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I recently replaced a defective A/C compressor. A/C not working, again. Checked fuse which is OK. Prior to shop assessment would like to check the relay(s), if any. Lacking a shop manual, can you advise on location of this? Secondly, does nl operation of A/C require closing side vents, which always spew heated air?
 

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SPEWING AND SPEWING

Spewing heated air? That's the hot radiator fluid pumping through your heater core. It's happened to me recently as well. To drive in a hot June day with heat spewing from your vents with no choice but to pop open the window and get a sinus full of pollen and dust and the vent heat still boiling away.

In my '86 300E, there is a steel pipe coming from the side of the water pump. That tube is attached to a 5/8-inch rubber hose that goes past the battery and into the passenger side of the cabin. On that rubber hose are two devices-- an electric water pump to supplement the mechanical water pump (for faster circulation); and an electric valve. The valve stopped working and remained in the opened (hot fluids flowing) position.

In the 190E, it looks like a valve that is operated by vacuum. It only costs $16.83. For the electric one for my model, it costs $86 bucks! I jammed a brass valve (thumb-turn) from Ace Hardware on the line, and the spewing heat went away. I wont need the electric valve for awhile. In your case, probably the vacuum line that opens and closes the fluid valve is leaking. Or there could be hard calcified sedimients in the fluid valve that keeps the valve from closing (and shutting out the heat).

You could do what I did and just plug the line to the heater core temporarily. When winter comes, unplug the line and you'll get gobs of heat. if you'll never use heat in your climate, then just jam a fat marble in the hose.

Or you'll need to buy a new valve since your original one is nineteen years old. And you can replace the vacuum line while you're at it.

That fixes the heat spewing problem. As for your A/C, you will have to do some troubleshooting (a matter of observation and deduction).
 

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