C250 TurboDiesel Sports '99 (T)

[ninja]

the heater in my C250 is not working properly. Sometimes it doesn't come on at all, then all of a sudden it will just start working. Thats not all, it mainly stays hot when it does work. When it isn't working, if I turn it to full power I get a small amount of cold air then at totally random intervals, it will blast out full power (only if switched to number 5). I have independant controls and have read the threads about the duovalve but I'm not sure how or where to start!

 

[Ian Brown]

probably the duo valve that is causing it to run hot all the time

 

[jberks]

The duovalve controls the heat, true, but it doesn't affect the fan.
The fan is controlled by the switch and then a regulator, before power is delivered to the fan. Regulators can do pretty much anything when faulty but are pretty easy to test. I'm not sure where they are on the 202 (above the passenger footwell on a 210 if thats any help) and with a muti meter you can see the different switch voltages coming from the control knob and measure the respective outputs to the fan.
It seems odd that you have 2 faults so I am also wondering whether there is an electrical fault that could account for both problems. Did both issues start at the same time?

 

[ninja]

W202 Heater/Fan?

Thanks for that, I am off to buy a multimeter and do some testing (should be fun!!) I will let you know where the regulator is if I found it :???:

The Fan\Heat thing has been happening for about six months and the lights have just recently gone.

I have been toying with the idea of giving it to a dealer to get the once over. Its a little past the service date and it can't do any harm to have it diagnosed (can it!?)

Thanks for the pic, can the duovalve be repaired or is new one required? nay idea how much? Same with the regulator, can it be repaired or will I need a new one?

 

[Ian Brown]

These are prices from euro car parts Duo Valve £78.75 Heater motor £97.13
Below is some pictures of the duo valve being stripped [I would buy a new one]
if its found to be faulty

 

[television]

There is a lot more in this than mentioned so far, you have sensors, inside and out. you have a pneunmatic circuit, venterlation sensors, valves for fresh /recirculate, plus 2 regulators and lots more,there is a counter bearing flap that can give problems. I could fill this page with it all.

Malcolm

 

[ninja]

Thanks guys, really helpfull. I think its off to the Merc dealer! At least I know what to expect. Thanks again.

Can someone give me an idea how much to ask for it in a private sale. Lets assume everything is fixed and its in immaculate condition throughout. Full black leather, Full Sport Spec, Sat Nav + loads more? oh, 130k miles, runs like an absolute dream...

 

[jberks]

Do yourself a favour. DONT go to the dealer!!!
Find a decent specialist. The dealer will charge you more than the car is worth and probably not manage to fix it!
I sat in reception last week and listened to a guy telling a customer about how the head needed to come off of his mid 90's S class and ..... - estimated bill starting at £1200 before parts. How anyone pays a dealer to do extensive repairs is beyond me. A fool and his money etc. Sure you can debate service cost against FMBSH and as mine is under warranty I don't care yet anyway, but when my last E started to run very badly, I was too scared top go into the dealer so I drove straight past the dealers door and on to the local specialist who sorted it for a fraction of what the dealer would have asked for and had it back to me the following day.
Remember, a dealer won't open the bonnet for less than £100!
As I am on my 3rd Merc I can now say with absolute certainty, Dealer FMBSH isn't worth a penny. I told the salesman that my last service was at the local specialist and waited for the "so it hasn't got FMBSH then - that will affect its value I'm afraid". Instead I got, "Merc-Care? - oh, thats fine."!!

 

[Suki]

Hi,
I had a similar problem, where my fan would not operate and/or operate slowly.
I manged to trace the problem to the fan.
The bushes in the motor had worn down.
A new fan is quite expensive, but a chat with a couple of people pointed me towards a company that manufactures carbon brushes for £5.
(If you can't get the brushes I would suggest using washing machine ones! I am sure this would work too!)
Regards
Suki

 

[Wezzel]

I had problems with an intermittant fan. It didn't matter what level the fan was set on but when I touched the switch it would randomly jump from level 1 through 5.

I took the switch assembly out and cracked the unit open. I then squirted contact cleaner into the switch unit and cranked it back and forwards a few times.

That was just over a year ago and it is still working okay.

 

[television]

I had problems with an intermittant fan. It didn't matter what level the fan was set on but when I touched the switch it would randomly jump from level 1 through 5.

I took the switch assembly out and cracked the unit open. I then squirted contact cleaner into the switch unit and cranked it back and forwards a few times.

That was just over a year ago and it is still working okay.

I am so pleased that you used contact cleaner and not WD40 in the control unit.

Malcolm

 

[ninja]

Darn Heat C250 TD Sport

how does the switch unit come out? That sounds similar to my problem, I wouldn't mind giving it a go.

I am going to do some investigations this weekend, I'll post the results. :-?

 

[Wezzel]

remove the radio.

Undo the two screws under the radio (at the top of the storage hole).

pull the two knobs off the heater and blower switches (make a note of which way the knobs are pointing).

The trim panel, with the switches, should then pull off.

If I remember correctly, there are a couple of screws holding the heater switch assembly in place.

Pull out the switch assembly and disconnect the multiplug.

Take the whole thing indoors and carefully separate the switch housing by sticking a screwdriver in the locking tabs one by one.

Spray the little round switch thingy (technical term - you probably won't understand) with contact cleaner and give the knobs a good twiddle back and forth.

Re-assembly (as they say in the manuals) is the reverse of dismantling.

It is a bit fiddly getting the heater rods back into the switch housing when replacing but if you put your hand up through the radio aperture it can be done without too much trouble. Just make sure the knobs are facing the same direction when you put them back

 

[dogsbody]

C250 Turbodiesel Sports '99T

If you resort to multimeter, do not be fooled by 12 volt readings on it!
Have had several problems over the years, specially with heater fans... they may indicate 12 volt, but will stop working if they cant draw enough amps - typical that they work on low speed but not on higher speeds. Normally cleaning either the contacts ( as suggested in the thread) or the actual spade conectors etc solves the problem. Dont forget the earth connection!

 

[television]

If you resort to multimeter, do not be fooled by 12 volt readings on it!
Have had several problems over the years, specially with heater fans... they may indicate 12 volt, but will stop working if they cant draw enough amps - typical that they work on low speed but not on higher speeds. Normally cleaning either the contacts ( as suggested in the thread) or the actual spade conectors etc solves the problem. Dont forget the earth connection!

Late models 1998 on, when there is a fault in the control unit the fan reverts to 5v slow speed, cleaning the contacts in the control module is a well know fault cure, providing the fan is running. On the default setting.if the fan does not run at all,check fan,if runs on 5v control module could be at fault

Malcolm