W210 - 1999 (T) - Continued Heater Temperature Control Problems....

rjsdavis · 22-04-2007, 12:53 PM

Hi there all

I've had continued heater problem with my W210 - I've replaced most things that I can think of, and can't see where to go with it next....

In short, my car "used" to have problems with the fan speed, insofar that the fan would not be properly controlled by the settings on the left-hand dial. A hefty slap on the dashboard sorted this out - but I also had problems with the actual temperature of the air coming out of the vents as well, insofar that this was ALWAYS hot no matter what setting the the temp control guages were on. Also - the fan used to come on all by itself after about 45-50 mins of motorway driving.

Anyway - the fan controls have been cured because I have now installed a new heater control panel in the dashboard - there are no problems with the fan speed or it coming on by itself.

HOWEVER - I do still have the temperature problems - and this hasn't changed at all. One fixed - HOT - temperature that comes out of the vents no matter what setting they are on.

Before you suggest it, I have also replaced the duovalve as well - and this has made no difference at all.

I now don't know where to go with it - I've changed what I thought were the obvious items - and have run out of ideas!

I should also add, that my car used to have very significant electrical problems which turned out to the voltage regulator on the alternator. This was replaced, and these have all gone - it was things like windows that would stop working, cruise control that would sporadically stop working, regularly blowing bulbs etc etc - these have ALL gone - but I am wondering if a component of the heating system could have been damaged (apart from the main control panel and duovalve), that I haven't thought of.... Any ideas out there??? Any assistance would be very much appreciated.

BlackC55 · 22-04-2007, 09:37 PM

You may find that one of the heater/aircon sensors may be faulty. A good diagnostic test should show this up. The values for the system need to be evaluated properly.

OR the heater control flaps are causing the problem. You may have one that is stuck causing your problem. A test with a star should find your problem if the user knows what he is doing.

rjsdavis · 29-04-2007, 09:59 PM

Quote:

Originally Posted by BlackC55

You may find that one of the heater/aircon sensors may be faulty. A good diagnostic test should show this up. The values for the system need to be evaluated properly.

OR the heater control flaps are causing the problem. You may have one that is stuck causing your problem. A test with a star should find your problem if the user knows what he is doing.

I shall try to get it onto a DAS machine asap - I don't suppose anyone knows a helpful garage / mechanic in the London / Kent area, that wouldn't charge the earth for quickly linking up their STAR machine do they?

Thanks for the reply.

rjsdavis · 10-09-2007, 05:28 PM

Quote:

Originally Posted by BlackC55

You may find that one of the heater/aircon sensors may be faulty. A good diagnostic test should show this up. The values for the system need to be evaluated properly.

OR the heater control flaps are causing the problem. You may have one that is stuck causing your problem. A test with a star should find your problem if the user knows what he is doing.

The car was recently taken into an air-conditioning specialist, who linked up an aftermarket computer, and went through the stored and current faults.

He cleared a number of faults, including one, which was talking about a communication problem between the heater control panel and a relay.
He also spent some time tapping the duovalve with a mallet. At the time, it appeared to be unresolved, as all during this time, the car was running, and the air didn't get any cooler.

On the journey home, I left the heater off, as I didn't want the hot air getting into the cabin and stiffling me! A couple of days later, I had to demist the screen, and had left the heater on for a while - it occured to me after a while that the cabin wasn't getting hot as usual, and I let the air into the cabin via the face-directed dash vents, AND IT WAS COOL! I couldn't believe it, and I nearly steered off the road in shock!

The air-con guy was the last person to do anything with it, so I am still none the wiser as to whether it was an ECU problem that he cleared, or as simple as beating the duovavle with a mallet - but the end is all I care about at the moment - I just need to refill the refridgerant back into the air-con system, and I will get some nice cool air - just in time for winter!

Dieselman · 10-09-2007, 05:31 PM

I'd go for the gentle manipulation of the duo valve being the fix.

I wonder if there is a correlation between cars not having the antifreeze changed and sticking duo valves?

jaymanek · 10-09-2007, 05:49 PM

Duo Valve.... simple as...

they stick and they often need a clean out... i must clean out one duo valve a month...

22-04-2007, 12:53 PM	#1
rjsdavis New Member Join Date: Sep 2006 Posts: 3	W210 - 1999 (T) - Continued Heater Temperature Control Problems.... Hi there all I've had continued heater problem with my W210 - I've replaced most things that I can think of, and can't see where to go with it next.... In short, my car "used" to have problems with the fan speed, insofar that the fan would not be properly controlled by the settings on the left-hand dial. A hefty slap on the dashboard sorted this out - but I also had problems with the actual temperature of the air coming out of the vents as well, insofar that this was ALWAYS hot no matter what setting the the temp control guages were on. Also - the fan used to come on all by itself after about 45-50 mins of motorway driving. Anyway - the fan controls have been cured because I have now installed a new heater control panel in the dashboard - there are no problems with the fan speed or it coming on by itself. HOWEVER - I do still have the temperature problems - and this hasn't changed at all. One fixed - HOT - temperature that comes out of the vents no matter what setting they are on. Before you suggest it, I have also replaced the duovalve as well - and this has made no difference at all. I now don't know where to go with it - I've changed what I thought were the obvious items - and have run out of ideas! I should also add, that my car used to have very significant electrical problems which turned out to the voltage regulator on the alternator. This was replaced, and these have all gone - it was things like windows that would stop working, cruise control that would sporadically stop working, regularly blowing bulbs etc etc - these have ALL gone - but I am wondering if a component of the heating system could have been damaged (apart from the main control panel and duovalve), that I haven't thought of.... Any ideas out there??? Any assistance would be very much appreciated.

22-04-2007, 09:37 PM	#2
BlackC55 Hardcore MB Enthusiast Join Date: Feb 2007 Location: Horndean, Portsmouth, Hampshire, Southsea Car: C43 AMG with mods, ML270, Mk1 Golf cab. Mk1 Caddy fully restored 7.5T truck Rotax Max race Kart ETC Posts: 8,251	You may find that one of the heater/aircon sensors may be faulty. A good diagnostic test should show this up. The values for the system need to be evaluated properly. OR the heater control flaps are causing the problem. You may have one that is stuck causing your problem. A test with a star should find your problem if the user knows what he is doing. __________________ Prestige car Service: I am listed here on MBClub please click to see services and discounts available.

10-09-2007, 05:49 PM	#6
jaymanek Hardcore MB Enthusiast Join Date: Nov 2002 Location: Nuneaton Warwickshire Car: 560 SEC AMG Widebody, 560 SEC AMG, W124 500E, W123 280CE, W123 200, R107-500SL Posts: 10,005	Duo Valve.... simple as... they stick and they often need a clean out... i must clean out one duo valve a month... __________________ Mercland is listed here on MBClub please click to see services and discounts available. 1969 280SL Pagoda in Met Light Blue 1980 123-200 in Sahara Yellow 1985 123-280CE in Champagne 1988 500SL in Met Light Blue Now with Leather 1988 560SEC AMG in Midnight Blue 1989 560SEC AMG Widebody 1993 E500 Brabus in Silver with lots of toys! 1 of 29 UK Supplied Cars Gallery Link

10-09-2007, 05:31 PM	#5
Dieselman Hardcore MB Enthusiast Join Date: Jul 2003 Posts: 19,310	I'd go for the gentle manipulation of the duo valve being the fix. I wonder if there is a correlation between cars not having the antifreeze changed and sticking duo valves?

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