Turbo Buick Forums banner
1 - 20 of 21 Posts

·
Registered
Joined
·
176 Posts
Discussion Starter · #1 ·
The coolant fan on my 87 GN dosen't work even with the a/c turned on! Heres what I've done/checked so far....

With 12 volts applied directly to the fan it works okay (hi speed). However, it won't work any other time as it's suppose to! There is 12v at the relays, but NONE at the fan plug (male) receptacle. There are NO fuses blown at the fuse panel/box.

Where should I look next??

Thanks,
HOW
 

·
Premium Member
Joined
·
43,735 Posts
section on fan troubleshooting on my site under troubleshooting.
 

·
Older--but Getting Wiser
Joined
·
2,250 Posts
What Steve said!
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #4 ·
Steve Wood said:
section on fan troubleshooting on my site under troubleshooting.

Steve

Which connector at the a/c compressor you talking about, the round connector at the back side of the compressor or the female spade just behind the pulley? The spade has the only green wire that I can determine. The round connector has 2 "dark" wires but they aren't green, I removed the wrapping back from the plug 3-4" but still no green. Anyway, the fan won't run period-even after grounding all 4 wires.

However, it will run on high when the coolant fan switch wire is grounded, and other than that the ONLY other way the fan will run is when a direct 12v source is applied at the fan motor?

Gettin' flustered......
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #5 ·
BTW, does the a/c high pressure switch plug receptacle require it be plugged in a certain way..it will plug in either way??
 

·
Premium Member
Joined
·
43,735 Posts
The ac switch has two wires...one is green/yellow and it triggers the low speed fan when grounded. The other wire is green and it triggers the high speed fan when grounded. I don't recall the shape of the connector.

Now, the fan should come on low speed when the ecm tells it to...that depends upon what is programmed into the chip. Factory chips were set a a high temp while most aftermarket chips are closer to 160 degs.

It is reading the temp from the ecm which is getting it from the coolant sensor on the front of the the intake by the thermostat.

I assume your scantool is showing proper coolant temps? If it is not, then the fan won't come on unless you turn the ac on.

Now, we know the high side is working if you ground the green/yellow wire on top of the manifold. Find the right connector on the ac, or just look at the relays and find the green wire and ground it....does the fan run? (Edited the wire colors as I had them backwards)

If it does then it would tell you that the fan system is working okay, and that the problem is probably a bad sensor or switch.

Did I fluster you more :)
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #7 ·
NO Steve you are being a tremendous help, it's just my nature to stay flustered most of the time.

...now, I'll add more the my confusion!

Back earlier this year the fan motor went bad and I replaced it with another good stocker. I made a modification to the wiring by connecting both wires at either end of the resistor together. The fan would come on and run on high anytime the ac was turned on, or it would turn on whenever the ecm sensed whatever temp was set at, also on high speed.

If either one of the 3 relays is bad does/will it have an affect on the fan operation? I replaced the low and high relays with known good ones so I don't think its one of them.

Relay fuse 5 amp is okay.

Can the fan be wired up to where it will run backwards?
 

·
Premium Member
Joined
·
43,735 Posts
yes, there are two smaller relays on the fender. One controls the low speed and one controls the high speed aspect.

Lot's of us have jumped the resistor to get high speed and that is okay...might make the motor last longer. I really don't know what happens if you wire the motor backwards...I assume that is not the problem because I understood it ran okay when you grounded the dark green wire at the coolant switch.

As you asked, why don't you swap the two small relays. If it now comes on when the ecm reaches the proper temp, then you know you have a bad relay. :)
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #9 ·
If the delay relay is bad would this keep the coolant fan from running at all?
 

·
Premium Member
Joined
·
43,735 Posts
don't see how..the fans will function well without it plugged in at all...Pull it and see if there is a change :)
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #11 ·
Steve,

At the wiring diagram at your website concerning the coolant fan, is the "Coolant Fan" wires A and B the ones going to either end of the resistor, making the black wire "C" the voltage source??
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #12 ·
When the 2 wires at either end of the resistor is tied together are they re-attached somewhere else??

Sorry for all the questions, and I very much appreciate your help.
 

·
Premium Member
Joined
·
43,735 Posts
A is the black/red wire coming from the low speed relay. It should be hot when the ecm sees the programmed temperature in the chip. Even tho' you have jumped the resistor, this wire still turns the fan on from the ecm.

B is the black/pink wire coming from the high speed relay. It is hot when you ground the green/yellow wire.

C is the ground wire. It often gets hot and melts the connector which causes a problem. However, this is not your problem as you said it ran when you grounded the green/yellow wire to the coolant switch on top the intake.


Now! You are jumping around. Take a deep breath! :D

Did you ground the green wire from the low speed relay? I may have screwed up and said green/yellow, but, I meant green? Did the fan run?

If you have not done that yet, first swap the two small relays and see if the fan runs when the car comes up to temperature.
 

·
Premium Member
Joined
·
43,735 Posts
HellOnWheels said:
When the 2 wires at either end of the resistor is tied together are they re-attached somewhere else??

Sorry for all the questions, and I very much appreciate your help.
The black/red wire goes to one end of the resistor. The resistor drops the voltage and makes the fan run slower. You leave the wires on the resistor connected as originally wired and add a new wire that runs between the the connectors on each end of the resistor. If you disconnected the black/red wire, you can have no ecm control to the fan.
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #15 ·
Steve Wood said:
The black/red wire goes to one end of the resistor. The resistor drops the voltage and makes the fan run slower. You leave the wires on the resistor connected as originally wired and add a new wire that runs between the the connectors on each end of the resistor. If you disconnected the black/red wire, you can have no ecm control to the fan.

Steve, the resistor has been completely out of the picture for some time now and up until this go round the fan has worked fine, or at least I "think" it has?

I've ran out of daylight but will be working on it first thing am.

Man I sure appreciate your help.
 

·
Premium Member
Joined
·
43,735 Posts
All three wires that originally connected to the resistor should be tied together. I believe there were two at one end, and one at the other. You will get it going. :)
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #17 ·
Should the coolant fan come on when the ign is turned to run and the ac is turned on?? (Engine is cold, engine NOT running)

Thanks,
 

·
Premium Member
Joined
·
43,735 Posts
no
 

·
Registered
Joined
·
176 Posts
Discussion Starter · #19 ·
Steve Wood said:
All three wires that originally connected to the resistor should be tied together. I believe there were two at one end, and one at the other. You will get it going. :)

Steve,

You did it!!!!, you led me to the problem!!!! with the above "3" wire comment, I had 2 of the 3 wires tied together and couldn't see the other as it was hid by the i/c shroud, once that baby was hooked up the fan came on as suppose to.

Thanks for all you help, I appreciate your time and patience(sp) don't think I would have ever found the problem without your help. Hope I can return the favor sometime.
 

·
Premium Member
Joined
·
43,735 Posts
cheap fixes are the best! Glad you are back in business! :usa: :cheers:
 
1 - 20 of 21 Posts
Top