radiator fans do not come on at over heat temperature

**garraper** · 10-25-2013

i had a independent gm dealer (one who lost there franchise) diagnose ,,saying the fans would run if he bumped them to make them start running..does this sound like the problem? i changed the cooling sensore and the thermostat ( 180 ) the fans will both run when jumped with battery 12 volts. help..

**darkhorizon** · 10-25-2013

My GTP's fans are currently broken.. I cant command them on with HPtuners or the a/c request, or the defrost setting. Im expecting it to be a PCM failure but havent swapped out the pcm yet.

**Fivefingerdeathpunch** · 10-25-2013

Could be a relay issue, maybe?

**garraper** · 10-25-2013

relays where checked and are working..the gm tech said the brain was telling them to come on..but fan needed to be bumped to start..i ordered 2, 12 inch fans from amazon.. i have to replace the radiator also,which i bought from JC Whitney

**02NavyBlue** · 10-25-2013

Why did you order new fans if you said yours came on when jumped? Check all fuses first. If you confirmed that the relay was working, make sure that the wires leading to the power distribution box are hooked up and getting voltage. If so, check for power at the connector to the fans. If you get power there, but not to the fans, the contacts could be dirty. If you don't get power to the fans but did at the relay, check the wires and the ground. That may be the issue.

You didn't mention what car you're driving, but assuming its a grand prix, and a 97-03 here's a wiring diagram.

Check ground 117 and power to both fans, just keep tracking power til you lose it, then find out why.(assuming the relays do click but no fans)

**Timing** · 10-25-2013

This^

**garraper** · 10-25-2013

i will check grounds tomorrow,also pop the tops of all 3 relays to see if heavy contacts will activate when pushed in by hand..

**02NavyBlue** · 10-25-2013

You could always swipe a fine grit sandpaper in the contacts in case they're not clean.

**garraper** · 10-26-2013

i was side tracked today..monday will replace radiator...

**Scottydoggs** · 10-26-2013

why change the radiator if the fans are not coming on?

you can also wire a switch to the fans and turn them on and off manually till you figure the problem out.

if you do wire a switch, use a relay or one for each fan even.

**coolone** · 10-27-2013

Shot gunning parts at a problem via process of elimination is costly and not the correct way to fix it.

1. If you're unsure of your ability to tackle a problem or lack the fortitude to see it thru, I suggest you let someone else fix it.

2. If you come to a forum such as this in an attempt to fix it yourself and ask questions, at least give what is suggested a try, you may find that people know what they're talking about.

3. If neither of the above two items work for you, then why bother, just get a new car!

: )

It has been laid out here, ways to approach and potentially fix the issue. But maybe you need to understand what will cause the fans to turn on or off to begin with.

First, the thermostat will not help the fans turn on or off. It just opens and allows coolant to flow upon reaching a certain temperature. Your engine has a temperature sensor which tells the computer how hot/cool it is. When reaching a certain temperature the computer will tell the fans via relay to turn on or off. So... Seeing as the fans are electric and not belt driven, you need to trace the circuit as mentioned. You can trace it from the relay to the fan and check for continuity without voltage to ensure there's no break in the wiring, grounds as well. Then you can check when the engine is up to temp for the fans to be on and see if there is voltage as it should be. You could cheat and swap the fan relay with another and see if it is the relay malfunctioning, or jump it out as you said. If the wiring is good, the relay is good, the fans are good, then I would agree the PCM is potentially an issue. Lastly, you could just bypass fixing it at all and install a switch as mentioned and control the fans manually...

but go ahead, change the radiator... Seems you've got lots of free time and money on your hands!

good luck! Don't forget to let us now how it all turns out...

**garraper** · 10-28-2013

coolone,thanks for your input. the radiator is leaking..i did not want to change it untill the fan problem was solved..so money and time are not the issue..i also did a manual switch on my VW 1.6 diesel dasher,that i still own. the VW gets 48 mpg with no computer,the gt gets???? with all the great technology..

**garraper** · 11-04-2013

the new radiator is in also had to make trans cooler lines..fans still not coming on..i looked at the hptuner site that said it will test the fans to come on, in the down loaded program they used..is there any one in the jersey shore area that does this flashing????? thanks..

**garraper** · 11-08-2013

the car is a 1999 gt..on the other forums,the info was very help
full on getting to the cpm turning on the fans..also hptuner info was ok..i am still trying to get some one in the area to that knows how to reprogram the cpm, any one?

**Scottydoggs** · 11-08-2013

theres a guy on the board here

Nighthwk12 hes from NJ some what north of you but iirc hes got a tuner, not sure what years hes got unlocked but its worth a PM to him.

**garraper** · 11-09-2013

Thanks Scottydoggs, i had the gt out today on the parkway and the new rad works great,except for small stuff,other than my fan problem..I will be running to the polar bear tour run tomorrow riding my BMW r1100r MC,so will try to touch bass with nighthwk12 later in the week thanks again Gary

**darkhorizon** · 11-11-2013

turning on the defroster heat setting will make the fans come on... No HPT required.

**garraper** · 11-13-2013

darkhorizon,thanks for the tip. # 1, the dash fan switch only runs on full .# 2, the ac is not charged,which makes the rad fans run and they do not. your suggestion also doesn't make them turn on.. i haven't been able to work on the beast for awhile,but its been cold, and the new rad makes it run no higher than about 190 according to the gauge.. it is a fun car.. i still would like a good tech, to give $ me some help that has a hpt $ ..