95 chevy lumina fans don't work

I have a 95 chevy lumina and the fans are not working, I put new relays in and a water pump and i bleed the system and put a new Coolant Temperature Sensor, and Thermostat, still the fans don't come on. someone told me it might be the Pressure In Compressor Switch but i look all over for it and i can't find it can someone help me please?????

The fan(s) will only run when engine temp calls for it, or the A/C compressor is engaged...

how long are you letting it run? does it overheat?

The fans won't run much, if at all, in colder weather...

And "W" car fans "WAIT" on head pressure to rise to 175 before they come on-- so just turning on the a/c does not guarentee fan operation either--- engine temp need to be about 227 degf to request the fans as well--- used to be they would come on when you jumper your ALDL to check for SES codes--- but I am spoiled by my Tech I-- which I can command fans on with to test them---

Why do you think you have a problem?? boil over? or just a higher than normal temp gage???

I just put some head gaskets on it and its overheating.

Are the radiator and upper hose hot to the touch when it starts going over to hot?

You try letting it run, select full heat on the dash, with the bleeders and cap open at operating temp? There can be some real stubborn air after a complete empty...

Also if you have a compression leak you'll probably see endless steady air bubbles from the bleeders...

Also there are two CTS, you replaced the one for the ECM, yes? The other is for the guage..

yeah the radiator is hot and the upper hose, on the heat on the dash gets hot but not like it should, and I did replaced both CTS and the ECM. But the low coolant light does come on too

yeah the radiator is hot and the upper hose, on the heat on the dash gets hot but not like it should, and I did replaced both CTS and the ECM. But the low coolant light does come on too

unplug the fans connector and place 12v across input to fan... does fan run..... check all wiring to fans and grounds....in winter the fans normally will not come on unless the vehicle idling with hood closed for a long time....I would suspect that as stated air in coolant is interfering with water pump operation and by leaving fill cap off with vehicle at operating temp this will help get the air out..... also look for coolant purge valve at thermostat goose neck and open to release air.....

unplug the fans connector and place 12v across input to fan... does fan run..... check all wiring to fans and grounds.....

good point...lotta times after major surgery a ground wire taken off hides and doesn't get put back on....

ok I try the 12v across input to fan and the fans work but when I unhook the Coolant Temperature Sensor and start the car they come on and the car runs ten times better but I just bought that temperature sensor not to long ago so I know its not bad and I also bleed the system agine with the fill cap off I think its air free.

ok I try the 12v across input to fan and the fans work but when I unhook the Coolant Temperature Sensor and start the car they come on and the car runs ten times better but I just bought that temperature sensor not to long ago so I know its not bad and I also bleed the system agine with the fill cap off I think its air free.

you must replace the ECT this is mounted at the thermostat this info then goes to the computer and not the dash guage.....Engine Coolant Temp...........computer will then put fans on when coolant at thermostat is about 230deg. f

ok I try the 12v across input to fan and the fans work but when I unhook the Coolant Temperature Sensor and start the car they come on and the car runs ten times better but I just bought that temperature sensor not to long ago so I know its not bad and I also bleed the system agine with the fill cap off I think its air free.

I was given the wrong CTS from a parts store once...made the car run rough as hell (ECM was reading it as temp at bottom limit, full rich)

Never assume the part is not the problem...especially if you just installed it and then had problems.

my favorite saying is "If I had a nickel for every customer who ever said "It can't be [insert part name], because I just had it replaced.."

That was the first thing I checked, and 90% of the time, that was the problem...:grinyes:

I was given the wrong CTS from a parts store once...made the car run rough as hell (ECM was reading it as temp at bottom limit, full rich)

Never assume the part is not the problem...especially if you just installed it and then had problems.

my favorite saying is "If I had a nickel for every customer who ever said "It can't be [insert part name], because I just had it replaced.."

