No heat, what am I missing. Also check valve ques. - PeachParts Mercedes-Benz Forum

winmutt · #1 10-29-2006, 06:45 PM

I get to step2 of the FSM section 83-6002 (ye old acc testing) on me wifes wagon and no heat. I've checked everything, but I am clearly missing something where does the heat come from? I read in here that someone said that if the aux water heater pump is UNPLUGGED it should be full blast heat?

Also there are 3 one way check valves. I think I may have gotten them miscombulated while checking the vacuum system. I found one to be bad and replaced it but I think I may have all 3 of them in the wrong order. These are the yellow type with a fatter end with lip on one side. The one check valve in the middle of the console is current with fat end pointing left. The two under the glove compartment are fat end right. Is this correct? I should have taken a picture before I got started..................

Shorebilly · #2 10-30-2006, 07:21 AM

G'mornin',

Have you checked the monovalve??

As usual, the heating system is a tad more complicated than those in most autos.

You will not get heat ...IF....the engine has not warmed sufficiently.....there is a little temperature sensor someplace....

No heat if auxiliary pump does not work.....

No heat if monovalve needs a rebuild....

I have not had the pleasure of troubleshooting this system, just read the heating section of the Climate control system...awhile back.....publication was...MB Service Manual Heating and Air conditioning Automatic Climate Control Model 123

As I remember.....if the Engine temperature sensor is inoperative for whatever reason.....including disconnected or broken wiring......then there will never be a signal that tells the Climate Control that the engine is up to temperature....thus you will never get heat.....

I may be wrong, I am writing this from memory......I did not look this up....

SB

winmutt · #3 10-30-2006, 07:45 AM

Quote:

Originally Posted by Shorebilly

G'mornin',

Have you checked the monovalve??

As usual, the heating system is a tad more complicated than those in most autos.

You will not get heat ...IF....the engine has not warmed sufficiently.....there is a little temperature sensor someplace....

No heat if auxiliary pump does not work.....

No heat if monovalve needs a rebuild....

I have not had the pleasure of troubleshooting this system, just read the heating section of the Climate control system...awhile back.....publication was...MB Service Manual Heating and Air conditioning Automatic Climate Control Model 123

As I remember.....if the Engine temperature sensor is inoperative for whatever reason.....including disconnected or broken wiring......then there will never be a signal that tells the Climate Control that the engine is up to temperature....thus you will never get heat.....

I may be wrong, I am writing this from memory......I did not look this up....

SB

monovalve== regulator right? The temp sensor works fine. The acc doesnt turn on in heating mode until engine temp is @ 60. The aux water pump is getting juice. I checked the resistance on it and it was 1? I dont know if this is normal for motors or not. Also there was only power I didnt see a switched wire to it just + / -.

This I did notice. As stated one check valve was bad. Also the leg room flap actuator is completely shot... Other than that the vacuum system leaks a little but AC kicks on fan blows etc. Just no heat.

ImBroke · #4 10-30-2006, 08:16 AM

Quote:

Originally Posted by winmutt

I read in here that someone said that if the aux water heater pump is UNPLUGGED it should be full blast heat?

I should have taken a picture before I got started..................

If you disconnect the monovalve electrical connection, there should be full blast heat. Also, if you put it to defrost, there should be hot air coming out of the defrosters. Not sure about the vacuum part of it, I believe the vac parts only control where the air is flowing, the dial controls voltage to the monovalve, which controls how much heat you get. What you need to do is take a digital voltage meter, and hook it up to the connector to the monovalve, and rotate the dial. The voltage should change, from battery voltage at minimum to zero volts at maximum. Hope this helps.

winmutt · #5 10-30-2006, 09:13 AM

Quote:

Originally Posted by ImBroke

If you disconnect the monovalve electrical connection, there should be full blast heat. Also, if you put it to defrost, there should be hot air coming out of the defrosters. Not sure about the vacuum part of it, I believe the vac parts only control where the air is flowing, the dial controls voltage to the monovalve, which controls how much heat you get. What you need to do is take a digital voltage meter, and hook it up to the connector to the monovalve, and rotate the dial. The voltage should change, from battery voltage at minimum to zero volts at maximum. Hope this helps.

Rotate which dial? Take the regulator apart? monovalve == regulator?

ImBroke · #6 10-30-2006, 12:37 PM

Sorry for the confusion. Rotate the dial on the ACC, the one that goes from blue and min, then 18, 22, 26, red and max.

winmutt · #7 10-30-2006, 01:43 PM

No mono valve on mine. Mine is older PBC style.

ImBroke · #8 10-30-2006, 03:59 PM

Is this on the 83? If so, here's the monovalve. If it's not the 83, I'm not sure. If I posted something you already know, I'm sorry for stating the obvious.

winmutt · #9 10-30-2006, 05:29 PM

Quote:

Originally Posted by ImBroke

Is this on the 83? If so, here's the monovalve. If it's not the 83, I'm not sure. If I posted something you already know, I'm sorry for stating the obvious.

on the 80 wagon, aka wifes diaper wagon

ImBroke · #10 10-30-2006, 06:04 PM

Thanks for the clarification. I'll step aside now. Good luck!!

winmutt · #11 10-31-2006, 09:53 AM

Bump. Anyone? I am surely missing the most elementary portion of the ACC.

tobybul · #12 11-04-2006, 01:23 AM

Quote:

Originally Posted by ImBroke

Is this on the 83? If so, here's the monovalve. If it's not the 83, I'm not sure. If I posted something you already know, I'm sorry for stating the obvious.

Thanks for the pic. My 85 300D is not producing enough heat (air out of vents not hot anough). Plus, maybe vacuum problem too cuz cold air comes out of right side vents.

Should the engine be running when I chk for voltage at monovalve?

biopete · #13 11-04-2006, 02:47 AM

Quote:

Originally Posted by tobybul

Thanks for the pic. My 85 300D is not producing enough heat (air out of vents not hot anough). Plus, maybe vacuum problem too cuz cold air comes out of right side vents.

Should the engine be running when I chk for voltage at monovalve?

just make sure the heater / ac is on and blowing while you are playing with it

monovalves are supposed to fail open so you should get heat by simply unplugging it. If you dont, unscrew the 4 screws on top and pull it out and see if it is all clogged up. If that does not work, maybe the heater hose circuit is air locked. Prime it with a pump -- Sears, walmart, all have fluid transfer pumps for like 10.00. Unplug line connecting to "out" of heater core and hook up pump and suck until fluid is flowing good though the heater core system.

hth