Need used AC Relay 928 618 105 00 please
08-30-2010, 09:23 PM
#17
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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 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.
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Cymadesign (08-22-2022)
08-31-2010, 03:39 AM
#18
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Simpified it for ya!
Seriously though, if you want to restore the original function, have Doc do a little surgery on a CIS fuel pump relay, so it takes more RPM's (>~~500) to get the relay coil to pull in. It should then be a plug-compatible piece. You could build the whole thing into a 53B case OK, but the slim-profile 31b contact isn't included in the standard 53B base.
Seriously though, if you want to restore the original function, have Doc do a little surgery on a CIS fuel pump relay, so it takes more RPM's (>~~500) to get the relay coil to pull in. It should then be a plug-compatible piece. You could build the whole thing into a 53B case OK, but the slim-profile 31b contact isn't included in the standard 53B base.
08-31-2010, 08:08 AM
#19
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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.
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.
08-31-2010, 09:29 AM
#20
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Mark at 928 International came through with a used one for me - thanks Mark.
I would still like another if anyone has one.
I would still like another if anyone has one.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
08-31-2010, 09:32 AM
#21
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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.
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.
08-31-2010, 01:10 PM
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If you pm an email be happy to forward the pics of the relay.
08-31-2010, 04:53 PM
#26
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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.
08-31-2010, 08:37 PM
#27
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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.
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.
08-31-2010, 09:28 PM
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A/C relay for 86.5
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?
09-12-2010, 11:42 AM
#30
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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?