relay question - PeachParts Mercedes-Benz Forum

#1 10-04-2004, 01:20 AM

When my car is in Heat mode, I can hear a relay clicking behind the glove box...I know there are relays out there behind the false firewall....should it click constantly, sounds like a clock ticking? Also, only when it's in heat mode, as it's clicking, it eventually cuts everything off. No fan, no control, no nothing. Zilch! Then after about 2 minutes, it clicks and comes back on. I've replaced the blower motor as someone suggested last winter and it needed it badly (commutator was really worn and gouged out) and I thought that fixed it...but it didn't. While it's working properly, the climate is comfortable...whatever I have it set on it seems to accomodate appropriately...it just stops. My aux water pump works fine. Once on a really hot day in stop and go traffic, the a/c and climate control and turn signals all stopped. Car was parked for a few minutes and after it all cooled off a little, it all started working again. Is this a failing relay?

#2 10-04-2004, 02:52 AM

I unplugged the aux water pump and took a drive tonight while it was 48 degrees outside....heat worked fine, I could still hear the ticking of the relay, but it didn't kick the heat out. maybe the aux pump is over drawing current...but is that relay supposed to constantly click?

mctwin2kman · #3 10-04-2004, 08:12 AM

Is it your OVP relay or maybe the Climate Control AC Relay? They are both behind that wall!

#4 10-04-2004, 12:32 PM

I know both of them are back there...I just need to know if that constant clicking like the rhythmic ticking of a clock is normal...not an every-once-in-a-while click...constant

mctwin2kman · #5 10-04-2004, 02:14 PM

Doesn't click on my 1986 190E!

#6 10-05-2004, 01:12 AM

I didn't think that was normal...if it were, wouldn't it do it in cool mode too? I guess I'll get some new relays...maybe that will solve my aux. cooling fan problems too. Now....part numbers...I guess I'll just get them off my car...seems logical

mbdoc · #7 10-05-2004, 08:11 AM

The W201 chassis (190's) has a unique A/C system!
Almost always when you hear a clicking from the right side of dash you have a problem with the "feed-back potientiometer" that sits on the blend air door.
When the potientiometer gets a bad spot it sends back BAD info to the pushbutton & the pushbutton cycles the switch-over valve on & off very quickly!

HAVE replaced at least 100 for that problem, dash must come out for replacement, however you can remove glovebox & plug in a new one to see if that is the problem. MB part number 201-821-02-60. Good luck