I should re-group and clarify.

It does not appear that I am receiving a signal from the AC controls to the relay.

 

Is the wiring to the relay original?

 

Andy
The relay is just an electrical switch, with two separate parts: A low amp solenoid activated part that when it gets current throws a high amp switch. So when the low amp pin gets feed from the aircon switch it activates the solenoid in the relay that clonks the high amp switch in the relay to send a high amp current to the compressor clutch.


So the aircon control should send 12 volts to the relay, ignition on. The relay itself is a switch that uses the low current from the aircon control to switch high amp current to he compressor. Therefore the relay should have 12 volts to one side of the HIGH amp part, all the time. This is your permanently live pin 30. The wire from the relay to the compressor carries the 12 volts that is always at pin 30 to the compressor. This wire should be attached to the pin opposite pin 30 on the relay, this is (over here) pin 87.
The wire from the aircon cabin control should be attached to one of the pins on the axis at 90 degrees to the pin 30 high amp pins. The other one should go to earth.
So if the relay works OK, and there is always current to pin 30, then you need a low amp feed from the cabin control to pin 86 (or the pin opposite it, pin 85, the relay does not care) and an earth from the other. Then you should find the pin opposite pin 30 (pin 87 over here) gets live when the aircon is switched on by the cabin control.
This link explains it a bit:
http://www.12voltplanet.co.uk/relay-guide.html
This diagram shows the schematic, but somewhat confusingly, in real life the pins are at right angles to one another, as in this photo on the left:



Schematic
Make & break relay The most simple form of relay. The circuit between terminals 30 and 87 is made on energisation of the relay and broken on de-energisation, known as NO (or vice-versa for a NC relay).
Greg

 

Do you have a ground/earth connection at socket 85 or 86?

 

There is a diode in the circuit, and if the pins are reversed won't that cause a problem?

 

Mac
On the solenoids I have, anyway, the low current side that switches the high current side, functions fine whichever of the low current pins is live and earth. The solenoid, in other words switches the same regardless of which of its two terminals is live and earth. After that, as far as I can tell, the wiring will not "know" what the relay pin is doing. If the relay has a diode in it, then maybe it will only switch when the low current feed is to one particular pin low current pin.
greg

 

I think that's correct, a wiring switch on the high amp wouldn't matter, but a wiring switch on the low amp side with a diode in circuit the relay wouldn't fire. Which is why I asked if he has ground at socket 85 or 86.

PS - I assume the diode is in circuit to prevent current going back to the Climate Control ECM

 

I do have a ground at socket 85 which is the black wire.

The wiring on the relay appears original to answer an earlier question.

 

Unless the schematic is wrong, it should be at 86.

Could you post a higher resolution photo of the wires going into the relay socket?

 

Schematic might be wrong. Just looked at the 90-91 schematic and it has pins 85 and 86 reversed from the '89 schematic.

 

After running through the tests in the Delanair manual I think I have a bad A/C ECU. And I also have a bad spare A/C ECU.

Which seems incredible. But, a new used one is on order and we will see if that fixes it....

 

Hey Andy,

With the relay pulled, and the system 'on' could you measure if you have 12v at either socket 85 or 86?

 

If no, then see if you have 12v at pin 20 of the A/C ECM

 

No voltage at pin #20. I followed the test procedure in manual and neither of the A/C ECU's I have are putting out 12v at #20.

I think what happened is that I hooked up my compressor wire incorrect earlier and then proceeded to blow both of my A/C ECU's while testing.

We'll see, a new ECU is on the way!

 

That may be the case, which is why that diode is in the circuit.
Sorry about that, wish I could help more.

 

Update!

purchased a new used AC ECU off car-part.com and got it today. Installed and now compressor wire is working as intended.

My mis-wiring fried my computer, and my spare. I'm an idiot.

 

Please tell us what 'as intended' is in this case


Cheers
DD

 

The new A/C ECU sends a signal through green/brown wire to A/C relay under hood, which then sends 12v through the green/white wire to compressor.

On my 89 the green/brown wire from the A/C ECU, or pin 20 on the ECU, wasn't activating when the fan switch was turned on because I'd attached the compressor wire to the wire going this wire, TO the ECU.

 

This IS an awesome thread - I needed it today for some A/C trouble shooting! Thank you all. Thanks for starting it up, bullittandy!
Hope everything is STILL working out for you

 

Resurrection post

My 88 which is wired like a 88.5 to 89.



Which relay is the compressor one out of the 3? Far right is starter relay