We've had our 1986 300E for 15 years. It is in excellent condition, but the climate control has frequently been a problem.

This time, the heat is on full; blowers on top speed when in 'auto' no matter where the temperature setting is.

Here's the info from my check-out:
1. The aux water pump works but draws 2.45 amps.
2. The voltage (open-circuit) output to the mono valve is 5.5 VDC.
3. The mono valve resistance is 14.5 ohms.
4. If I disconnect the mono valve and jump 12 VDC to it, cool (not cold) air comes through.
5. I see some air bubbles in the refrigerant sight glass.

I'd like another opinion on my diagnosis:
1. Replace the original aux water pump
2. The original mono valve is okay (should I replace it?)
3. The ACC panel (5 year old rebuild) is bad and should be replaced.
4. I may have a freon leak to fix.

Any comments are welcome. Thanks!

Brent Smith
Atlanta, GA
USA