Roger,

Think the AC problem is related to it being a 5 speed car? Put a rogerbox in it and I am sure your problem will be solved!

 

Roger--

The fuel pump relay receives system power on pin 30, with the switched output contact at 87. The AC speed relay socket has 15 and 30 jumpered behind, with source power appearing primarily at 15 but also at 30. If you put a jumper between 15 and 87, -or- between 30 and 87, -or- between 15, 30, and 87 all together, it will allow AC operation all the time. You should be able to see +12V at terminals 15 and 30 with key on and AC button depressed and the rest of the circuit intact. That +12V needs to go to 87, out from the CE panel at Q2 to the AC clutch via the 14-pin connector. If you don't see voltage at 15 or 30 in that relay socket, look at the freeze switch and the pressure switch next.

 

The 31b contact on the 78-79 AC relay is standard size. The fuel pump relay has 5 contacts, the AC relay only has 4. Attached is a picture of the AC relay with the cover off, this was non working off my 79. There's a pot visible on the end there, not sure if that's an rpm adjustment. Does the fuel pump relay have such an adjustment?

 

OK, the fuel pump relay mod was a hopefull speculation, since the functions are the same and the difference is the speed threshhold.

The circuit diagram for the car shows 5 pins used, although two (15 and 30) are shown tied together in the CE panel socket.

For some reason I'm not getting the full images that are being posted, so I can't see what you are looking at inside the relay can.

 

Mark at 928 International came through with a used one for me - thanks Mark.
I would still like another if anyone has one.

 

Roger,
It looks like it is easier/cheaper to buy a 78/79 parts car with a working relay in it, than find a new one. If you do find a source, let me know. I have not looked into the 79's AC very far yet, but I believe mine also might be bad.

 

I don't think that connecting the 15 bus to the 30 bus is a good idea...

 

It's not.

But it is just pin 15 and pin 30 on the relay that is jumped. Not the CE panel

 

It also looks like it only happens if the defrost is on also. Which is max blower speed.

 

Going under the premise that the pot inside the AC relay is to adjust rpm, if the fuel pump relay has a similar internal adjustment, then worse case scenario some short jumpers can be used between the CE panel and the fuel pump relay and the rpm adjusted so the relay energizes at >500rpms.

If you pm an email be happy to forward the pics of the relay.

 

I think this may be one of those cases where over-engineering turned in to over-the-edge emgineering. CIS cars have normal idle speed determined by a stop screw on the throttle, and AC operation includes adding some bypass bleed air around the throttle. The AC compressor actually adds little load at cranking speed, so I'm not so sure why the speed relay was really needed. The later non-CIS but pre-LHA cars have the AC idle air bypass but don't have the speed relay; that's what steers me towards it being needed only for CIS cars, but why? Anyway, I would certainly feel very comfortable using a jumper in place of this relay.

 

That would be consistent with PET saying the relay was used up until 82 - Euro S are CIS too. The relay would have phased out with the new HVAC control unit in '83.

Might be able to find used ones more commonly in Europe - Roger, ask on 928uk there's a few guys on there with early parts cars.

 

My A/C compressor was not turning on and the mechanic traced it to the mini relay in the control head. He told me he did not have access to a new relay and jumped it out. The A/C works now but it does not cycle properly. The car will get very cold then it will get very hot again before the cold air starts again. I think the A/C compressor is is cycling on and off the freeze switch. Does anybody know if this switch is avalable anywere?

 

Put in the used relay (thanks again Mark at 928 International) and my AC blows cold again.

 

There is a workaround to use an external ice cube relay, and some wires from the PC board. You can search on here and find the thread with the needed info or you can send it to me and I'll modify it for you and send it back. The relay is a known failure item, they all go out eventually.