doesnt work is there anything else it could be???????

 

found a break in the wire for the fan switch right near the motor. Prob tapped b/c the connection plug fell apart in my hand. plus the plastic on the switch, well its not there, must've melted off. Heading to the store for connector. Seems like this is the prob.....i will let all u know if it works at the end of the day......im working slow in this AZ sun(100+ @ 11:00)

 

I have the same problem with my single cooling fan not coming on automatically. I brought it to a garage who suggested the ECM's programming was fooled with and no longer controls the fan...anyone heard of this? Also I replaced the relay (part #R645) on the driver's side firewall but it didn't fix the problem so I hardwired a toggle switch into the circuit bypassing the relay altogether and just turn it on when it approaches the 220 deg. line on the temp. gauge. I do not have A/C but do I still have the fan control switch between plugs 6 & 8 that may need replacing? Thanks for anyone with advice.

 

[quote=celticages]I have the same problem with my single cooling fan not coming on automatically. I brought it to a garage who suggested the ECM's programming was fooled with and no longer controls the fan...anyone heard of this? Also I replaced the relay (part #R645) on the driver's side firewall but it didn't fix the problem so I hardwired a toggle switch into the circuit bypassing the relay altogether and just turn it on when it approaches the 220 deg. line on the temp. gauge. I do not have A/C but do I still have the fan control switch between plugs 6 & 8 that may need replacing? Thanks for anyone with advice.[/quotoe}

i cant find the connector anywhere...stupid manufacturer part....of course they arent open today. .....ya from what everyone has told me i bet thats it. Its not easy to get too. U have to jack the car up and its right their betweem the spark plugs. its a 22mm if its still the original. Any1 parting a car out and have the connector?????????

 

It is the same plug as the knock sensor and availible at most parts stores.

 

really thats odd...i went to three different auto stores and they all told me it was a delearship part for sure. I brought it with me and none of the people i talked to had a clue, they all said they didnt have anything like that....not even something general that could work in its place.

 

They just don't want to look. I worked in a parts store for over a year and I know they can get it. The Murray part number is 37230. These are availible at O'Reilly's.

GM part number 12102621 List price is $17.71
AC Delco Number PT308

 

thanks ill pick that up this week....ive been reading alot about this problem, so i think i understand everything. But i am curious about 1 thing. If the fan switch operates the secondary fan, then replacing it will have no effect on the primary right? i know if i unplug the temp sensor on the front of the motor than the primary will turn on so it works....i checked the relays(with the one on the passenger side thats causes the blowers in the car to go on and they all worked, but is their anyway i could be missing something or i am not getting something. sorry for all the ???'s but i am new to this ...but i neva forget so i will be an expert w/ all the info i've gathered once i figure this out.

 

The computer is supposed to turn the fan on at 220 and off at 205(I think). I may not be exact on the temps, but it is pretty hot. I had my original TPI in my Formula running 170 year round with an aftermarket fan switch and a 180 thermostat. If your car is an automatic the engine needs to reach a certain temp for torque converter lockup. The fan switch for an 87 Grand National is set to turn the secondary fan on at a cooler temp and it is a direct swap in your car. The reason I know this is because I have had all these problems.

 

hey i picked up that part this morning be4 i went to work at some mom and pop auto store(a hole in the wall place). They reassured me that i could've got this part anywhere if they were willing to look for it. Its a stocked item...thanks for the help.

I also talked to a buddy of mine in Mass and he said that because of the way they ground the fans that if there was something wrong w/ the wiring on the switch then it could cause both fans not to work....well i guess ill find out during the week when i get the chance to reconnect the wiring to the switch. Ill keep u update bingo.

 

Keep me posted. I hope we both learn something useful.

 

aight so i replaced the fan switch and i thought the primary fan didnt work still but i let it get real hot and it turned on at a lik 240 basically right be4 it got to the red. It stayed on till it cooled it too 220 just about. The secondary still doesnt turn on but i think it must have to do with the fact that my AC doesnt work at all. From what i've read it turns on when the AC turns on correct(when its clutch engages)????? i tried just putting the blower on but that did no good. Could that AC relay on the passenger side let the blowers in the car come on, but still be messed up?????

i will just replace the relay if its a possibility and not to much money

 

So i'm geussing your next step is a lower degree thermostat? I have been reading along because i have the same problem with a single fan but i have replaced almost everything and mine wont come on.

