climate control help? - PeachParts Mercedes-Benz Forum

126nut · #1 02-04-2012, 04:12 PM

On my 500 SEC.

I've had the dash out and replaced the bad pods and even had to pull it out again to replace a footwell driver side flap so I am getting frustrated here. It will just continuosly switch from heat (on the feet) to A/C cool (dash vents) on it's own with no difference as to what function button is pushed ( other than defrost) I hear the switches clicking on on off while it is alternating between heat and cool, I guess the clicks are the solenoids which are making the noise. Pulled vacuum on all the pods and they are tight and also ohmed out all the vacuum switches and they are good too. I am thinking pushbutton controller? The monovalve wouldn't have anything to do with this or would it? The sampler hose which goes up to the headliner is intact as well. I know from past experience that the climate controls on these cars are buggy but I'd expect it to be better than this.

Thanks and please help before I go out and buy the wife a KIA, (just joking)

sixto · #2 02-04-2012, 04:35 PM

Check the cabin temp sensor first . Make sure it's drawing air and not clogged with dust.

Sounds like the PBU (push button unit) isn't happy. If it's a pre-86, it'll be easy to open the unit and check the solders. I have sparky friends do that for me. Post-85 are more complicated since they incorporate a controller that's external in the pre-86 PBUs. Post-85 PBUs are less likely to revive by reflowing solder.

Sixto
87 300D

126nut · #3 02-06-2012, 10:17 PM

Thanks, I ordered a new controller so I'll let you know how it works out.

S124300 · #4 02-07-2012, 07:17 AM

Euro W124s with climate usually need the control board repairing / replacing or the relay changing. Those are Diavia units.
KIAs are good, reliable, cheap cars here in the UK - generally.
A millionaire friend bought a used KIA 4wd to tow his caravan and liked it. It didn't feel as nicely made as his Mercedes, but didn't rust or give him half of the bother.

126nut · #5 02-08-2012, 12:09 AM

Quote:

Originally Posted by S124300

A millionaire friend bought a used KIA 4wd to tow his caravan and liked it. It didn't feel as nicely made as his Mercedes, but didn't rust or give him half of the bother.

Yeah I think I saw that Utube video, real funny with the trailer pulling him backwards down the hill!!

126nut · #6 02-19-2012, 11:46 PM

Well that was expensive, $300 for a new pushbutton controller and it still does the same damn thing. Switches from heat at the floor to a/c at the vents in a rhthym of about every 15 seconds. I can hear the vacuum switches clicking and the pods flexing as it does the same stupid crap. I have got the service manual on cd and unless I have this Mercedes gizmo that you plug in I guess the only thing I can do is ohm out a few temperature sensors but not sure if they are even the problem. There is a box, "electronic temperature switchgear" mounted under the dash, maybe I will throw one of those at it and see what it does, can't be nearly as much as the pushbutton controller.

When I bought this car somebody tried jumping it backwards and it was dead when I bought it, blew the OVP, OVP fuse and the ignition module, wonder if maybe they fried something on the climate control?

Hit Man X · #7 02-20-2012, 05:09 AM

Are you referring to that silver box near the blower fan?

'James Dean' and I go around and around with the Gen I system trying to figure out why the hell I have no 'Low' fan speed on my SD. I think it is related to that silver box, but he is pretty sure it is incorrect wiring position. We have tried multiple PBUs, blower relays, etc

In any event, I have more issues with the Gen I HVAC than I ever have with the Gen II stuff.

126nut · #8 02-20-2012, 09:14 AM

My CD shows a blower switchgear and a temperature switchgear, not sure if they are the same part. I am not looking forward to it but I might be digging back into the dash here soon and start chasing them down. Need to find a parts car and just do some parts swapping first before spending the money on new parts. If I wait long enough it will be summer so if I can just get it to blow ice cold at the dash then I will be good for a while.

I did see an early W126 Euro sedan at the junkyard with the manual heating and cooling system in it, wonder how hard it would be to ****can the automatic climate control and put that in my car?