What's the temperature reading on the dash gauge when this event occurs?

I brought my 87 300d in for ac work ,mechanic converted it to 134a, fixed a couple o-rings,filled it up ,ran system ,and told me the compressor ran constantly, which he said was incorrect.Then turned off car and then all 134 a blew out relief valve on back of compressor. system was only blowing at 70 degrees he said. He said I need a new compressor.Sound right anyone? thanks in advance-Joh

It sounds like you may have a restriction in the system. Was the dryer replaced?

Usually about 90 degrees. It never goes any higher than that. It always sits at 80 or a little below.

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John
1986 300sdl
1985 380se

I only had the o-rings replaced,no dryer,whats a dryer?does this sound like a bad compressor, to me it seems like it pumps up too much pressure and doesn"t bleed off or cycle and stop pumping .

Then, something is amiss. The fan should never run at high speed until the coolant reaches 105C.

Most of us have never heard the fan at high speed.............I certainly have not.

The dryer is built into the receiver, and sits in the liquid line between the condenser and expansion valve. It was probably replace if o-rings were changed, because that opens the system to air. Additionally, the desiccant used in the old R12 dryer is not compatible with R134a and its oils, so it should always be changed for a conversion.

Also, there is a low-pressure cutout switch on the dryer, which should be replaced with a binary (high-low) pressure switch. Any replacement switch will be a binary switch, since it never hurts to use one for R12.

If you have a restriction in the dryer, the inlet line will be hot and the outlet line will be quite cold. The same goes for the condenser (or any other liquid-bearing part).

You Are absolutely correct!!!! What I am hearing (actually sensing it coming on ) is the low speed aux fan. I went out to test this yesterday. The low speed fan will come on and I can see my needles jump a little when it does. I guess it is just a little more draw on the electrical system.

I tested my high speed fan and it does work, but it never has come on by itself.

Thanks for helping me clarify this.

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John
1986 300sdl
1985 380se