Cooling Fan Diagnostics
Thread Starter
Teching In
Joined: Sep 2008
Posts: 12
Likes: 0
Cooling Fan Diagnostics I cant get my coolant fans to run. So far I have checked all the fuses, relays, tried unplugging the ect, and tried to put the car into service enable mode by jumping the pins in the dlc. Nothing makes them turn on. Where should I go from here? Thanks guys this is annoying. The car is a 1997 btw.
TECH Fanatic
Joined: Jan 2004
Posts: 1,157
Likes: 1
From: Kingfisher Oklahoma
First unplug the MAf and then start it , it should kick on the fans immediately, if they dont then you have a component bad. The 93 was the last year you could jump the ALDL and get the codes and put it into diag mode. The 97 is OBD2.
Thread Starter
Teching In
Joined: Sep 2008
Posts: 12
Likes: 0
Ok so after doing some diagnostics with my power probe here is what I found out. The fans come on when the ses light is on. They fans come on when the a/c is on. The high speed function comes on at about 3/4 temp on the gauge which I assume is 235F which is normal. For some reason the low speed function isnt working which is at like 225f I believe. There is no reason the gauge should ever go that high correct? I pulled the coolant fan relay #1 and tried sending power down the lines with no luck, This system is wild. Should I assume its pcm problems at this point?
If you tried to hot jump the fan at the relay and it did not come on then I'd say you need to look at the grounds, power wires leading to the fan or the fan motor it's self is bad. Make sure you tried to jump the correct sockets where the relay goes. 2 are for the PCM and 2 are for the fan +power.
Thread Starter
Teching In
Joined: Sep 2008
Posts: 12
Likes: 0
The car is a 6 speed. When I pull the relay I have 2 hot pins and 2 that I can send power down. The motors come on high speed , so doesnt that rule out the motors? Plus, would both low speeds go bad at once? All the wiring in this car is untouched and clean.
Trending Topics
If I remember right one is low speed only and the other is either high only or low and high. Which fan (drivers or passenger) wont turn on low? never mind I see neither
Last edited by jaycenk; May 4, 2012 at 10:45 AM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Same things happening with my fan. Fan 1 will kick in for ac ses and high. Temp that's it. But if I pull the relay then fan 2 will take over. How ever im not able to get ether of them to work at the low temp mark. My cars a 94 z28 m6
Thread Starter
Teching In
Joined: Sep 2008
Posts: 12
Likes: 0
At low speed it should be both fans, I know that much. I jump 12 volts down both pins that have no power not knowing which one is the right one. When I jump this 12 volts though dont I need to also make my own ground since the pcm supplies thatI believe?
no. Ok you should have power with key off at one pin. If you look at the under side of the relay all of the prongs are marked with a number. Where pin 30 goes into the fuse block you should have 12 volts all the time unless the batt is disconnected. Pin 30 is the supplied power source from the positive distribution block on the passenger fender next to the batt. When the relay is activated by the pcm it passes the power from pin 30 to pin 87. Not 87A but 87. One pin is not used from the relay to the fuse block. If you dont have power at pin 30 then that's at least one of your problem.
Thread Starter
Teching In
Joined: Sep 2008
Posts: 12
Likes: 0
ok what if I go to the dark green wire at c100 with my power probe and ground it? Should the fans then come on if everything else checks out fine? Thats assuming I have power at pin 30 which I will test tonight.
It's been a while since I was inside the fuse box but if that's the ground to the PCM then yes but It will throw a CEL light if you do that because the relay's trigger contains resistance in it that the pcm looks for. The PCM also knows when it's supposed to be on and will throw a CEL if it turns on before the programed temp. I went though all this when I was tring to wire up my fans manual before I had a tune and the only way I managed not to end up with a CEL was to cut the green and the other small wire for the trigger and wire in a resistor that matched the relays resistance. I dont remember what it was since it was 4 years ago and I have since wired it back and had a tune done to turn them on at lower temps.
That said I dont like to manipulate stuff when the PCM is powered. I would say just put a meter on it and let it run up to temp and see if the PCM makes the connection for you to get a reading on the volt meter.
That said I dont like to manipulate stuff when the PCM is powered. I would say just put a meter on it and let it run up to temp and see if the PCM makes the connection for you to get a reading on the volt meter.
