86'928S MeteorGrey

So I've been tracing the factory schematics to try and determine the correct orientation of the Radio Shack 276-0218 relay when replacing the odd pinout of the '83 and '84 model year Gruner 970 relay. The Gruner 970 does not have a schematic on the case like most relays. Furthermore, the pattern of the relay itself is different than the parallel 8 pin configuration of the 87+ relay. It's more of an offset 6 pin relay with 2 separate pins that are indeed the coil.

What I have found is that although the boards are completely different in design, the pins on the connector are identical in where they go on the control board. So I created a drawing of the original mod provided by Dr. Bob that includes the connector pin numbers. This 1st drawing shows the 8 pin original location with the Radio Shack relay on the right. I've included photos borrowed from Dwayne's HVAC relay repair thread, others that show the Gruner 970 relay for reference, and closeup photos of my 84 HVAC board. I've also attached the schematics from the 87 and 84 model year AC head.

I then created another drawing that traces the relay pin holes that correspond with the connector pin in the opposite direction to determine the correct location for the new relay.

I'm not completely sure this is correct. I've poured over drawings and schematics from the different model years and I'm pretty sure it's right, but I'd really like to get a confirmation from any or all of our resident electrical geniuses before I start soldering.

I've got a new diode to replace the burnt one on the board and I'm itching to get going. Hopefully this process won't give you as much of a headache as it's given me...

If this all works out, I'll post the results to Dwaynes HVAC thread to help future victims. I sure hope this is correct... I'm ready for cold air again!

Thanks!

WallyP

While I haven't checked it, that looks like valuable work.

I hate it when someone has an electrical mystery on an '84 - the wiring diagrams for that year are virtually worthless.

86'928S MeteorGrey

I've looked it over 10 more times, but still need a second set of eyes to confirm...

NOTE: The Relay Pin Mapping Chart below is for the lower (87+) board to relay conversion. The upper photo of the 84 HVAC board has the numbers of the actual pins on the new RS relay. PINS 1 and 2 on the new relay ARE NOT USED.

Don Ashe

This looks correct to me.
On the Gruner relay, using your numbering (can't read the numbers in the photo):
pins 7 and 8 are indeed for the coil
pins 1 and 2 are the 2 NC contacts (unused)
pins 3 and 5 are one pair of NO contacts
pins 4 and 6 are the other pair of NO contacts

On the schematic for the edge connector:
pin 7 (from A/C switch) goes to one side of relay coil
pin 4 (ground) to the other
pin 5 and 6 go to one set of NO contacts
pins 8 and 9 go to the other set

The PCB traces in your last photo comply with this, although I can't verify the trace for relay pin 7, as it's on the other side of the board, under the relay (you can see part of it).

Once you've got it all soldered up, put 12v across pins 7 and 4 of the edge connector and make sure the relay activates.
Then put a meter across edge connector pins 5 and 6 ( there are also 2 test pins on the top of the board for this) and make sure you have continuity when the relay is actuated, and none when it is off.

Do the same continuity test across pins 8 and 9.

If all that works, you're done.

HTH,
-don

86'928S MeteorGrey

Don,

Thanks for the inspection. I'll solder it up and post the results.

Best Regards,

Mike

Mrmerlin

Mike did you ever finish this project?

Alan

I don't think '83 & '84 are in fact the same configuration as OP suggests... '83 has a SPST relay configuration (only 4 pins used) just like '80-'82.

'84 to EOL was a DPST configuration (6 pins used).

Not sure what years the Gruner 970 was used Vs. the Gruner 202 they seem functionally equivalent - assume there was a reason for the change...
OP - I believe from your focus that you have an '84 - so I assume we know Gruner 970 is used in 1984

Any one know for sure about 1985 & 1986? I do believe 1987-1995 was all Gruner 202.

Chronology (as best I know): Year(s), Configuration required, (equipment used & notes)

1977-1979 - no relay in head unit - (full size Bosch SPST clutch relay on CE panel - This is the best way to do it)
1980-1983 - SPST mini-relay on HVAC head unit (what is the relay ID? - assume SPST/SPDT...)
1984-???? - DPST mini-relay on HVAC head unit (Gruner 970 (DPDT) until what year?)
????-1995 - DPST mini-relay on HVAC head unit (Gruner 202 (DPDT) starting what year?)

Alan

Mrmerlin

Alan I am updating the 2 HVAC heads,
I just removed two Gruner 970s from the boards with build dates marked 20 Jan 1984 and 24 June 1984 .

The June 24 board was in my 85 Euro and is slightly different than the earlier board.

This 24 June board smoked/ burned the tracing on pin 10 of the top side where the slider is, this damage occured about 24 MM in from the wire connector trace.
there isnt continuity from pin #8 wire I soldered on the RS relay to pin 9 of the topside of the board so something else has changed.

NOTE the other board seems to be fine as per the wire diagrams I am following
I should post pictures so you can have a look

On the Pictures, the boards of the first picture and the third picture are from the same board the 85 Euro.

On the 1 st picture I dont have continuity from pin 9 to where pin 8 of the RS relay swill connect,
Also at the pin 7 of the relay where it would connect to pin 12 of the board I have continuity and also have continuity at pin 13 of the board.
NOTE the other board only has continuity at pin 12 to 7 of the relay and pin 9 on the board goes to pin 8 of the relay.

NOTE I soldered the white jumper wire onto the board in picture 1 to replace the trace that burned up.

Do you have any ideas ?
It appears in picture 3 that there is a resistor soldered onto the board and the traces have holes drilled through them

Bill Ball

Just to add to the database, here's a thread about a 90 S4 AC controller I worked on in 2007 that had a Matsu****a DSP2a-DC12V-R with different pinout and wiring traces than the expected Gruner 202.

https://rennlist.com/forums/928-foru...y-stumper.html