1985 300SD 617 Aux Fan & A/C Thoughts + Help Needed - PeachParts Mercedes-Benz Forum

Hit Man X · #1 05-26-2009, 11:04 AM

FINALLY finished the rebuild of the AC in my 300SD. I easily spent a week alone flushing the system as it was that disgusting and a few evenings alone working on aligning the bastard W126 expansion valve a few times to flush the evap core... whoever allowed that to be stuffed in there needs their ass removed. Had to track down proper fasteners for the compressor (the washer shims), rebuild the harness under the hood, and the like thanks to the PO.

Per the usual, I did an over night vac, held vac, then ... no compressor turn on.

I did find this thread KLIMA Basics missing from this forum which is helpful, I DO have power from the PBU to the Klima pins

(which I suppose means the PBU is good) but nothing from the Klima to the dryer or comp.

I did jump the compressor and the system is now full of Dichlorodifluoromethane but obviously, I would like to fix it properly.

I appear to have a fried connector (tracer? I do not know the proper term) on the PC board so I'm going to get a new Klima for sure. What the hell do the two relays in the Klima do? Do both have to trip for the clutch to lock?

On a related note, my aux fan isn't working. Direct 12V makes it run high speed so at least it works that way. It will not come on at the fan connectors at the dryer.

Where is the relay for this and where is the resistor for this?

Thanks

Graplr · #2 05-26-2009, 12:28 PM

Yep, that exp valve is a b#tch. I was on my head for many hours trying to get that thing in last year. It is much more accessable in the 300Ds.

Only one pin needs to have 12V for the clutch to lock and compressor spin.

I would check your cord at the compressor. On mine the plugs were pushed back and it was not making a connection. If you are getting power to the pins on the drier, you could just fabricate your own cord to the compressor.

I would first run a jumper directly to the compressor with the engine on to see if you can get it spinning.

Also, I would double check all the wiring at the drier as it seems you may have some things switched around.

ah-kay · #3 05-26-2009, 01:18 PM

I was looking at the 86 300SDL ( may be similar to your 85 SD ) wiring schematics and the wiring is as follows:

The A/C system includes by not limited to the CCU, Klima relay, K9, K10 relays and the pressure switches at the rec/dryer.

1) I am not familiar with the internal working of the Klima relay, it controls the compressor and monitor engine speed. The low pressure switch goes to the Klima relay and I sure you are familiar. Klima relay has internal electronics and I have not opened one up, not yet anyway.

2) The high pressure switch goes to the K9 relay, through a pre-resister to the aux fan.

3) The engine temperature ( 110 degree C ) switch goes to the K10 relay, by-passing the pre-resister to the aux fan.

4) In the 86 300SDL, K9 and K10 relays are inside the main fuse box.

5) Do not know where is the pre-resister. May be you can follow the wiring. I will look at the Manual or car if I get round to it in the evening.

This is how I read the schematic.

Hit Man X · #4 05-26-2009, 08:14 PM

Wiring is good at the comp when I jump the pins at the Klima relay, I have 12V there.

I can't seem to locate the fan resistor on the '85, I'm sure it's hiding in plain sight.

Also, with the high speed switch at the thermo housing grounded, I can't get the fan to come on either. So tis something before this. When I jump the fan relay itself "B" at the fuse box, fan comes on.

ah-kay · #5 05-26-2009, 10:00 PM

On my 300SDL manual.

The pre-resister is marked as R15 and is shown separately on the schematic.

The relays are marked as

K9 - Relay, Aux fan
K10 - Relay, Aux fan, pre-resister.

This leads me to believe the resister may be inside the relay K10.

Hope this help.

Hit Man X · #6 05-26-2009, 11:57 PM

Resistor is under the master cylinder. Great.

I can jump the aux fan at the relay in the fuse box and it comes on, if that tells us anything.

Does the aux fan for the low speed function on the AC run through the Klima?

ah-kay · #7 05-27-2009, 12:34 AM

It is great that you found the resister. I could not find it in my 300SDL and I do not want to lift the fuse box, too much hassle.

