The fan is NOT running at low speed with A\C on . It will not run period. I have a new fan sitting in my shop. Should i try to install it ?

 

I hooked up new fan, just for a test .Started the car with A\C on . The NEW fan and It would try to start turning, but then stop. I mean it would just start to move about a 1/4" then stop . That happened 2 times . What is it ? Grounds are good . Wiring is good . I dont get it !

 

Ok, there is one thing I can think of - it's wiring. Wait, let me go check something, be right back..

 

Let's explain to you how the system works, ok? You have to fix this pretty much on your own (since we are not there) and the first step in fixing it is understanding how it WORKS. From a post in another thread where I was trying to help a guy, I added the italics for this thread:

It works like this:
FCM = Fan Control Module
PTCM = Power Train Control Module

On the FCM, there are two HEAVY wires that supply power to it, one is, of course, 12 volts, and one is ground. There are two HEAVY output wires, too - they go to the fan motor and are power and ground.

There is one single, small wire, it is GY (Gray) and is the two-way data link from the PTCM to the FCM.
There is another small wire, it is PK/RD (pink - red) and is the ignition switch input to the module.

Ok......

There is a single wire running from the PTCM to the FCM. This wire has 12 volts on it, the PTCM pulls this wire to ground in a series of pulses, the WIDER the pulses, the faster the FCM makes the fan run. (It does this by sending pulses of 12 volts to the fan motor, your meter will show 4 to 12 volts, but that's because your meter is averaging the pulses - DC motors are not usually run on low voltage for low speed, they are run on NORMAL voltage that is pulsed to get the right speed). Periodically, the FCM also pulls the line to ground - this tells the PTCM that the FCM is still working.

The PTCM turns the light on if it does not see the pulses coming back from the FCM.

Also, if the FCM does not see the pulses from the PTCM, it assumes something is wrong (which is the case) and that the engine's temperature is unknown (which is also true) so the FCM turns the fan on all the way. If the light is on and the fan is running full speed, there is a communication breakdown between the modules.

If the light is on and the fan is not working, then the big fuse to the FCM isprobably blown OR the FCM is bad. (I do not think the FCM can sense a bad fan motor.)

You can always unplug the fan motor from the FCM, the connector is clipped to the radiator support on the driver's side - use wires with the end stripped off and see if you can jumper the fan motor directly to the battery. If the motor turns, the FCM is bad. If the motor does NOT turn, the motor is bad.

Using a meter:
Make sure you have 12 volts on that PK/RD wire.
Make sure you have 12 volts on the heavy lead going into the FCM (and I think you do, or you'd have a radiator light).
Make sure your heavy ground input is ok (But, again, if it wasn't, I'd suspect you'd have a light on)

It SOUNDS like the 12 volts is not making it to the fan motor harness. Ground your meter well and probe the 12 side to the fan AND the ground side. YOu should see pulses that average on a Digital meter to something about 4 volts on the hot lead going to the fan and less than .1 volts on the round lead coming back.

As an acid test you can CUT the Gray wire (do this so that you have enough wire to splice it back together). By cutting this wire, you will cause the FCM and PTCM to loose contact and:

1) The PTCM will go into alarm and light the radiator light - telling you that you have a cooling system problem.
2) The FCM will go into emergency mode, because it has lost contact with the PTCM - and will fire the fan off at 100% full speed. This means the voltage to the fan will be 12 volts, up to 14 if the engine is running!

NOW you can find your problem. I STRONGLY suspect there is a corroded, loose or bad connection between the fan motor and the FCM. Again, if the FCM does not have the power it needs, it won't likely be able to pulse the PTCM and the PTCM will light the light - and you say the radiator light is not on!

I"m thinking cutting that wire will tell you more than substituting parts. But I DO NOT believe you have two bad fan motors OR two bad FCMs.... gottta be wiring. If you turn the A/C on, the fan runs slow, about 150 rpm or mabye 200 rpm. If that isn't happening, and the radiator light is not on, gotta be a bad motor or wiring from FCM to Motor.

Unless I am missing something. But even if the temperature sensor is lying about engine temp, turning the A/C on HAS TO RUN THE FAN. THere is no way around this.

 

Wait a minute.... better make SURE you have 12 volts on the PK/Rd wire with the key on. This is one of the two SMALL wires going into the FCM.
I guess I already said that - but make sure it's there.

The Gray wire will have, essentially, 12 volts on it as well.


MAN, this should not be this hard....

 

I Have 12v on the PK/RD wire withe key on and A/C on
1.0v on gray wire with key and A/C on

Large wires going into the FCM
BLK-4.7v
BLK -13.0v
OR-0
OR -0
when i started the car with A/c on I measured again
PK/RD- 4.5v
GRAY 4.5v as i was removing insulating wrap on gray wire the fan kicked on at low speed !!! yipppeee

So that tells me that you were CORRECT !Bad connection or wiring at harness .Right ?

 

Fan is running now Still have 1.0v on gray wire with key on . 5v with engine running. 12 v on pk/rd wire engine on and key on.
Any way i unplugged harness to FCM and fan , put a small amount of dielectric grease on terminals.

 

WHY WAS IT, that when I came back to the computer I had a funny feeling you'd tell me it's running???

Yea, it's bad connections - and we know now that it CAN run right if it wants to, so no damage to the modules...

I Have 12v on the PK/RD wire withe key on and A/C on
1.0v on gray wire with key and A/C on

Large wires going into the FCM
BLK-4.7v
BLK -13.0v
OR-0
OR -0
when i started the car with A/c on I measured again
PK/RD- 4.5v
GRAY 4.5v as i was removing insulating wrap on gray wire the fan kicked on at low speed !!! yipppeee

The first black at 4.7 is going to the fan. The second one, comes from the battery/source. THese check out ok - about 4-5 volts is what you get with a not-hot-yet engine but WITH A/C on. TUrn the A/C off and that lead will go to 0.

Pk/Rd should be either 0 (key off) or 11-14 volts with key on and running. This is a raw ignition switch feed to power the module.

The Gray wire will show anything, as it's pulse modulated.

You might test the Fan Module you bought - if it checks ok, and I"m sure it does, you can advertise it here in our parts-for-sale area. SOMEONE is gonna want it eventually.

===================

Beware that SOMEWHERE a pin was corroded or something. THis can be the mating contacts that you lubed OR it can be the contact between the strands of the wire and the crimp terminal at the connector! It could even be at the other end (at the ignition distribution block or the PTCM - but I doubt it since you started to wiggle and probe wires and it started working - likely it's right there at the fan module.)

 

Pizza Guy- Thank you so much . Man u educated me Big time . I probably spent $300 ON STUFF I DIDNT need.

 

Look at other threads - some people have spent $2100 on parts they didn't need!

And your parts can be used later or sold! Fan motors DO fail kinda often, we went thru a spat of them about a year ago on this forum, people were showing up, seems like, every week looking for fan motor assemblies....

Im glad I could help - it's hard troubleshooting over the internet - I'm glad I'm not a telephone tech support guy, that would be a HARD job!

 

Since i have You . The car needs some brake pads. I hear ceramic is the best .{DUST!} Can i just get them at Auto Zone or do i need to order on line some where ?

 

PERSONALLY, I like Hawk HPS pads, I have them on the front. They DO NOT FADE in a panic stop from 80mph (don't ask how I know this...) and their dust is about 1/4 of OEM's.

My car stops a LOT better now!

I got mine online, I THINK from TireRack - but I know I googled them and went to where the price was lowest.
Pretty sure it was TireRack.