Heater Help Klima II - PeachParts Mercedes-Benz Forum

vwnate1 · #1 12-17-2015, 10:28 AM

I'm sure there are exhaustive previous threads so feel free to link them .

I'm getting no heat even when I unplug the Monovalve .

I have some basic Klima II questions :

When the temp. wheel is rolled to MAX. heat , does the little click at the end , turn on the electric auxiliary water pump ? .

Am I correct in thinking that unplugging the Monvalve's wire *should* provide heat in the ' EC ' mode regardless of temp. wheel position ? .

I've replaced everything in my car (1982 300CD) and am trying to figure out the proper testing regimine .

TIA ,

funola · #2 12-17-2015, 10:47 AM

No power to monovalve = full open = full heat. An easy way to diagnose heater problems is with your hands. From a cold start, as the coolant warms, feel the hose starting at the head (by the oil filter, which should be the first hose to get warm) then touch other hoses and feel what's happening.

Zacharias · #3 12-17-2015, 11:54 AM

Quote:

Originally Posted by vwnate1

When the temp. wheel is rolled to MAX. heat , does the little click at the end , turn on the electric auxiliary water pump ?

Not as I recall (from at one time reading a functional description of the system).

The MAX setting disables the temperature regulation and is supposed to provide maximum heat. Is. Supposed. To.

I am also having monovalve headaches and this was not happening when I selected MAX. I replaced the PBU and temperature selector wheel on the weekend and now when my system temperature regulation dies (in the case of my 300d, after a hot restart) I can get heat when I turn the wheel to MAX. But it is far from "maximum" heat.

My issue is that I lose heat for a while after a hot restart, and also at highway speeds.

resto108 · #4 12-17-2015, 01:00 PM

In the service manual, there is a complete test procedure for the different types of climate control systems. It tells you what every component should be doing at all the different systems. Look around task 83-600 in the Climate Control Manual.

vwnate1 · #5 12-18-2015, 10:59 AM

THANK YOU for all the replies ! .

I'm not sure what the ' PBU ' (? Push Button Unit ?) is , I have a rebuilt one but the temp. wheel has always been very stiff on it .

I'll have to go looking for my FSM and see if I can find the testing chapter .

At the moment I'm driving my '84 Euro Spec. 300TD , it has Kilma II and heat so we're good to go but I really want my Coupe to have heat too .

As long as we're here , what is the current suggested Coolant choice ? .

I *think* it was Zerex a few years back , at the moment I'm using Honda typ pre mix coolant as it's O.K. on the alloy parts .

But , I also do a change and flush every two years in January so if i should swap to one of those yellow coolants , I will .

vwnate1 · #6 12-18-2015, 11:04 AM

Quote:

Originally Posted by funola

No power to monovalve = full open = full heat. An easy way to diagnose heater problems is with your hands. From a cold start, as the coolant warms, feel the hose starting at the head (by the oil filter, which should be the first hose to get warm) then touch other hoses and feel what's happening.

Are you quite sure that's the correct coolant flow ? .

Many InLine engines tap the heater from the front , part of the by-pass system so when the T-Stat is closed it forced more coolant to the heater....

The auxiliary electric coolant pump is plumbed into the front hose so that's why I thought the coolant flows from the front to the heater then returns to the rear left of the cylinder head....

Zacharias · #7 12-18-2015, 11:29 AM

Quote:

Originally Posted by vwnate1

.I'm not sure what the ' PBU ' (? Push Button Unit ?) is , I have a rebuilt one but the temp. wheel has always been very stiff on it .

Yes, sorry I used the short form, I mean the control panel on the dash. Funny, the panel I just installed (purchased lightly used from another forum member) is also rebuilt, and the temp wheel is really really stiff on mine as well.

Quote:

Originally Posted by vwnate1

As long as we're here , what is the current suggested Coolant choice ? .

The Japanese-spec mix is better than Prestone-type yellow, but ideally Xerex-G5 or the Mercedes factory type.

If you are changing and flushing every two years, that is serious overkill. But if it makes you happy....

vwnate1 · #8 12-18-2015, 11:47 AM

Thanx for the reply .

I have always had terrible problems with water cooled vehicles , maybe because I buy from Junk yards or ' end of life ' vehicles then return them to the road so I'm skittish about neglecting cooling system service .

You should see the 1/8" of goop I laboriously cleaned out of the SLS tank yesterday , some boob had put in ATF

.

I know I'll be doing multiple Hydralik Fluid changes for a a while yet until it remains clear.....

Good to know the temp. wheel is supposed to be stiff , when these cars were new I only drove them in and out of the Service Bays and never touched the HVAC .

Is the temp. wheel available new separately ? .

Please keep the comments , suggestions and death threats (

) coming , they're all very useful .

I'm off to pick up my tools and get to work .

OBTW : I stopped my my Mercedes Dealer to buy two more quarts of SLS Hydralik Fluid and saw the M-B branded coolant , he says it's $ 34.95 the gallon ! gasp .

Zacharias · #9 12-18-2015, 11:52 AM

I didn't meant that the wheel is supposed to be stiff (mine requires huge effort to turn in the 22-26 degree range), just that mine is also a rebuilt and has that issue. Every w123 or w126 with that panel that I have driven was different, but all were much easier to turn.

I know that on the older ACC (vertical pushbuttons) the temp wheel was a separate part, and I suspect it is on these control panels as well, but someone else will have to confirm.

funola · #10 12-18-2015, 12:00 PM

The rotary temp dial and switch consists of a potentiometer and a switch at the the end of clockwise rotation. The switch consists of a wiper and p.c. board traces which can be taken apart and cleaned with a pencil eraser. The wiper can be re-bent to restore contact tension. Do not lose the detent ball when you take the switch apart (do it while in a clear plastic bag). Lube it with some Vaseline before re-assembly to slow the oxidation.

vwnate1 · #11 12-21-2015, 03:01 PM

Thanx .

What is the purpose of the switch ? .

funola · #12 12-21-2015, 04:18 PM

Quote:

Originally Posted by vwnate1

Thanx .

What is the purpose of the switch ? .

Gives max heat.

dude99 · #13 12-21-2015, 06:47 PM

Quote:

Quote:
Originally Posted by vwnate1
Thanx .

What is the purpose of the switch ? .
Gives max heat.

Gives max heat if the potentiometer fails, sort of a fail safe.

vwnate1 · #14 12-22-2015, 09:27 PM

I'm not sure if you're pulling my leg or what here .

HOW does it give max. heat if not by cutting power to the Monovalve ? .

funola · #15 12-23-2015, 11:01 AM

Quote:

Originally Posted by vwnate1

I'm not sure if you're pulling my leg or what here .

HOW does it give max. heat if not by cutting power to the Monovalve ? .

I don't think anyone is pulling your leg. Did anyone say it does not give max heat by cutting power to the monovalve?

You say you have Klima II. The different ACC systems for W123 are I, II and III. You sure your 82 CD is II? Maybe you should post up a pic of your system?