I need instructions on how to bypass/disable the speed sensor on a/c comp on 1986 190d so that the Klima relay does not realize the compressor misses a beat now and then due to belt slippage or clutch slippage.

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BRAD FRANCIS
1986 190D 160,000 mi.
SUMNER, TX

The only way to by-pass this function would be to either simulate it; which would be a trick or by-pass the whole relay. If thats your intention,depending on the year and relay jump the 15 or 30 to the 87 terminal.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Of course once you have done this, the compressor comes on whenever the key is on so it by-passes all the other problems that could be there. Not much good for diagnostics.

The problem with by-passing just the speed signal is that it is a dynamic pulsed signal and it is being compared in the electronics to the engine speed. It isn't a given at any particular time so it would be hard to reproduce and since the two signal aren't the same form (one is AC and one is DC they can't be just duplicated for comparison.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by Webmaster (edited 03-17-2000).]

THE COMPRESSOR RELAY CAN BE BYPASSED AS FOLLOWS,USING RELAY # 001 542 02 19 MAKE YOUR OWN JUMPER WIRES. TERMINAL #1 ON KLIMA TO #85 ON ICE CUBE,#10 KLIMA TO #86 ICECUBE ,TERM. #5 KLIMA TO #30 ICECUBE,AND #7 KLIMA TO #87 ICECUBE. CLUTCH WILL ENGAGE AND DISENGAGE AT PUSHBUTTON ASSY'S COMMAND.M.F.

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M.F.

THANKS TO GERMAN AUTOMOTIVE M.F. WILL THE COMPRESSOR STILL BE CONTROLLED BY THERMOSTAT CONTROL WHEEL? ALSO WHAT ARE YOU REFERRING TO AS ICECUBE?

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BRAD FRANCIS
1986 190D 160,000 mi.
SUMNER, TX

I have had to do this with 134 conversions because of the higher pressures. It does work. The ice cube is a generic term for the Bosch 5 pin relay. You can get one at any stereo shop... It will be controlled by the pushbutton and will cycle on and off yes./.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Problem. I've done this but dashboard control unit fails to output power to Klima socket pin 10. Tried a new control unit, no change. But does output power on pin 10 when Klima relay is installed normally. Something is missing that the Klima enables. Will investigate further.
John

The CCU doesn't output power to pin 10, it provides a ground.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I'm still working on this crappy mod. Bad enough it's compromised, it's not working as expected. I no longer think pin 10 is a ground, it's at 14 Megs to ground with a/c on. Pin 1 is ground, and I'm pretty sure Pin 10 should have power through the pressure switch in normal a/c operation. But instead, it's showing .75V. It could be that the system doesn't switch on until engine rpm is above 600, and the Klima is required for that. I have corrected my diagrams, and posted the latest but be aware that it's still work in progress:

http://www.peachparts.com/shopforum/diesel-discussion/386849-compressor-speed-sensor.html#post3735148

In the worst case, I can build a solid state circuit that can switch based on a .75V signal. It's getting to be a lot of work...

To bypass the speed sensor input I have used a klima from a w126/ 560/420, the multi belt system has no sensor circuit. Just plug and play, of course you lose belt protection

__________________
Paul

Diseasel300, Thanks for the feedback. Confirms what I was beginning to suspect from reading other posts elsewhere. GERMAN AUTOMOTIVE has the side of the cube relay coil opposite the side going to Klima pin 10 being connected to Klima pin 1, a ground connection. That led me to believe pin 10 would provide power.

So, instead of pin 1, I'll use the power source from pin 5 to connect to the relay coil opposite the connection to pin 10.

THE COMPRESSOR RELAY CAN BE BYPASSED AS FOLLOWS:
1. USING RELAY # 001 542 02 19 MAKE YOUR OWN JUMPER WIRES.
(P/No. Mercedes A 0015420219 / Hella 4RD004122-00)
2. TERMINAL #5 ON KLIMA TO #86 ON ICE CUBE, (Solenoid lead) (Klima power input)
3. #10 KLIMA TO #85 ICECUBE, (Solenoid lead) (Low pressure switch gnd input to Klima)
4. TERM. #5 KLIMA TO #30 ICECUBE,AND (SPDT common) (Klima power input)
5. #7 KLIMA TO #87 ICECUBE. (SPDT NO) (Klima output power to compressor)
CLUTCH WILL ENGAGE AND DISENGAGE AT PUSHBUTTON ASSY'S COMMAND

See note above, 10 is neither full power nor is it ground. Connecting to pin 5 means the compressor runs all the time, it's not a good choice.

I misspoke earlier when I said #10 was a ground. #10 is an output signal generated by the Klima and pulled down to ground by the ACC.

The Klima will output a voltage on #10 (~11V on my car) which the ACC pulls down to ground through the refrigerant pressure switch. It doesn't pull all the way to 0, I measure ~.8V like Frank does. The reason it doesn't go fully to 0 is because the switching is done by transistor in the ACC unit on '86+ models, they can't pull 100% to ground, the idea is to pull the signal "low" which tells the Klima to go ahead and engage the compressor.

So to recap, Klima generates voltage on #10 and if the pressure switch is closed (you have enough refrigerant), the ACC pulls #10 down to ground (low).

In my car, I found a failed darlington transistor pack in the ACC unit that caused it to fail to pull down. Rebuilt the ACC and it's been working like a dream.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

That won't work with a Diesel engined car. The Klima also controls transmission kickdown on a Diesel.

I'm going to respond to this on the other thread, there are too many threads on this subject at the moment.