Background: System was converted to r-134 a few years back. Basically, the only thing that is still original is the condenser. I had a similar situation last year and I took it to an A/C mechanic (not MB) to check the A/C readings. He did empty, vacuum and recharged the system. It worked for a while. However, this is the present situation:
1) Hot air from the vents.
2) Compressor is turning.
3) Auxiliriary fan is not working. Jumped pressure switch and high temperature switch and the fan worked.
4) Readings from A/C gauges from Autozone today on a 90 degree Florida day: High side 150 and low side 80 with the A/C off. With the A/C system on, high side 150 and low side 115.

Based on searching this site, I thought it was low on r-134 but now, I suspect a restriction on the low side. Expansion valve, a/c dryer, ?

Any leads/suggestions?

__________________
J.H.
'86 300E

Those readings suggest that the compressor isn't working properly.

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I would expect high/low sides to equalize. This suggests an expansion valve or compressor blockage.

However, if you had a EXP valve blockage, the running results would be very high pressure on the high side, and very low pressure on the low side, more like 10-20 low, and 300-350 high.

Your running low/high pressures imply the compressor is not compressing.....

Jim

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14 E250 BlueTEC black. 45k miles
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I think he did not give the system time to equalize, so we can't use those readings for a proper diagnosis.
If the a/c just goes off, don't use those readings until they are equal.
Then we can tell you the correct possibles...

Bad compressor...? but, why would re-charging the system would make the system work (at least for a while).
The good news is that, at least, it is not the evaporator...That was a job!
I will start pricing a compressor...Any good remanufactured ones out there...?

Thanks for the help!

__________________
J.H.
'86 300E

What are the readings before a/c is turned on ?????
Are they equal???

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A Dalton

The settings should be the same before switching the AC on.

When you do switch it on you should be getting the values given here for high and low lines.

Whats the temperature inside of the cabin?

A blocked/broken condenser or bad reciver should be considered.

Did he put a BLACK light on the system??

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

The temperature inside the car was above 90. When I say hot air is blowing out of the vents, I mean HOT air coming out. Therefore, I also suspect the monovalve is not working properly...

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J.H.
'86 300E