Extremely Inconsistent A/C '87 300 SDL

[Harrison W]

So here is the story on the A/C of my 300SDL. In the last year I've replaced the A/C condenser, compressor speed sensor, high and low pressure switches, receiver dryer, I have four different klima relays, new push button unit, new ignition switch, and a new blower motor.

What happens is, I can feel the compressor kick on about 3-4 minutes after start up and it cools the air quite well. When I start to drive, I can feel a heavy load on the engine and during acceleration around 1800-2200 RPM's. I can feel the compressor kick off and not come back on for 20 or so seconds. It seems like when ever I try to accelerate at all, whether off the line or driving at speed, the compressor seems to kick off, and comes back on at idle. After about 20 minutes of this it kicks off, and won't come back on again, at all. But if I start up the car the next morning or even later that day, the whole process starts up again. It should be noted that when the compressor is running it runs very well and will freeze me out if it somehow stays on long enough.

I'm starting to get very frustrated with the whole situation since it is starting to get pretty warm here in Boise, and I've done everything I know how to do to get the system to work. What could it be?

[NJ300sdl]

Overcharged?

Maybe an expansion valve can clog like a orifice tube.

[sixto]

I'd say the Klima relay is flaky. Maybe JamesDean can rebuild it. I don't think more commonly available gasser Klima relays work with Diesels. You can substitute a simple on/off relay for the Klima relay but you loose the features that cut power to the compressor clutch if there's an rpm disparity or engine temps run high. At least try the simple relay to confirm the problem is with the Klima relay.

Sixto
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[Harrison W]

Originally Posted by sixto

I'd say the Klima relay is flaky. Maybe JamesDean can rebuild it. I don't think more commonly available gasser Klima relays work with Diesels. You can substitute a simple on/off relay for the Klima relay but you loose the features that cut power to the compressor clutch if there's an rpm disparity or engine temps run high. At least try the simple relay to confirm the problem is with the Klima relay.

Sixto
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That might be a good idea. The only thing is that I have several different Klima relays, what are the chances of all of them being flaky? It's a possibility, and at this point I'm open to anything. How would I substitute an on/off switch?

[sixto]

Originally Posted by Harrison W

The only thing is that I have several different Klima relays, what are the chances of all of them being flaky?

What are the chances of all of them being 20-30 years old?

Not an on/off switch but an on/off relay. These are my comments form 2005 with additional comments in brackets:

For more on the ice cube relay, given the common Bosch relay pin-outs, 86 and 30 connect to Klima socket 5 [+12V], 85 connects to Klima socket 10 [compressor trigger from ACC (ground)], and 87 connects to Klima socket 7 [compressor clutch].

I used regular [Radio Shack crimp on] bullet connectors and spread the contact for a snug fit in the Klima socket holes.

The objective is to bypass Klima relay internal switches and some system interrupts which over time become faulty or hyperactive. The evaporator temp sensor and refrigerant high/low pressure switch remain functional.

Sixto
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