1983 c20 blower only works on high

[ZXT]

I am the OP though..

[ZXT]

Thats the source of the confusion.. mine is an 83 (As the title of the thread says) and the gramps77 guy with a 77 mixed you up.

Also, good information, Ray. I'll check those places tomorrow and see what i can find.

[rich weyand]

Wow. I really went off down the bunny hole. That's the problem with getting old.

Looked back through the list. I answered the 77 guy, then you came back with your questions and I was still thinking on him. Very sorry, sir.

So, still need to know. Do you have A/C?

[ZXT]

Not a problem. I've done it a few times myself.

Yes, it does have AC.

Here's what I'm working with (If the links work..)

[rich weyand]

Excellent. OK, here is the diagram for the 1983 RPO C-60 AC.



You can see that HI is unique. The orange wire 52 from the switch powers the relay, which connects red wire 2 from the junction block to purple wire 65 to the blower motor.

For MED2, MED1 and LO, the purple wire 65 to the blower is connected to the dark blue wire 101 from the resistor pack. There are three resistors in the resistor pack. The longest one is fed constantly from the brown/white wire 64B, which is your LO position. The MED1 position feeds a shorter resistor through the tan wire 63. The MED2 position feeds the shortest resistor though the light blue wire 72.

For LO, MED1 and MED2 all not to work, you have only a couple of possibilities. The brown/white wire 64B could be broken. Read the voltage at the resistor pack on the brown/white wire: it should be hot all the time if any heat or cool mode is selected and the ignition is on. Do this with one of the LO/MED1/MED2 fan positions selected, so that you are sure it is not a high resistance connection that is enough to drive the voltmeter but not the blower.

The second possibility is that the dark blue wire 101 is broken, as Ray said, or shorted. If 64B were shorted, it would blow the fuse, but 101 could be shorted and not blow the fuse, because there is a resistance there in the resistor pack. Read the voltage on this wire at the relay, again with a heat or cool mode selected and the ignition on, and with one of the LO/MED1/MED2 fan positions selected.

As Ray said, it could also be that the relay is fused onto the normally open contact, bypassing the resistor pack, or the normally closed contacts could be fried, not making connection for LO, MED1, and MED2. You said you had changed the relay, though, so that is unlikely. You can check it by comparing the voltage on the dark blue wire 101 at the relay with the voltage on the purple wire 65 at the relay when LO, MED1, or MED2 are selected.

Those are the only three places I can see that are 1) common to LO, MED1, and MED2, and 2) not shared with HI.

[ZXT]

I'll check for voltages and get back to you later today. I'm pulling the engine out of my fathers '71 camaro so that will occupy me for a few hours.

I'm really terrible at reading wiring diagrams, so you explaining that out is a big help.

Thanks!

[ZXT]

Sorry it took me so long to get back.

The brown/white wire and the blue wire both have voltage to them.. It seems that every wire that's supposed to have voltage does. I'm going to pickup another relay just for the hell of it and see what that does.

[ZXT]

Relay was bad. Problem solved.

Thanks for helping out everyone. I appreciate it

[rich weyand]

Excellent! I love it when the magic works.