Air conditioner went to full heat! - PeachParts Mercedes-Benz Forum

Ohtooman · #1 09-22-2003, 11:23 AM

My wife was driving my 82 300D Saturday. Air conditioning was working fine (as fine as it gets). She turned it off and when she re-started it, it immediately went to full fan, full heat. I checked and the compressor is not turning when air conditioning is selected. Also, the seatbelt buzzer stopped working as well as the tach. Could this be electrical in nature?

Thanks

engatwork · #2 09-22-2003, 12:12 PM

Figure out which fuse supplies that circuit and replace it.

jhal · #3 09-22-2003, 12:21 PM

Sounds like a blown or corroded fuse. Looking at my '85 300D, it is probably fuse #14, 8 amps. This fuse controls several other functions that may not be noticed until they are needed.

Ohtooman · #4 09-22-2003, 12:45 PM

Thanks, guys.

lietuviai · #5 09-22-2003, 08:22 PM

I have a similar problem with my '85 300D only that its only an occasional one. Sometimes when I turn on the "EC" button to just have the fan blow, even with the coldest setting, it'll blow hot air. The only thing that sometimes takes care of the problem is when I turn on the A/C long enough to cool the air down in the car and then go back to "EC' mode, the hot air problem goes away.
Any ideas?

sublettm · #6 09-22-2003, 10:10 PM

My wife's car (84 300D) blows the AC fuse periodically. Have never been able to figure out why so I just keep a good supply of 20A fuses in the glovebox.

Mike

BobK · #7 09-24-2003, 12:26 PM

My '83 300D would blow the same fuse. Turns out the wire for the kick down solenoid on the transmission was shorting out to the transmission crossmember and would blow the fuse if I floored it. Replaced about 10" of bad wire and problem was solved.

190D22 · #8 09-25-2003, 04:40 PM

Well since the defrost button on the ACC turns the AC compressor on AND full heat, ...I would suspect something along the lines of leaky vacuum that makes it do full heat.

lietuviai · #9 09-25-2003, 06:13 PM

Quote:

Originally posted by 190D22
Well since the defrost button on the ACC turns the AC compressor on AND full heat, ...I would suspect something along the lines of leaky vacuum that makes it do full heat.

I never have had the problem in defrost mode only in the economy mode w/o the A/C on.

Grdenko · #10 10-06-2003, 02:32 PM

my '91 does that maybe once every six months. i just turn the car off and back on and the ac works again. no big deal

#11 10-06-2003, 02:40 PM

Whenever the vacuum or the electric power to the air distribution and heat system of the climate control system fail - the system defaults to DEFROST which when both vacuum AND electricity fail is full heat directed toward the windshield and side dash vents. If only vacuum or only electrics fail only one of the two may default to DEFROST. If vacuum is out from the pump - then the brake booster will be "out" as well.

Marshall