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  #1  
Old 02-08-2006, 01:38 PM
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Help a homie's heater Not the monovalve

Heat is sporadic at best, normally just cold.

I assumed it was the monovalve and replaced it using the ebay rebuild kit for no good reason, the diaphram was fine.

After hours on the forum and alot of thinking I'm suspecting the auxilary pump or the heater core is clogged.

What I'd like help with:

Testing the Pump
Would it be possible to test the auxilary pump with some leads and the battery? Is the connection accessible without alot of dissasembly? If I'm able to give it 12 volts will I be able to hear it run?

Testing the Monovalve
How do I check the monovalve solenoid operation? The connector to it was messed up and I'd like to make sure the wiring is correct. When should it have voltage?

I will feel some heat if I "get on it" high RPMs, but not alot of heat. Which worries me the core is clogged but I've felt hot air within the past month. I recently changed the thermostat and the coolant was nasty.

The engine is reaching operating temperature and staying there.

Sorry for getting back into a thread thats been discussed a bunch before but I didn't see these questions addressed when I did my searches.

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  #2  
Old 02-08-2006, 01:50 PM
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Did you read this post? Yet another Climate Control issue...
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  #3  
Old 02-08-2006, 01:54 PM
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Quote:
Originally Posted by goosebahr
What I'd like help with:

Testing the Pump
Would it be possible to test the auxilary pump with some leads and the battery? Is the connection accessible without alot of dissasembly? If I'm able to give it 12 volts will I be able to hear it run?

Testing the Monovalve
How do I check the monovalve solenoid operation? The connector to it was messed up and I'd like to make sure the wiring is correct. When should it have voltage?
Yes, you can certainly test the pump with a set of 12V leads. The connections is easily accessible on the W123. You'll hear or feel it run. If it does not run, there is a good possibility that it has fried your CCU and then all kinds of strange things will occur. In my case, the blower failed to operate at any speeds. Note, however, that the lack of heat at higher rpm's pretty much rules out the pump as the primary cause of the problem. You should check the operation of the pump in any case. If the pump does not operate, do not plug it back into the connector.

If the diaphragm is intact, the monovalve defaults in an open condition. So, your lack of heat is not related to the monovalve.

The fact that the cooling system has not been maintained strongly suggests that the heater core is partially blocked. You can disconnect the hoses to and from the heater core and rig up a garden hose to force pressurized water through the core in an attempt to unclog it. Be very careful with this process because the core is not designed to handle line pressure (70 psi). It will suffer this pressure if it is partially or almost completely blocked.

You'll probably need to do a citric acid flush of the entire system in an attempt to cure the problem. Otherwise the core must be removed. This is not a pleasant task.
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Old 02-08-2006, 02:19 PM
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Thanks for the quick replies

I must have missed the "yet another climate control" thread, I promise I've been investigating all morning. Good Info I will check out later today.

I'm driving/working on a 126 I know the pump is hidden between the firewalls but is the wiring accessible without alot of dismantling?

I'm looking forward to cleaning out the heater core I'd love to see a handful of goo blow out the other side.
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  #5  
Old 02-08-2006, 02:45 PM
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Quote:
Originally Posted by goosebahr

I'm driving/working on a 126 I know the pump is hidden between the firewalls but is the wiring accessible without alot of dismantling?
The pump is definitely down low between the firewalls. You'll need to take out the section of the forward firewall and disconnect some hoses to get your hand on it to see if it is running. The plug is accessible near the top of the firewall close to the battery.

The battery needs to come out as well.

Not as simple as a W123.
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  #6  
Old 02-08-2006, 07:05 PM
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Thumbs up Weird Fix!

The problem with my heating was me being a cheap ass.

I recently replaced the heater core hose from the engine to the heater core, to save a few bucks I bought the hose without the heated windshield option.

It finally got cold and I started to worry about my heat. Replaced the monovalve and figured it had to be a plugged heater core. I flushed out my cooling system and saw a fair amount of trash but nothing huge.

Heat worked for a little while then returned to cold air and would heat up with RPM's.

I looked some more and found the return line for the heated windshield, thought it was a long shot but I plugged it and now my heat works again!

Good info if you guys replace that hose with a non heated windshield one.
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Old 02-08-2006, 08:38 PM
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Quote:
Originally Posted by goosebahr
I looked some more and found the return line for the heated windshield, thought it was a long shot but I plugged it and now my heat works again!

Good info if you guys replace that hose with a non heated windshield one.
I'm completly lost by this.

Can you explain from the beginning regarding the return line for the heated windshield?? What return line? What heated windshield??
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  #8  
Old 02-09-2006, 11:03 AM
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Heated Windshield Wiper Headrest

I never heard of it or knew it existed until my hose started leaking. Its an option to heat your windshield wipers.

The hose that feeds the heater core has a T in it where a piece of 3/8 or so hose feeds a heater(????) for the windshield wipers a return line for the windshield wiper heater goes right into the monovalve assembly.

Sorry I was refering to it as a heated windshield. When I removed the return line and plugged it my heat started working again. Pulling a vaccum, air etc??

Hope I made it a little clearer this time.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1K60UC4F81QA0N8Y15&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=R3030-16734&application=000027714

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1K60UC4F81QA0N8Y15&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=R3030-16731&application=000027713
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Old 02-09-2006, 11:16 AM
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Thumbs up I am interested in this option..........

I have never seen a w126 with a wiper heat rest. Does anyone currently have this option. Photos??
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  #10  
Old 02-09-2006, 11:37 AM
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Quote:
Originally Posted by SD Blue
I have never seen a w126 with a wiper heat rest. Does anyone currently have this option. Photos??
I do. It's a little heat exchanger bonded to the bottom of the windshield. To tell the truth, I don't know if it does anything or not.
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  #11  
Old 02-09-2006, 11:41 AM
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Quote:
Originally Posted by SD Blue
I have never seen a w126 with a wiper heat rest. Does anyone currently have this option. Photos??
I've never seen it myself. The '84 does not have it. AFAIK, it was available in the models after '86.

Real interesting. Funny that it would be added as an option.

Anyone else have one of these??
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  #12  
Old 02-09-2006, 12:00 PM
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There is also a thermostat plumbed in series with the heater that is supposed to open at about 2-4C or below.

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