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Re: [GMCnet] a/c compressor not engaging [message #345325 is a reply to message #345275] Sun, 14 July 2019 14:35 Go to previous messageGo to previous message
emerystora is currently offline  emerystora   United States
Messages: 4442
Registered: January 2004
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Senior Member
Deb
I have sent this out several times over the years.

"1973 through 1976 models had two relays in that area. The one above the horn is the blower relay for the heater/ air-conditioning blower.
Late 1977 and 1978 models had a third relay at the top which was a delay relay.

The delay relay is the smaller relay at the very top of the panel. It has two leads - on mine they are brown and yellow and one has a male and the other a female terminal at the end of the leads. The leads are approx. 6 to 8 inches long. The female one connects to the male terminal on the lead to the blower motor. The male one leads to the short lead (purple on mine) that goes to the blower relay (terminal 1). If the delay relay burns out you can plug the male motor lead directly into the short female lead going to terminal 1 on the blower relay.

The blower relay (below the delay relay but above the horn relay) has 5 terminals. When the blower relay is mounted with the 5 terminals down, there are two on the left, one in the middle and two on the right.

On the back left side it is #3 which has a red/white wire that leads to a fusible link and that goes into the harness and connects to the red wire from the alternator to the center stud of the battery isolator.

On the front left is terminal #2. Mine has a dark blue wire that leads to the resistor package in the right side of the heater box.

In the center is terminal #1. Mine has a short purple wire with a female connector. The male lead from the delay relay plugs into this (on mine right now I have the blower motor plugged into this as my delay relay is bad and disconnected).

On the right rear is terminal #5. This has a short black lead that goes to a ground screw.

On the right front is terminal #4. This has an orange wire that leads to the heater controls on the dash.

Terminals 4 & 5 control the coil in the blower relay.

Terminals 1 & 2 are normally closed and operate the blower when in low or medium speeds.

Terminal 1 & 3 are normally open but when the dash switch is put in "high" or "max" it actuates the coil and the relay connects these terminals which give power to the blower directly from the alternator in order to get higher voltage and higher blower speed. At the same time it disconnects terminal 2 from the circuit.

This may be more than you want to know but if you have any questions get back to me.”

Emery Stora
77 Kingsley
Frederick, CO

> On Jul 14, 2019, at 12:58 PM, Deb McWade via Gmclist wrote:
>
> Hi Ken. Well I have gone through the fan speed switch yesterday and appears to be fine. Today I worked my way back from the motor, since that, for
> me was the most direct and easiest to visualize.
> No power going to the motor from the delay relay.
> Checked the delay relay - power going in (the purple wire from the blower relay - now yellow from PO) and through that little "jumper" you see in the
> wiring diagram?
> Nothing coming from what was the purple hot wire - now black by PO - that goes through the capacitor to the motor. I pulled the harness and confirmed
> with the voltmeter that the harness looks good (12+ v across from the incoming 'jumper' to the outgoing 'ppl').
>
> Having some difficulty with the main blower relay - some re-wiring underneath is making it a bit difficult to access half sideways/upside down and my
> eyes are getting very tired from the close up focus (have to dig out my really close-up cheaters!). But since the current goes through that to the
> delay relay, I know that it is at least partly working.
>
> Once my eyes are uncrossed, I need to check the wire between the fan switch to the relay (green by the diagram) and the blue going to (coming from?)
> the resistor pack
>
> I did pull the resistor just because it was easier than checking with the MM and test light. The coils are intact. The harness is FILTHY!
>
> Before I tried it, I wanted to see if it is a reasonable move to by-pass the delay relay with a jumper wire in the harness to see if that gets me
> power down the line to the motor. I see in the parts interchange that the delay relay shows as 'obsolete' and doesn't seem to have an alternative?
> What to do if it is toast? Can it be by-passed?
> --
> Deb McWade
> Logan Lake, BC, CAN
> "Li'l Sister"
> '77 Kingsley, 403, EBL EFI;
> TZE167V101404
> It's Bigger on the Inside!
>
>
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