Well last year I was having trouble with intermittent A/C operation which would also quit along with the tach. I traced it to a connector behind the battery which was no longer insulated and was grounding out on the battery tray. Everything was fine for a while, then the A/C started cutting out again, only occasionally and this time the tach is not affected. When it cuts out, shutting down the engine and restarting will fix it.
The compressor is two years old. Two weeks ago I took it to the dealer and they pumped it down and recharged to verify correct charge. They also replaced one of the pressure switches, the one right next to the drier.
Also, the engine temp is ok, never over 100C and usually 90C with a new fan clutch, T-stat, radiator and genuine MB coolant.

I don't know what to check next. I was hoping for some input from some of the A/C guys out there.

Thanks, Brian

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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

Based on the fact that when your shut-off and restart the engine the compressor comes back on it sounds like a an AC compressor Speed sensor, or its related wiring problem. More likely the latter.

Another possibility could be a slipping belt.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Phil is most likely correct on this, but of his suggestions, the slipping belt is most likely. The sensor and wiring itself is usually okay.

Inspect the belt and its tension. Is the belt wet or oily?

Good luck,

Larry,

In my particular car, which had the identical symptoms described by Brian, the problem turned out to be the wiring related to the AC speed sensor. However, my '95 E300D model is notorious for having wiring harness problems, so this may not be the case here.

I agree that in this case the belt, or its tensioner could be a more likely cause.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

Well thanks guys, I had considered the speed sensor. The belt was replaced with the compressor 2 yrs ago, but I didn't think of the tensioner. Also, there is a chance oil or power steering fluid might have got on the belt, I'll take a look tomorrow. One horrible thought I had is what if the new compressor gets too hard to turn sometimes causing a momentary belt slippage. It DOES occur only after a restart on a warm engine when compressor head pressure would be at it's highest. Or maybe it's just a cheap belt. I'll try the belt/tensioner first, then maybe the speed sensor. I'll be sure to let you know if and when I figger it out.
Brian

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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 would not exactly consider a two year old belt "new." INSPECT everything before replacing parts.

Good luck,

Well the belt still looks new, no cracks or glazing, no oil. Even tho it's 2 yrs old the car is only driven 5-6K per year. The tension seems to be very tight altho I don't know the proper procedure for checking it. I remember when I changed the alternator in April I could barely get the belt back on with the tensioner completely unhooked. Maybe I'll have to wait for the AC to fail when I can pull it into the dealer and let them check it before I shut it down.

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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

Where is the arrow on your tensioner? The belt can feel tight, but if the tensioner is not holding, it will slip under load.

Good luck,

Larry,
I cannot figure out what you mean about an arrow on my 603 belt tensioner. When I look in the service manual it only describes checking the bearing pin for firm seating and that the collar of the bearing pin must contact the timing case cover. And that the idler pulley must not exhibit any alignment faults. And it also says these parts must be checked on the 1st design up to 10/85 with no mention of what to check on later production.
Anyway I am still suspicious of the compressor or another pressure switch. The dealership changed the switch which was located right next to the drier. I don't know if that was the hi or lo pressure switch. I will look it uo and maybe have the other one changed out. The A/C quit again today on my wife as she was leaving Target. It always happens after the engine is good and warmed up, then shut down for a short time. I know from experience that the highest head pressures will be encountered during that scenario.
I appreciate your help very much. By the way, do you know anything about the Isuzu NPR equipped with the 4 cylinder diesel?

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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 only know that in general i believe isuzu is respected for their diesels.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.