OK, on the assumption that there will be no voltage between both leads in the connector, lets move on to power.

Check fuse IGN E (10A) and A/C Fuse (10A). Then find another relay in the box that is the same as the AC compressor clutch relay from a circuit that is working and swap them.

George

 

I tried testing across the connector and got nothing. I tested the fuses and they were all good, I tried swapping the relay with the horn and nothing happened, though it should be noted that the horn does not work either, but what are the odds that both relays were bad? However the only other matching relays were the fuel pump (I didn’t want to touch that, especially with the truck running), and another that I did not know what it did, so I left it alone.

I did however unwrap the sealed connector, and one of the wires is indeed green, it’s the one that connects to the black side.



Green wire.

 

Lets do one more thing while we are in this part of the circuit. We need to hotwire the compressor clutch to make sure it works, otherwise we might fix the underlying problem and not know it. The wiring diagram for this older truck does not show relay pin numbers so we have to do some identification. Pull the compressor clutch relay and use the continuity tester part of your meter and find the relay contact that is connected to the green wire in the clutch harness. We need to apply fused power to this pin which we can get from one of the other pins in this relay socket. Take the key out of the ignition and place your meter in DC voltage, ground the black lead and probe the other three socket holes. One of them should show 12V. Jumper that 12V fused source to the pin that is connected to the green clutch power wire and the clutch should click closed. If so then we have a good clutch and we will go find out why the AC control is not sending power to the clutch.

George

 

Not sure I understand that one, so I should find the hot plug for the relay, then run a wire from there to the black wire (the one the green wire plugs in to), then listen if it clicks?

Also, any idea which blower motor I have, based on the pictures and testing? Is it the manual, automatic, or something else?

 

Remove the relay. Leave the ignition key off. There will be only one hot contact and it will be fused which makes it safe. We need to probe that contact and get it to the positive wire for the compressor clutch. You can find which contact is for the dark green clutch power wire by taking the connector apart and find continuity from the dark green wire at the plug and the proper relay contact. Then put the connector back together and jump those two contacts at the relay socket. Another approach would be rig up a fused wire lead from the battery positive and a negative wire from the battery negative, pull the connector apart and energize the clutch wires appropriately.

There is a purple/white wire from the AC and heating control module to the blower motor. What happens to that wire?

George

 

Might be a few days before I can test that one, I don’t have any test leads, so I’m going to have to run out and buy some, trouble is my schedule is a bit harry until Tuesday at least, unless you have a suggestion?

I did go ahead and order a new blower motor controller though, I’m thinking about ordering a new blower motor too because I’m still not sure if it’s the right one, or what kind of damage a bad controller may have done. It sounds like it is squeaking intermittently too. What parts number should I be looking for? Rock Auto still has me confused, they have multiple automatic blower motors listed as compatible but some of them have a plug connector and some just have wires, and some have some sort of tube and some don’t, which one am I looking for?

 

I have no idea as I have never been into a blazer dash. Maybe Christine has more info, I don't remember if hers in auto AC or not. I see what you mean about the motors on Rock Auto not being consistent. BTW, that system has a bunch of extra sensors/motors and wiring. There can be so many things that could have failed so this may be a bit of an adventure. Since your short on tools, you might want to try the low pressure switch paper clip jumper described in the other active thread on AC. Thats jumping ahead but you might get lucky.

To jumper those relay contacts just strip the ends off of a wire and push them in, just dont force the contacts open too hard.

George

 

If you are going to buy a new blower-motor, which is not a bad idea if you are hearing squeaking, get one for an automatic climate control system with the molded electrical plug.

The motors listed as compatible that don't have the plug are ones that likely could work but you'd have to do some wire splicing. It is not worth the headache.

As for the drain tube, the replacement motor I got came with a tube. I suspect it is to help with draining any water that might get into where the motor is. I ended up using my original hose. You might as well get the motor with the drain hose in case you need it.

When reinstalling the outer cover, use a sealant that does not out-gas acidic vapors. I believe regular silicone will out gas and those acidic vapors could damage the electrical components. Black RTV silicone might be ok (I can't remember). I used this black adhesive/sealant as it was rated for use with electrical components. https://www.permatex.com/products/ad...ubber-sealant/

This video shows how to get the blower motor out and you can see where there is a tube that goes into the motor part of the whole blower-motor assembly. That is the drain tube you were asking about.

 

Here is the sound I’m hearing, is it the blower motor?

 

Is it the noise starting at the 00:07 mark? It very well could be the motor bearings. I'm assuming there was otherwise no other inputs to the HVAC controls. Right? The audio is not the best.

You mentioned earlier that you were concerned with the motor maybe being damaged by the control module. I find that unlikely but then again the previous owner really did a hack-job on the blower-motor so it might be worth to change out the blower motor anyway for that reason alone. Combined with suspected bearing noise could tip the balance toward definitely getting a new blower-motor.

You could try taking the blower motor out first and then seeing if you can feel any friction from the bearings when you spin the squirrel-cage fan by hand.

But, compared to the cost of a new blower-motor control module, a fan is cheap, even the most expensive one from AC-Delco.