Anyway, I am not sure what do you mean by slow speed function. The aux fan can be control by K9 and K10 only. Klima plays no part in it as far as I can determine. K10 is only a ON/OFF relay controlled by the rec/dryer high pressure switch. The 12v from fuse 13 goes to terminal 30 of relay, through the relay, to the resister and then to the aux fan. May be it can attenuate the speed a little with the resister. I am not sure.

K9 is control by the temperature sensor on the engine block, switch at 110 degree. The relay is connected directly to the aux fan, by-passing the resister.

I think the Klima relay is all to do with the compressor control and monitors the engine speed. I may be wrong as I have not worked on this part of the circuit before.

Hope this help.

Hit Man X · #8 05-27-2009, 12:52 AM

My SD is October, 1984 build. So it has the ARV turbocharger but the standard 722.3 trans... weird stuff.

1985 SD only has five silver relays in fuse box (maybe the 5th is the low speed relay?) doesn't have it setup like the SDL. There are some others in the box, including the OVP, compressor time delay, rear window defroster, wiper delay, etc.

I was under the impression the 1985 617 had a two speed aux fan???

It does have a larger fan like found on my SDL.

The high speed cut on is on the thermo housing @ 100°C, this runs back into Aux Fan Relay per the manual. "Pre Resistor" branches that and the Pre-Resistor Relay.

I can only assume the Klima is called the "Electronic Unit for Temperature Control" on this car.

Manual I am going by is on Page 62, for the 1983-1985 MY Diesel W126 cars if any of you electronic masters out there wanna lend a hand.

ah-kay · #9 05-27-2009, 01:03 AM

I am sure you can crack it if you persevere. The circuit is relatively simple if all the components are in good order, the question mark is the Klima relay as it is a 'black box'.

Post your result when it is all done.

Hit Man X · #10 05-27-2009, 01:11 AM

I try to update threads once I reach then end.

FROM what I can gather, the aux fan doesn't run thu this 617A relay. It just seems to be the compressor clutch, the kick down solenoid + switches, the evaporator temperature probe, and the pressure switch at the dryer.

I wish I could find out what the other pins do - 87K, VL, and GM+. Guess I could pull the colors then see what they correspond to via the schematics.

JimmyL · #11 05-27-2009, 01:13 AM

Granted, my '85 is a W123, but this jumper on the Klima got my compressor working.....

Hit Man X · #12 05-28-2009, 02:06 PM

New Klima relay showed up via the friendly shippers.

Tossed it in, problem solved for the AC.

Still no Aux fan on low for the system when hot (I do have high speed when grounding the sender, blew my hair all over the place)... swapped relay with the mystery relay (YES it's the low speed one, so update your ETM accordingly).

So what does that tell us? Relay WAS bad AND 1985 cars DO have a high and low speed fan.

I have my weekend open so I am going to try to pin out the three mystery pins on the Klima relay so we can have them on hand. 87K (hm, like the 8mm Mauser 98K I have

), VL, and GM+ I can only assume those three run to the pressure switch and fan switch, but I'll check via the wire colors.

ah-kay · #13 05-29-2009, 01:23 AM

The pre-resister R15 is a beige color ceramic type resister measuring 2" x 1/2" tug under the brake booster. It is difficult to find, let alone to get to it.

The Aux fan has 2 speeds. The low speed is attenuated by the resister for the A/C. The high speed by-pass the resister for the motor running temp. Nothing special and no electronic control.

Hit Man X · #14 05-29-2009, 06:20 PM

Didn't get the pin outs as I can't get the damned plug out of the fuse panel, but it looks like the last three from the Klima relay are for the two wires to the pressure switch and the other goes to the fan switch.

Hit Man X · #15 06-05-2009, 12:34 PM

Pin 2 - Green/Black

Pin 4 - Brown/Blue

Pin 6 - Red/Green/Black