I hav a 1983 300SD Turbo with only 202,000 KM in near mint condition. I had a new stereo installed by a audio shop and enjoy my new CD player but at the expense of my climate control. Maybe they damaged something in the wires or whatever when installing the new radio. What happens is that all the fans work but heat comes out for only about 1/2 minute and turns to cold right fast. If you stop the car, shut off the ignition switch then restart the car or just turn on ignition to accessary, the heat will again pour out again for another 30 seconds or so. then stop again

I guess that the valve that allows the hot water to go thru the heater core shuts off about 30 seconds after I start the car. It seems though that if I roll the dial to MAX the heat continues to blast out and doesn't turn cold. None of this has ever happened before. The no heat thing that is, as I just left it on 22 degrees and it always worked great until immediately after they put in the new CD player.
Does anyone have some ideas here, as the installer says he is insured but he wants to pull out the radio and have a look for a broken wire or something. I'm concerned they may have screwed up a module or something worth big bucks.

Over near the battery is the mono-water valve. Kind of square shaped if looking from the top, and a silver colored "button" on top, with 1 two-wire connector. Try removing that connector and see if you get full heat (uncontrollable by the heater controls at all), OR if it acts the same way. If you get uncontrollable max heat, you have a fairly involved problem, probably relating to the radio work.
If it acts the same way, there is a problem with the mono-water valve, but it probably just needs the repair kit.
Let me know the results of disconnecting the wire from the valve and I can tell you how to take apart and visually inspect the water valve interior, or use the search function, it's been discussed many time before.

Gilly

Thanks for your reply. I followed your test procedure and I got uncontollable maximum heat. Then I reconnected the wire and the heat quit again. I guess this means that I have as you say an "involved problem"? Do you think the possible damage done by the Radio installer can be resolved by them or is it now out of there realm?

I'd ask them to at least look at it, see if they think they attached some wiring to an incorrect wire, like maybe a temp sensor?
Really confusing how this would happen, as everything a typical system would need is available by just using the original radio wiring.

Gilly

So I took the car back to the radio shop and got nowhere. They said they couldn't fix it ,and it was unlikely to be caused by the radio installation. I know better, as it had always worked perfectly right up to the minute I left their shop. What it comes down to is that once the temp achieves the 22 degree setting the heat shuts off and blows only cold air and heat will not return until the ignition switch is shut off.
I found that if I slightly turn the switch towards the off position while the car is running it will reactivate the heat. The installer said he phoned the Mercedes dealer and the dealer said that installing a new radio could not effect the operation of the climate control. I don't beleive that story, as no shop in their right mind would defend this situation.
Kind of looks like I'm flogging a dead horse here, and will most likely have to try to resolve the problem myself.

OK, so you want me to run down what the different wires on the radio do or what? I would think that if you look at the original wiring on the RADIO side, and look at what they are attached to (colors of wires) then maybe you can spot something not correct.
For example if there is a red wire on the radio side, and they have it attached to a yellow wire for example, then that is incorrect. Can you remove the radio yourself, or need help?

Gilly

Radio stores are notorious for "fishing" for a hot lead and splicing into it whatever it goes to, and they are also very bad about just slamming things in and screwing it down tight without checking for pinched wires, etc.

It's entirely possible that they either broke something or pulled something loose while bashing around on the radio. They are obligated to take the car to a dealer or indie and get the CC fixed, they damaged it and "there's nothing wrong, we didnt' do it" won't cut it.

If the CC doesn't work, it's broken -- this really isn't a discussable item.

Most likely it's either a cut wire or pulled plug.

The dealer is right, installing a new MERCEDES radio won't affect the climate control, but what about a NON Mercedes hack job? All bets are off! I've got a real hack job to fix on the 280, the idiots cut the loom between the original Becker and the amplifier and "grabbed" a hot wire, leaving the rest bare. Used wire nuts to connect tiny wires to the factory speakes, rear only, etc.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I just got your latest reply as I had to go out of town. The sales guy in the store told me to take it to a reputable repair shop and they will pay for it . So I will give that a try first and see if this goes anywhere. In the meantime thanks for your advice. I will post the result back here in a few days.

I'm glad they 'fessed up to the possibility that they caused your heater malfunction. My Indy in Whidbey Island spent numerous hours and big bucks from the owner getting the climate control straightened out after a hack job by the radio installer, the bill ended up being something like US$1200! I don't know if that installer paid the bill or not.

Happy Motoring

RBM