That was the first thing I checked, and 90% of the time, that was the problem...:grinyes:

this is very possible that he was given a defective sensor but i believe is is unaware that one sensor goes to gauge and the other at thermostat goes to computer that drives the fans....

ok I bleed the system for along time and then i let the car set and Idle for along time and when it started to overheat the fans kick on. So is that normal for it to overheat when set idle for a long time?

what is happening when it starts to overheat? does the coolant boil ? is it because of the reading of the dash temp gauge position.....lets say its boiling but the dash gauge is not max and you have the coolant cap securely on so that 14psi can build up in the radiator...then i would say that the cap is no good because coolant should not boil at 14psi at 230deg f...



the higher the pressure the higher the temp for water to boil in Boston water boils at 212 In denver its 187........

ok I bleed the system for along time and then i let the car set and Idle for along time and when it started to overheat the fans kick on. So is that normal for it to overheat when set idle for a long time?

My '97's fans turn on when the gauge is about 3/4 of the way up the scale, but these gauges are pretty meaningless...every one reads different.

The question is, did it bring it back down quickly once the fans ran, or did it just sit at that temp or climb higher?

Idling, it should bring it back down to normal within 20-30 seconds or so...

I guess the other question we haven't aksed yet is what does it do when you drive it?

As long as you're moving, the fans are not needed...if it still goes hot when moving down the road, the fans have nothing to do with it...

when its starts to overheat the light will come on and the fan will kick on and the gauge will back down in between the normal and the red line.

when its starts to overheat the light will come on and the fan will kick on and the gauge will back down in between the normal and the red line.


I then would like to know what temperature sensor did you replace ? ... the sensor at thermostat is the one that tells ecm to turn on fans.....that is the sensor that has to be bad....did you replace sensor at thermostat? when it gets to the overheat condition is the coolant boiling.. is the recover tank above full hot .....from cold to normal temp the recovery bottle should rise from cold level mark to hot level mark does the coolant rise like this? if not replace the coolant cap....

IF THE VEHICLE IS NOT MOVING THE FANS WILL COME ON EVENTUALLY , BUT NOT WHEN YOU GET A WARNING LIGHT THAT INDICATES OVERHEATING....these sensors are resistors remove both sensors measure resistance both should be the same resistance..... then place in boiling water again both should read the same resistance......can you do that.....?

when its starts to overheat the light will come on and the fan will kick on and the gauge will back down in between the normal and the red line.



before starting engine the resistance of the sensors ect and cts are at 40deg f resistance of 7300 ohms , then when vehicle is at normal temp of 195deg f the resistance should be 240ohms...they don't have to be removed just measure in place with connector removed....now if at 195deg the sensor reads higher ohms than this amount , then the ecm will think the the temp is lower...as the higher the resistance the lower the temp...this I believe is why fans come on too late or does it ?

I think my ECT might be bad but I have some questions. Ok my primary fan seems to not be coming on it gets hotter then normal now when I stop. It will turn on tho if I engage the ac compressor I need to check it again though. My coolant is full also. Anyway if the ect was bad wouldnt that keep the motor from going into closed loop also and throw a code or is it possible it just throwing false info the the ecu and not throwing a code?? What other coolant sensors does the car have?

Thanks,
John

I think my ECT might be bad but I have some questions. Ok my primary fan seems to not be coming on it gets hotter then normal now when I stop. It will turn on tho if I engage the ac compressor I need to check it again though. My coolant is full also. Anyway if the ect was bad wouldnt that keep the motor from going into closed loop also and throw a code or is it possible it just throwing false info the the ecu and not throwing a code?? What other coolant sensors does the car have?

Thanks,
John



one sensor ECT is near the thermostat this is the fan computer sensor, I don't know were your dash temp sensor is located you will have to find out..... anyway both should read the same resistance ... if not ....then at certain temps you will get a specific resistance , ,, if incorrect fans may not come on correctly....as well as other problems like if computer thinks ....... its -40deg out engine may not start correctly.....if the connector or wiring is bad then it will throw a code if it reads the wrong temp no code...

one sensor ECT is near the thermostat this is the fan computer sensor, I don't know were your dash temp sensor is located you will have to find out..... anyway both should read the same resistance ... if not ....then at certain temps you will get a specific resistance , ,, if incorrect fans may not come on correctly....as well as other problems like if computer thinks ....... its -40deg out engine may not start correctly.....if the connector or wiring is bad then it will throw a code if it reads the wrong temp no code...

Cool thanks a lot.