abilak

Ok, so if I test the green wire toward the relay and it gets a reading then it is getting grounded out, right? Meaning that it is touching some metal somewhere?

As far as the meter goes, if it has a 10K ohm selection on it does that mean that it will not damage the PCM? Here are the specs for my multimeter: Capacity: AC voltage: 200-600V, DC voltage: 2-20-200-600V, DC current: 2mA-20mA-200mA-10A, resistance range: 200-2k-20k-200k-2M-20Mohm

I will post the results later tonight.

abilak

Okay... Tested the dark green wire for ground with the relay in and the relay out and nothing... no continuity. I didn't test it back toward the PCM because I wanted to make sure that my meter wouldn't damage the PCM.. could someone please tell me if it is ok to use? I posted the specs in a message right above this one. Thanks.

shoebox

The impedance of the meter is usually in some printed specs. If it is a modern digital meter (not a real cheapie), it should be ok.

abilak

Sorry I am being so crazy but I don't want to damage my PCM.. here are the specs from my meter... under the ohms section it says 10Mohm.. does this mean it's ok?

Here is the spec sheet:
click here

shoebox

Looks ok to me. It says 10Mohm in the DCV specs.

abilak

Thanks for checking that out for me.. okay later tonight I will check back toward the PCM then... another question...

If the car is off, the ignition is off, and the fans are running (which they still do), if I tap the dark green wire while the C100 clip is connected and test for voltage should I see something if the PCM is malfunctioning and sending.. i guess what my real question is... when the PCM wants to turn on the fans it supplies a ground to the wire coming from the ignition and through the relay, right? so, while the fans are running, and supposed to be running, there is voltage in the dk green wire, right? at all times.. or does the PCM just send a pulse to kick the relay on?

What I am getting at is if the PCM sends voltage to the relay, then stops sending voltage, does the relay switch back to it's original position or does it stay "closed"?

So if the PCM is not sending a "signal" when my car is off then surely one or more of the relays are staying "on" or closed.

shoebox

If you "tap-in" to the drk green wire while the fans are on, you should see a ground, not voltage. The PCM sends a ground on the green and blue wires to activate the relay. No voltage is sent by the PCM to the relay.

When the ground signal is gone, the relay is not supposed to be operated.

abilak

Ok, I just did a few tests and still have questions... someone at work told me that if a wire has voltage in it then you cannot use the OHMS setting to test for ground because it will give a false ground due to the voltage in the wire.. here is what I did.. when the car was off and the fans were NOT running... I tapped into the dk green wire while the C100 clip was fully connected and I saw a ground and also 8volts.. This is normal right.. because voltage is flowing from the ignition through the relay, to the C100 clip, and I am "making" a ground with the meter? right? should there be voltage in this wire while the ignition is off? is that normal?

exactly how should I test this when I get home and the fans are still running? if I pull the C100 clip they shut off.. can I jump the dk green wire to ground to kick on the relay and test it that way.. same with the dk blue??? and if they work and then shut off when I unground them does that mean that the computer is still providing a ground when the car is turned off? how can I absolutely verify this??

someone else told me that maybe when I unplug the C100 clip, while the fans are running and the car is off, the computer senses that I broke the circuit and stops providing a ground.. is this possible and or true? please help this is absolutely driving me crazy and I am really trying to get to the bottom of it!

also -- where is the sensor that the computer uses to sense the coolant/engine temp to decide when to turn the fans on?? is it possible that the sensor is bad and telling the computer that the fans need to be on.. and if that is true.. would the computer ground the circuit when the ignition and car were off?

sorry for all the questions but like I said before I really want to understand whats going on and get to the bottom of this soon!

abilak

Okay, I tested the relays by jumping the dk green and blue wires to ground.. the click on and off perfectly. So, i guess that means that after the car is off the pcm is still providing a ground for the dk green wire (low speed) because the fans are still running... when I pull the C100 clip or the cooling fan #2 relay, the fans kick of and DO NOT turn back on when the relay and/or clip is plugged back in... So if the PCM was providing a ground to the fans while the car was off, and I pull the C100 clip or the fan relay #2, would that make the PCM stop providing ground.. that really seems like what is happening here. any suggestions or more tests that I can do?

shoebox

It is correct that you cannot look for a ground in the presence of voltage.
You should not be seeing voltage on the green or blue wires, though. That is probably what is holding your relays operated. If you can verify that the voltage is coming out of the PCM, then it would seem that there is something wrong with the PCM. Got someone you can swap PCMs with for a test?

The PCM is not going to be telling the fans to do anything once the key is OFF.

abilak

Okay, I am still confused.

While the C100 Clip is connected both the green and blue wires have voltage in them:

C100 Clip Connected Blue Wire Voltage
C100 Clip Connected Green Wire Voltage

With the clip disconnected, testing back toward the relays the green and blue wires have voltage. Why shouldn't they? This is going to the + to the iginition, right?

C100 Clip Disconnected Blue Wire Voltage
C100 Clip Disconnected Green Wire Voltage

Also, on the C100 Clip facing the PCM the green and blue wires both show "ground" -- I also tested every other wire in the PCM and they all showed "ground"

C100 Clip Toward PCM Green Wire Ground
C100 Clip Toward PCM Blue Wire Ground

Could someone please take out a meter and verify all the preliminary tests that I have done? Please make sure that my reading are really "incorrect". I still don't get it. My green and blue wires toward the pcm show "ground". The green and blue wires from the relay side show voltage. But, when I re-connect the C100 clip the fans DO NOT come on. If I take a jumper wire and jump the green or blue wire from the relay side to ground the relay(s) click and the fans come on. The fans are only running right after I shut the car off... as soon as I pull cooling fan relay #2 or pull the C100 clip, they DO NOT come back on, period.

Again, can someone just verify that my test readings are NOT NORMAL.

abilak

Shoebox... also, the wire running to the ignition... when the key is out (car off, ignition off) is this wire supposed to have power running through it?
I am referring to wire in the upper left of the schematic. Shouldn't the ignition switch power off/on to this wire (the relays)?

shoebox

On your car it is hot at all times and does not go off with the ignition. That schematic is from a 1995. They changed the feed in 1996.

abilak

Ok. Thanks for clearing that up for me... we'll that really confuses me then.. because if you look above and check out the pics.. when the car is off there is ground toward the PCM (dark green wire).. so, when I connect it with this "hot" lead the fans should kick on... they sure as hell kick on when I jump the dk green wire to ground. So I know the relay's don't stick.. because when I take the ground jumper off the fans stop.. the relays operate as they should. What other information can I give that will help determine the cause of this problem??

shoebox

When you look back toward the PCM (C100 unplugged), the grounds you see on the lead are with the key OFF? What is the ohm value of the grounds?