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  #1  
Old 07-24-2005, 11:58 AM
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Weird C280 A/C Problem - Long Read

OK - Here's the background:
  • 1996 C280 Sport was in a wreck - AC worked fine before
  • Cluster had been replaced before wreck - old cluster had died
  • wreck broke the condensor


Here's what was done for the repair:
  • New Condensor
  • New Drier
  • New O-rings on all the lines

The Problem: The AC Now works randomly. When it does work it cools FREEKING COLD - so it's working normally, pressures look good on the gauges etc.

When it decides not to come on the climate control unit shows that it has 0 bars of pressure. But the gauges show otherwise. You can tell it's a false reasing because it will flicker between having pressure and not having pressure.

When it decides to run the condensor fans also operate normally. (Has a new condensor fan also).

It also gives a code about the cluster.

What we've tried:
  • Evacuating and recharging by weight several times
  • another drier
  • swapping the pressure sensor
  • swapping the temp sensor
  • swapping the climate control unit
  • swapping all the relays
  • running new wire from the sensor to the climate control unit

Still doing it - only thing we haven't tried is another cluster - but I'm at a loss about how the cluster could cause the problem - it works fine. And it wasn't causing any ac probs before the wreck.

We're stumped

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Old 07-24-2005, 12:09 PM
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Location: SE PA
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It seems you've covered just about everything. I'm by no means an expert on MB climate control, so someone else will have to answer with regards to instrument cluster involvement. What I would do at this point is go back to every connection in the wiring harness and make sure that each connection is tight an making good contact. Also, give the wiring a good wiggle and tug test. I've found wires broken inside undamaged insulation. Problems like these can be some of the hardest to track down.
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1989 300 SEL that mostly works, but needs TLC
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  #3  
Old 07-24-2005, 12:14 PM
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Quote:
Originally Posted by Moneypit SEL
It seems you've covered just about everything. I'm by no means an expert on MB climate control, so someone else will have to answer with regards to instrument cluster involvement. What I would do at this point is go back to every connection in the wiring harness and make sure that each connection is tight an making good contact. Also, give the wiring a good wiggle and tug test. I've found wires broken inside undamaged insulation. Problems like these can be some of the hardest to track down.

The car got a whole new wire harness about a year ago. We ran all new wire from the pressure sensor directly to the climate control box and it still does it.

We also spent an entire week to a end to end continuity tests on all the climate control wire harness - and nothing
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Old 07-24-2005, 12:36 PM
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Join Date: Jun 2005
Location: SE PA
Posts: 525
Quote:
Originally Posted by billabong132
The car got a whole new wire harness about a year ago. We ran all new wire from the pressure sensor directly to the climate control box and it still does it.

We also spent an entire week to a end to end continuity tests on all the climate control wire harness - and nothing
That's the problem with intermittents. When the problem is not actually happening, all tests will show good. Very tough to find unless you happen to catch it in the act. I'd try to measure the actual reading of the pressure sensor when the display reads 0, and I'd want to compare readings taken at the sensor with readings taken at the controller. Consider also the possibility that damage to another circuit is having an effect on the climate control.
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1989 300 SEL that mostly works, but needs TLC
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  #5  
Old 07-24-2005, 06:40 PM
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Quote:
Originally Posted by Moneypit SEL
That's the problem with intermittents. When the problem is not actually happening, all tests will show good. Very tough to find unless you happen to catch it in the act. I'd try to measure the actual reading of the pressure sensor when the display reads 0, and I'd want to compare readings taken at the sensor with readings taken at the controller. Consider also the possibility that damage to another circuit is having an effect on the climate control.

Yeah, hence the error about the cluster - hopefully someone knows what the cluster has to do with the climate control
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  #6  
Old 07-25-2005, 12:21 PM
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anyone?
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  #7  
Old 07-28-2005, 08:37 PM
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bump

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