Heat finally works!!! Horray! - PeachParts Mercedes-Benz Forum

pawoSD · #1 12-17-2007, 01:11 AM

I replaced my thermostat tonight, and it went smoothly, all bolts came out without a single problem, unlike on my dad's SD, where two sheared off...

Then I began tackling the climate system. I removed the little piece of 2nd firewall, disconnected the hoses to the monovalve and aux pump, removed all the bolts holding in the aux pump and monovalve, and pulled the whole assembly out. (aux pump + monovalve) I got the pump separated from it, cut the plug off, stripped the ends of the wires and touched them straight to the battery. Nada. Not so much as a spark or a hum. Dead-er than dead. I took the pump apart and spun the motor, it didn't turn very easily by hand, tried power to it again, nothing. 100% shot. Got my replacement out of storage, tested it, spun right up smooth and quiet. So I installed everything back in, added a gallon of nice expensive MB coolant, and fired it up. After about 10 mins I was at operating temp of 83C! Yes! 7C higher than I used to hit even on the freeway! And the heat, the HEAT! I have nuclear power plant heat now in the car. Absolutely awesome. Well worth the efforts. I even did the fancy little 1A fuse holder splice onto the aux pump to protect the klima. So its all fixed and working now, and I don't have to freeze in my car anymore!

Tomorrow I am replacing my inside door handle, and shampooing/vacuuming the whole car out...and I will try to re-attach my wood trim on the glove box door. Never ending process!

KAdams4458 · #2 12-17-2007, 01:37 AM

Excellent work. Oh, how I long for an aux. pump that not only runs, but doesn't leak! Every one I have is either frozen solid and leak free, or runs well, but dribbles coolant all over the ground. I just can't win with these heating and cooling issues.

pawoSD · #3 12-17-2007, 01:39 AM

At least on the 300d you can see if it leaks....on the W126 its buried under hoses behind the engine, so if its leaking I won't know it.

At least not right away....

Hopefully it won't leak....that would stink....took me 3 hours to disassemble/reassemble that area. Way easier to replace on the 300D, its just chilling out in the engine bay in the wide open.

KAdams4458 · #4 12-17-2007, 01:58 AM

Very true. W123's seem to much easier to work in most aspects than the W126's I've looked at. I'd still be willing to accept taking on the responsibility of caring for, and feeding of one, though.

pawoSD · #5 12-17-2007, 02:09 AM

The W126 is well worth it. I know that replacing a starter on the W126 is easier than on a W123.....WAY easier.

Then again our W123 hasn't really needed much maintenance at all....no where near what our 126's have.

mobetta · #6 12-17-2007, 10:45 AM

excellent. I am always glad to see that peeps can get proper heat out of these.

I am still not impressed with the heat output of my 123. I put in a new thermo last week, and rebuilt the mono valve last fall. pump works great, i reckon(hear it hum away w/ key on) but still get luke warm air. thinking of bypassing the valve, and using blower fan speed to control the heat. in MN winters, that should be fine...

pawoSD · #7 12-17-2007, 12:56 PM

Quote:

Originally Posted by mobetta

excellent. I am always glad to see that peeps can get proper heat out of these.

I am still not impressed with the heat output of my 123. I put in a new thermo last week, and rebuilt the mono valve last fall. pump works great, i reckon(hear it hum away w/ key on) but still get luke warm air. thinking of bypassing the valve, and using blower fan speed to control the heat. in MN winters, that should be fine...

You must have a flow problem or a plugged heater core. Our 300D has MEGA heat....Super super mega.

Newguy · #8 12-18-2007, 11:34 AM

When did they start using the auxilary pump?
Would there be one in my 80 300SD W116? If so, is it part of the monovalve?

pawoSD · #9 12-18-2007, 11:37 AM

I don't believe your car has one. You have the older style "climate servo" setup....which is prone to problems (cracking and leaking mostly).

vstech · #10 12-18-2007, 11:44 AM

there should be a aux pump in addition to the climate servo... my older 123's have both.

pawoSD · #11 12-18-2007, 12:19 PM

Quote:

Originally Posted by vstech

there should be a aux pump in addition to the climate servo... my older 123's have both.

I couldn't get the EPCnet to open, so I had to make a guess.

I guess I was wrong.

#12 12-18-2007, 12:44 PM

Quote:

Originally Posted by mobetta

excellent. I am always glad to see that peeps can get proper heat out of these.

I am still not impressed with the heat output of my 123. I put in a new thermo last week, and rebuilt the mono valve last fall. pump works great, i reckon(hear it hum away w/ key on) but still get luke warm air. thinking of bypassing the valve, and using blower fan speed to control the heat. in MN winters, that should be fine...

A W123 should burn you out of the car! Like this:

Heater core might be plugged.

#13 12-18-2007, 12:47 PM

I agree, a W123 should make enough heat to melt your face if it's working correctly. If you are sure the monovavle is opening, try flushing the heater core (carefully).

mobetta · #14 12-18-2007, 03:39 PM

I did flush the core when I did the water pump last year- w/ a hose hooked to one end, the other open. It seemed to flow fine.

now back to your regular post.....

jtwangler · #15 11-13-2008, 10:56 PM

It seems that one of you guys might have some info for me.

I've searched the forum at length and haven't found anything that really gives me detailed information to get my heater working.

I have excellent ice cold a/c and just replaced the blower motor. My CCU only functions on "defrost" and when I scroll the wheel to hot it just continues to blow cold even with the a/c button flipped to off. I don't have the slits in the dash for a sensor. Not sure if an '80 300D is even equipped with one.

I haven't had to work on this at all yet since it's only now getting chilly in the desert at night. I've read about the "evil servo" and all (not sure if that is even part of my problem) but I really just want to know the easiest/best fix for this. Any detailed info regarding the troubleshooting steps for the heating system would be greatly appreciated.

Thanks!