1985 300D Klima and fuse box woes - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 04-14-2018, 06:41 PM

I just installed a Sanden retrofit in my brothers '85 300D, and the only way I can get the compressor to come on is to jump the terminals in the Klima relay socket (#87 to KL?). With the cover off the relay and it plugged in the socket, I can manually push the relay (left one) and the compressor will come on. I do know that the pressure switch on the drier is good. I am not sure what tells the relay to energize. I know there is a full throttle cut-out switch as well as a temp switch, and I believe they are both good. I think the temp switch connects the ground, and the throttle switch takes it away at full. Other than that, I don't know what would be causing the compressor not to engage. I have the terminals jumped so the A/C will work, but when heat is needed, the jumper will need to be removed. I have a schematic for the earlier models, but not the '85 with the Klima.
Also, there is no power to a couple of fuses. I pulled the fuse box out and checked all the connections, but no power is present on one red wire feeding a buss (fuse 8&10?). I used a GP relay fuse to add power to the buss from the working one next to it. This seems to be working, but I want to fix it right. The wiring diagram for an '83 (don't have one for the '85) is no help. Thanks in advance, Rich

SD Blue · #2 04-14-2018, 10:22 PM

Here's a diagram for the 85SD:
http://eva2.homeip.net/w126-1/Program/ETM/ACC83-85.pdf
It should be the same setup.

ROLLGUY · #3 04-15-2018, 11:55 AM

Quote:

Originally Posted by SD Blue

Here's a diagram for the 85SD:
http://eva2.homeip.net/w126-1/Program/ETM/ACC83-85.pdf
It should be the same setup.

I think the 126SD is different than the 123D. The 126 does not appear to have a Klima relay, or it is called something else. An actual wiring diagram would probably be best for finding the electrical path for both problems (Klima & no power on the buss).

ROLLGUY · #4 04-15-2018, 11:57 AM

I will be doing another Sanden retrofit on Thursday on an '85 TD, and I hope it too does not have any electrical issues that will prevent the compressor clutch from engaging!

Diseasel300 · #5 04-15-2018, 12:06 PM

Do the '85's have the 3-pin connector to the compressor with the tach output like the '86+ models do? If they do, that'll stop your compressor dead in its tracks. If the Klima doesn't receive tach input when the compressor is engaged, it will lock out the clutch thinking the belt is broken.

Diseasel300 · #6 04-15-2018, 12:15 PM

Speaking of tach inputs, the Klima also receives a tach signal from the EGR computer (EDS on the '86+). Does the tach work? If there's no tach signal from the EGR computer, the Klima won't engage the clutch. It expects the engine to be above a certain RPM before the clutch is engaged to prevent the clutch running while the starter is cranking.

ROLLGUY · #7 04-15-2018, 12:20 PM

Quote:

Originally Posted by Diseasel300

Do the '85's have the 3-pin connector to the compressor with the tach output like the '86+ models do? If they do, that'll stop your compressor dead in its tracks. If the Klima doesn't receive tach input when the compressor is engaged, it will lock out the clutch thinking the belt is broken.

No, it has the standard R4 with two wires. I think the 3 pin connector is on the Denso compressors.

ROLLGUY · #8 04-15-2018, 12:22 PM

Quote:

Originally Posted by Diseasel300

Speaking of tach inputs, the Klima also receives a tach signal from the EGR computer (EDS on the '86+). Does the tach work? If there's no tach signal from the EGR computer, the Klima won't engage the clutch. It expects the engine to be above a certain RPM before the clutch is engaged to prevent the clutch running while the starter is cranking.

Ah yes, you may be onto something there. I will check.