So now we have to find out if its the clutch, the power to the clutch or the control signal which switches on the power to the clutch. If you have a voltage meter with needle probes, turn on the AC and probe the dark green wire going into the compressor clutch with the red probe and ground the black probe to the battery negative. Do you see 12V during AC on?

George

 

I was looking at pictures on Rock auto and they all seem to have two wires, only some have the wires in a connector thing, and some have them loose, and both types are listed as automatic, really confused now, and why do the AC Delco ones have some sort of hose?

 

I don’t have a meter, but I may pick one up tomorrow while I’m out returning the used side view mirror Rock Auto sent me and find out, I should be going right past the parts store.

 

The PWM motor used in the auto Ac option definitely requires three connections to work: always on power (oraNge), the pwm signal wire (purple and white), and ground (black). Maybe the motor frame is grounded to the truck chassis, eliminating the black harness wire. A std motor just needs power and ground with no control wire.

George

 

I just now went out to see what my blower motor control module looks like. What I found is that it looks much like yours. There is a three-pin receptacle and three wires that come out. The ones that come out are Purple (heavy gauge), Black (heavy gauge) and Brown (smaller gauge). The black and purple go to to a plug that connects to the motor. The brown has its own separate female spade plug that went to a separate spade pin on the motor. I think the brown went to a ballast resistor that was deleted on the new blower motor I installed. So currently it is just dangling. On yours, for some reason the previous owner cut off the plug for the brown wire and fed it through a small hole in the cover for the motor. The brown wire is not supposed to do that.

Now, I was able to identify the components on the schematic I posted in an earlier reply. On page 1-174, within the box labeled "Blower Motor", you will see the wires that go from the "Control" to the motor; Purple (PPL), Brown (BRN), and Black (BLK). On the new modules you see at Rock Auto, you will notice that the only wires that come out are the purple and black with the brown one coming out of the plug the purple and black ones go to.

Then there are the wires that connect to the female receptacle on the motor control module; Orange, Black and Purple with a White stripe. These are the wires labeled 540, 850, and 760, respectively. Black is ground, Orange is 12V, and the Purple/White is the signal from the Electronic Climate Control Module. By splicing into the orange wire, they have tapped into 12 V. I can only guess as to why this was done. Perhaps the previous owner wanted to interrupt the power supplied to the motor control module because otherwise it had failed in a way such that it was on all the time?

If I was in your place, I'd consider getting a new module from a wrecking yard and hooking it up. If it still doesn't work correctly, I'd check what is going on with the brown wire disappearing into the black cover as that was not stock. Then if that doesn't work, I'd suspect the electronic climate control module that is in the passenger compartment with the control dials. You might buy one while your at the wrecking yard also while you are there.

 

Christine makes a good point that I had not considered. Yes the orange wire is power and so it is likely that either they are switching the power on to a traditional two wire motor or they are switching power off to a failed (on) PWM three wire motor/controller. I can’t see all of the wiring well enough to trace the entire hack.

George

 

Well I was just getting started when it started to monsoon, but I got some more pictures of my wiring before it started:


Close up of the splice

The brown wire leads to a screw on the blower motor

A better shot if the screw the brown wire is attached to

Another angle of the splice

Wires going to the blower motor

The blower motor controller connections

Another picture of the wires

Did someone modify the wire harness?

What I could see of the label on the blower motor

Another shot of the label

Still can’t see much of the label

The best shot I could get of the connector

 

OK, so I'm thinking that the blower motor was replaced as the original one in mine that I replaced, had a dedicated pin for the brown wire to connect to immediately next to the two-pin plug receptacle on the motor. What the previous owner has done is connect the brown wire to the frame of the motor, possibly as a ground. I'm guessing they felt it was necessary to do this instead of leaving it dangling. When I did my blower motor replacement, I left the brown wire disconnected and everything worked fine.

The switch does appear to be wired in series between the end of the cut in the orange 12V supply wire that goes to the motor control module. Again, I'd guess this was to interrupt the power supply to the fan to keep it from running because otherwise it the motor control module would normally be powered continuously, with the pulse-width-modulated (PWM) signal from the electronic climate control module (ECCM) on the purple with white stripe wire would be able to control all fan speeds (including off).

You know, the simplest thing to try might be to simply disconnect the brown wire from the screw used to ground it to see if the system will now work.

Perhaps the previous owner hooked up the brown wire before testing and then with the ground though the brown wire messing up the operation of the motor control module, decided the only fix was to install the switch when in actuality, it was the grounding of the brown wire that sent a bad signal to the motor control module. This is all speculation of course in an attempt to make sense of what the previous owner did. If you are lucky, there was no damage to the motor control module and it will work.

Another possibility is that the previous owner replaced the motor when actually, it was the motor control module that was bad. And then to confuse matters even more he (or she) also decided to ground the brown wire which was unnecessary.

Since you know the blower motor can work, I'd suggest the following:

1. Disconnect the brown wire and close the extra installed switch so that the motor control module is powered. Then see if the system will work.
2. If 1. doesn't work, leave the brown wire disconnected, leave the switch on the orange 12V supply wire closed, and install a motor control module from a wrecked Blazer.
3. If 2. doesn't work, then the problem is likely with the electronic climate control module (ECCM) not sending the correct PWM signal to the motor control module.

If you had an oscilloscope, you might be able to test if there is a PWM signal on the purple with white stripe wire to be able to skip step 2.

No matter what, I'm sure the system should be able to work with the brown wire disconnected.

 

Any idea if that is a manual or automatic blower motor?

edit: I tried what you suggested, I unhooked the brown wire, but that caused the blower motor to not work at all, I hooked the brown wire back up and now it works again (though still obviously not correctly.
I do not yet have another motor control module to test.

 

I picked up a multimeter and voltage tester while I was out today and will try and troubleshoot the air conditioner clutch later if it stops raining in time.