HVAC works on and off in 1991 300 TE: What could be the problem?
Thread Starter
Senior Member
Joined: May 2002
Posts: 471
Likes: 1
HVAC works on and off in 1991 300 TE: What could be the problem?
The automatic climate control system in my 1991 300 TE has started acting up recently. Sometimes it works fine, but then the next time I start up the car no air comes out of the vents, no matter which fan speed or temperature I select except for the natural hot air flow passed on through the engine bay created at higher speeds. The recirculation button also doesn't work when this occurs. Then, after driving for a while, the ventilation suddenly comes back on, ac and fan speeds work normally. I have replaced the blower motor, but that didn't solve the problem, the fuses also look good. Someone told me to move the key back and forth in the ignition 2 setting as a worn contact could cause the problem, but this also didn't help. Any other ideas?
Super Member
Joined: Aug 2005
Posts: 801
Likes: 1
From: Mercerville New Jersey
1991 560SEC Teal 1989 420SEL Ice Blue 1984 500SEC White
I had the same thing on an 89 420SEL. Sometimes the control unit would alow things to run normal, and other times no response at all. Checked all the fuses and the 30 amp inline fuse also. Mine turned out to be the control unit. I was on the road and had no choice but to buy a new unit from a stealership.
I have had no problems since, that was 6 years ago.
Bruce
I have had no problems since, that was 6 years ago.
Bruce
MBWorld Fanatic!
Joined: Jun 2005
Posts: 1,468
Likes: 0
From: Socialist West Coast
95 E320, 19 Ram 1500 Hemi, 21 GLS 580(wife)
sometimes the switch panels go bad and need soldering to fix cracks in the circuitboard. I would do a search on how to repair those since there has got to be someone out there that has posted on this before, I am just not positive where that is.
MBWorld Fanatic!
Joined: Apr 2007
Posts: 2,381
Likes: 29
E
I had that problem orginally on my TE. I fixed it through resolding some bad connection points IIRC. Once resoldering was complete, we tested and it was intermiddent so I went back and tried again this time bingo 
