1985 300D Klima - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 09-04-2018, 11:29 AM

I have been reading up on Klima issues in these threads: Compressor speed sensor.
87 190D 2.5 AC questions
They deal with the speed sensor issues and the Denso compressors. There has been many times that I have done a Sanden retrofit on an '85, and can't get the compressor to engage. I have always just jumped the terminals to get the compressor going, in order to charge the system. Only on one car (my bro's) did I actually look for the fault. I found it had corroded terminals on the EGR computer socket and plug. A little wire brushing on the plug, and a good used EGR computer fixed the tach, and the compressor clutch problem. Since the 85's don't have the compressor speed sensor, the main cause of a non working clutch is the lack of tach signal. For Mxfrank, Diseasel300, and others- is there an easy way to modify the Klima so the compressor clutch will work as it should when called for by the PBU? I imagine the same circuit and components as used for the later models would work. However, I am not good at electronics, and most of the terms used in the above threads went right over my head. I am just looking for a way to make the '85 system work like the earlier models (no Klima). Most of the time the customer wants the A/C to work, and doesn't care if the tach works or not. They also don't want to have to remove a jumper if they want heat. I have no more good EGR computers left, so even if that is what is wrong with the next one I do, I won't be able to get the A/C going short of using the jumper. Thanks in advance!

Diseasel300 · #2 09-04-2018, 11:55 AM

Because of how the Klima relay works, it's not as easy as just jumpering something out or swapping in a relay if you want to keep all the functions alive that the Klima performs.

If you jumper the pins in the Klima relay, the compressor will NEVER turn off, even if the high/low pressure switch opens. You also lose the WOT cutout. Depending on the year model, a jumper will have to be installed to retain use of the kickdown switch (later models had a different design). The compressor will also engage immediately when the key is turned, there will be no delay on clutch engagement to allow the engine to start.

I've thought about making a module to bypass all that Klima crap, but finding a source of pins is problematic, the issue of having some whining person claim that the module "blew up their car", and of course the common issue of the cheapskates wanting something for free, it just isn't worth the time, effort, or money to develop it into an actual marketable product. The basic schematics are posted in the thread you reference and will "get you by" with reduced functionality if someone wants to take it on.

ROLLGUY · #3 09-04-2018, 09:59 PM

Quote:

Originally Posted by Diseasel300

Because of how the Klima relay works, it's not as easy as just jumpering something out or swapping in a relay if you want to keep all the functions alive that the Klima performs.

If you jumper the pins in the Klima relay, the compressor will NEVER turn off, even if the high/low pressure switch opens. You also lose the WOT cutout. Depending on the year model, a jumper will have to be installed to retain use of the kickdown switch (later models had a different design). The compressor will also engage immediately when the key is turned, there will be no delay on clutch engagement to allow the engine to start.

I've thought about making a module to bypass all that Klima crap, but finding a source of pins is problematic, the issue of having some whining person claim that the module "blew up their car", and of course the common issue of the cheapskates wanting something for free, it just isn't worth the time, effort, or money to develop it into an actual marketable product. The basic schematics are posted in the thread you reference and will "get you by" with reduced functionality if someone wants to take it on.

I am aware of what the jumper does, and it was only there to get the A/C charged. The A/C works as it should now that the EGR computer has been replaced. The only function I would like to see gone is the tach signal. Everything else needs to work as designed. If I had any electronic savvy, I would build one for myself. What about using the Klima enclosure and base (with pins) to build off of? I am sure junk Klima relays can be found. I probably have a couple lying around myself.

Diseasel300 · #4 09-04-2018, 10:16 PM

Harvesting a junk Klima for parts is exactly what I'd thought about. The motivation is just seriously lacking.