My AC clutch keeps trying to engage when the climate control is turned off. It is repeatedly grabbing very briefly, I'm not really sure where to start. Was looking for some ideas, I guess first I should unplug the power to see if it is an electrical or mechanical issue, thought maybe someone has experienced it. Also I noticed the engine idle keeps trying to compensate each time the clutch "grabs"

I can't figure out how to put a You Tube directly in my post but here is a link to it.

Thanks


300D AC compressor - YouTube

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
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Looks like it is pulling in electrically to me.

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Jim

Same opinion here.......

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96 E300d

Is it running in defrost mode?

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2001 SLK 320 six speed manual
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Looks like the same pulse timing as what goes to the mono valve.

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During Ac and Defrost mode the compressor runs and cycles normally, however during the normal cycle off time it still "grabs" like in the video.

The video was taken with the "O" button depressed on the dashboard control.

Is that what you are asking?

I have had a couple people say there is a good chance the problem is in the control head itself. Can I rebuild it, or replace it at reasonable cost?

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

it TOTALLY looks electrical to me.
you can see the plates engaging and disengaging...
NO idea how to troubleshoot the issue though. I'd start with the push button unit, and re-solder all the contact points. that system is klima controlled is it not?

BRIAN???

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Yes there s a Klima relay behind the battery, had to change that a couple of years ago.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

I'd start tracing backwards - next up from the compressor should the relay, right? Can you swap a known good one? Or put a meter across pins 85 and 86 on the relay.

It definitely looks like the relay is closing to engage the compressor, now you've got to figure if something is telling it to; e.g. a short or something else; or if the relay is failing and it's just doing it on it's own.

I will be working on it this weekend and trying some of the suggestions, any more ideas?

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

Well I finally figured this one out so I wanted to post because I hate it when people ask for help then disappear. I ended up unplugging the pressure switch and my wife drove it to work all winter, then when summer came we had an Infiniti FX so she drove that and the 300 just sat in the driveway all summer. Well this weekend I was determined to start working on the old and neglected gal. I spent Sunday afternoon removing and disassembling the pushbutton unit. There was no sign of burnt or cracked solder joints, everything looked great. I pulled all the boards and cleaned them with electronics cleaner and compressed air, as well as the switches. Put it all back and thought all was well until I drove it, the problem was still there.

Went in the house and pored over the schematic for a while then went to bed. Lying in bed I kept going over the schematic in my head when it suddenly hit me that the only way the compressor can run is when ground is supplied to it, since it is always hot at the Klima. The pushbutton unit normally supplies the ground to one side of the pressure switch, and with the pressure switch closed, the ground is complete and the compressor runs. This is when I realized IF THE WIRE BETWEEN THE PUSHBUTTON UNIT AND THE COMPRESSOR GETS GROUNDED BY ANY MEANS, THE COMPRESSOR WILL RUN.

Went out there today and almost immediately found the wire pinched at the compressor and making intermittant contact.



A butt connector and some shrink tubing later and all is well:



The AC compressor was changed by a shop some years back and I suspect the harness did not get put back properly. Is there a clip for this harness?

Anyway maybe this will help someone someday and remind everyone to CHECK THE SIMPLE STUFF FIRST.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

In my car which looks untouched in that corner, one low pressure switch wire makes 3 loops around the aluminum AC line in your picture then is zip tied to the bundle from the glow relay (the big bundle in your picture). The big bundle is zip tied to the lonely bracket in your picture. The pressure switch wire is zip tied to the big bundle closer to the compressor. The other pressure switch wire goes into a sheath that tucks under the port headlight. I'd take a picture but everything within spitting distance of the belt is coated with leaky front crank seal effluent.

Sixto
87 300D