 

ya i am def gonna replace the thermostat and make it a 160 but i figure if i can get the other fan working when the AC comes on then i can just run the AC if its running hot......thats why i am tryin to figure out if the AC clutch must engage for the secondary fan to go on. If it does i am gonna wait and get my ac fixed. If not then i still have a problem....thats why i was asking about the AC relay. although the AC doesnt work the fans will blow in the car, if u unplug the relay they stop so i didnt know if the relay could effect more than the blowers...if it can i prob will replace that relay...

dingo what do u think???

 

The ground for the fans is usually on the radiator support behind the battery in case you are wondering. That relay on the A/C box is only used for the blower motor when it is on the highest setting. You can remove it and you will notice your blower doesn't work on high. I drove my car for a month without this relay. My fuel pump relay went out and I swapped them until I could get a new one. That relay didn't affect my cars temp. The A/C clutch does not have to engage. The sensor on the hard line by the exhaust manifold has to see a pressure change and it gounds the relay turning on the fan. The wire it grounds is actually the same wire going to the fan switch.

 

I apologize for any intrusion but I've been following along as well and I'm looking for the silver bullet to fix this problem. I want to get back to the stock configuration (fan turning on automatically) rather than a manual toggle switch (see my post above). The question is...even though I don't have A/C, is there another relay besides the one on the driver's side firewall that may need replacing for it (single fan) to come on? Thanks.

 

I am pretty sure that the AC relay does not have anything to do with the fans on the inside of the car coming on that blow air through the vents. It turns the cooling fan on when the AC comes on.
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Seems that the switch in the passenger side head controls the fan, if that is bad then it may not come on if the relays are good.

 

A lower temp thermostat will not turn your fan on earlier. The switch in the head opens at a certain temp. You can use a switch out of another GM car that comes on at a lower temp if you want it to come on earlier. I remember a while back someone posted that the switch from a Grand National comes on earlier and is a direct swap. Do a search here and you should be able to find it.

 

a buddy of mine told me this morning that the a/c pressure switch can cause the secondary fan not to work(he believes the secondary fan is primarily for AC use; i know a few peeps who have to always run their ac to keep their cars at a normal temp, so this may be my secondary fan problem). I dont have AC or any pressure in the lines so i am going to try jumping it with a wire later this week. I dont know if it would effect a single fan set up. I will try it and keep everyone updated................

 

Ok...I apologize for my ignorance but there is a switch inside my passenger side head? The valve head? I know this question must sound ridiculous to most gearheads but I never heard of a switch being inside a head before. I don't doubt you guys but I am trying to educate myself. Thanks.

 

It is not a switch in the sense that you may be thinking. It is not something you click on oor off. What it is is a sensor, which once it reaces a certain temp it ( the inner wiring) opens up making a complete circuit basicly. My description may not be perfect but I think is more or less on the point. When it completes this circuit it alows power to go to the cooling fans. This switch is easiest seen from the bottom of the car, looking between the #8 and #6 cylinder in the side of the head. If you need any more help feel free to PM me with any questions.

 

The only thing you were wrong about is that the switch does not control the power, it controls the ground. At a specific temperature the circuit is completed thus grounding the circuit. This provides a ground for the fan relay causing it to engage. To keep the fan running everytime the ignition is on, one must simply ground the wire to the fan switch. There are two possible ground paths provided for the secondary fan. One is the aforementioned fan switch, the other is the A/C pressure switch located on the hardline down near the base of the strut tower. Unplugging the pressure switch and jumping the two terminals with a paper clip will complete the circuit ground and allow the fan to run when the ignition switch is in the on position. When my fans switch was broken I used this method to keep my car from running hot.

 

Yeah my bad, you are correct it completes the ground. Thanks.

 

ok 87 lg4,ive searched diagrams high and low and cant seem to find it..i know the fan relay is oon the firewall..but is there a second relay for the fan,i have the stock single fan,auto tranny.theres a factory relay,same shape as fire wall one,mounted on the passenger side of the radiator/core support..whats that relay for?i cant find anythign in the manual for it..please..

 

I hope this help

 

Yes...what is that relay on the radiator core for? If for fan...why two relays? Is it the same part # as the firewall relay? Thanks....

 

i found my answer.its the fast idle solenoid relay for the ac on a carb car