BillKerler
12-09-2006, 07:37 PM
1994 C280 - passenger side near firewall under the cover are 5 computer (control module) boxes. Is one of these the climate control computer box? Or is the climate control computer behind the fascia plate inside the cabin on the wood grain console? Does this computer have C-MOS electronics in it susceptible to static electricity destroying it? Do I need a wrist ground strap if I work on the box? I know I should disconnect the battery.
I have an intermitent problem in auto and economy climate control mode (regardless of recirculation on or off). I do not always get heat out of the vents UNLESS I raise temp setting to "HI" and then instantly I get hot air always.
So my duovalves and main control water valve seem to work. The heater core seems fine too.
The problem seems to be the electrical signal going to the solenoid valve controlling the main green vacuum air tubing line which then feeds the block of air tubing connections next to the diagnostic port (all of this is under the cover lid between the top of the shock tower on the passenger side to the firewall).
I hear the pneumatic dampers "whoosh" when I lose hot air so no longer does the vent air pass through the heater core. If I quickly raise temp setting to HI then as I said, immediately the the dampers reopen and hot air instantly resumes.
When it gets too hot, I select down to 92 F temp setting and back again the outside ambient air flows through the vents. I usually select recirculate at this point so I don't get hit with cold air on cold days. When it starts to get chilly in the car, I raise temp setting back to HI and again instant hot air comes.
The AC works fine and on normal 70 F days in spring and fall, the heater not working is no big deal.
But in winter it's a bummer constantly dialing in HI or 92F with and without recirculation.
All my vacuum lines look great and snug.
My air filter is clean.
Usually when I first start up and the radiator fluid warms up, the heater works just fine for 3 minutes...maybe 10 minutes...once in a blue moon it might even work for 30 minutes...but eventually it will stop working and as I've been saying the only way to get heat becomes using the HI temp setting.
Only after shutting down the engine and restarting, maybe it will start working again...usually but not always. Let it sit for a couple of hours and then again it will work for 3 minutes, or 10 or 30 or something finite.
I feel like I've got a bad solder connection in the computer box in that part of the logic circuit involving the heater core pneumatic damper control based on what all the cabin thermocouples are telling the computer the cabin temperature is.
When I select to HI, there must be a separate computer output that tells the heater core dampers to open and stay open 100% not involving the circuit in the paragraph above.
Any ideas? Has anybody else had this problem? Thanks
I have an intermitent problem in auto and economy climate control mode (regardless of recirculation on or off). I do not always get heat out of the vents UNLESS I raise temp setting to "HI" and then instantly I get hot air always.
So my duovalves and main control water valve seem to work. The heater core seems fine too.
The problem seems to be the electrical signal going to the solenoid valve controlling the main green vacuum air tubing line which then feeds the block of air tubing connections next to the diagnostic port (all of this is under the cover lid between the top of the shock tower on the passenger side to the firewall).
I hear the pneumatic dampers "whoosh" when I lose hot air so no longer does the vent air pass through the heater core. If I quickly raise temp setting to HI then as I said, immediately the the dampers reopen and hot air instantly resumes.
When it gets too hot, I select down to 92 F temp setting and back again the outside ambient air flows through the vents. I usually select recirculate at this point so I don't get hit with cold air on cold days. When it starts to get chilly in the car, I raise temp setting back to HI and again instant hot air comes.
The AC works fine and on normal 70 F days in spring and fall, the heater not working is no big deal.
But in winter it's a bummer constantly dialing in HI or 92F with and without recirculation.
All my vacuum lines look great and snug.
My air filter is clean.
Usually when I first start up and the radiator fluid warms up, the heater works just fine for 3 minutes...maybe 10 minutes...once in a blue moon it might even work for 30 minutes...but eventually it will stop working and as I've been saying the only way to get heat becomes using the HI temp setting.
Only after shutting down the engine and restarting, maybe it will start working again...usually but not always. Let it sit for a couple of hours and then again it will work for 3 minutes, or 10 or 30 or something finite.
I feel like I've got a bad solder connection in the computer box in that part of the logic circuit involving the heater core pneumatic damper control based on what all the cabin thermocouples are telling the computer the cabin temperature is.
When I select to HI, there must be a separate computer output that tells the heater core dampers to open and stay open 100% not involving the circuit in the paragraph above.
Any ideas? Has anybody else had this problem? Thanks