Ole

My ac relay fails voltage test to compressor. I pulled the relay but it does not appear to be same configuration compared to Nichols diagram for '89.
I have a Gruner 970, see pics. My problem is matching the rs275-0218 relay to the circuit board. I'm lost with relays and the conversion pin layout in Nichols write up doesn't seem to apply to this relay. Anyone have experience with this one?

WallyP

Check this thread, and note that the url for dr. bob's excellent write-up is in the last post.

https://rennlist.com/forums/928-foru...placement.html

Ole

Been ther Wally, its where my confusion began.

dr bob

Ole--

I looked at the original realy in my 1989MY controller, and matched the pins by function to the new relay I found. You can do the same if you have the contact diagram for the relay you removed. The pin numbering for the original relay in my write-up was absolutely arbitrary, since there are/were no pin numbers on the original relay. I think I mentioned that in the original description. Should be noted that the relay in my 1989 was in a smal DIP package, quite different from the one in your picture. I can't see the connections from the pins to the relay internals on your original relay, at least in the pictures you share, so you'll need to map the connections to the pin numbers you've added before you can make a connection table for the new relay.

Ole

Thanks Bob, this is the schematic for the radio shack relay.

Ole

I'll post a map of the original relay , need to find a multimeter to do that...Ole

Ole

Using a multimeter this is the pin map of the original relay. Pin numbers correspond to those (in yellow) in the previous pic of the relay base.

dr bob

Ok:

ASSuming that you are showing the contacts in the relaxed/ de-energized positions...

Old Pins to New Pins--

Old pin 1 to new Pin 5
Old Pin 2 to new Pin 4
Old Pin 3 to new Pin 2
Old Pin 4 to new Pin 7
Old Pin 5 to new Pin 3
Old pin 6 to new pin 1
Old Pin 7 to new Pin 6
Old Pin 8 to New Pin 8

Ole

Yes the diagram is de-energized positions. I'm begining to understand how these relays function. Thank you for your help Dr. Bob. Now to rewire the new relay as an external mount, the easy part.

KRAUT

Ole,

I have the same "odd-ball" AC control head that you have. Did Dr Bob's pin-out translation work for you?

Thanks in advance

jpitman2

Ole, Unless your new relay has a higher Amp rating than the original, it may be good (in the long run), to fit a more robust standard relay out near the AC compressor to supply the current from the jump post, triggered by the current supplied by the relay mounted on the CC board above. I have just done this in my car to avoid having to do what you are doing down the track.
jp 83 Euro S AT 52k

Mrmerlin

Bump for updates

dr bob

OK... The original outboard relay I fitted in 1999 or so is still working perfectly. That's the installation I documented in the original posting at that time. I had grabbed a pretty serious industrial-strength relay at a store that's almost directly across the street from GB's shop, although the location was purely coincidental.

Since then, folks have identified a Radio Shack relay that seems to work, but has a different pinout. So the arbitrary pin numbering I used has to be adapted to the R-S relays assigned pin numbers.

Greg Brown has been refurb'ing control heads for a while now. Besides cleaning and restoring and testing a lot more than just the relay upgrade, he adds a fuse in the clutch circuit to protect the board from problems in wiring and the clutch coil downstream of the relay. From the factory, there is insufficient protection for that wiring.

Some folks have added an external relay near the jump post, tapping into the wiring at the 14-pin connector there to get a signal from the existing control head relay, and the feed to the clutch coil. I looked at that as an option early in the decision process, and decided that adding a relay outboard of the controller is cleaner and reversible, and less subject to damage during maintenance. For many though, it looks like it's an easier fix than doing surgery inside the controller.


That's my knowledge and experience to date.