w124 2.5T no heat what now ? - PeachParts Mercedes-Benz Forum

blk90s13 · #1 09-24-2012, 10:01 PM

I changed the blower motor last year it works fine since with no issues AC blows cold and all but now that its a little cooler in the morning I tried to put the heat on today and NO HEAT !

the middle vents does not blow ( I know they don't blow heat anyway ) and the sides blow COLD air and the compressor engages once any button on the climate control is pressed no matter the temp is set to cold or hot !

where should I start looking and for what

thanks all

sixto · #2 09-24-2012, 10:09 PM

The compressor will engage in any mode except OFF and EC.

Disconnect the low pressure switch (the one without pigtails) at the dryer behind the driver side headlight so the compressor doesn't engage. Removing just one wire will suffice. If the compressor engages, you have a problem with the Klima relay. If the compressor doesn't engage, set the control to defrost and feel for warm or hot air. If you get warm air at idle and tepid air at speed, your monovalve is likely at fault. IIRC the 124 monovalve doesn't have a replaceable cartridge like the 123 and 126 monovalve. I don't know if it can be rebuilt by mortals. If you still don't get heat, disconnect the power to the monovalve. This should leave the monovalve wide open for coolant flow to the heater core. Still no heat? That's a really unusual situation.

Sixto
87 300D

Jeremy5848 · #3 09-24-2012, 11:52 PM

The 124 monovalve may be rebuildable (note Sixto's caveat) but you have to come up with parts, which are unavailable new. You might be able to take several used monovalves and build a good one our of the pieces. "No heat" is unusual and suggests a clog somewhere preventing the flow of hot coolant. Check the aux coolant pump and the monovalve for blockages. You want to hope it's not the heater core as that requires pulling the dash, a time-consuming job although not the horror that it's made out to be since several have posted excellent DIY procedures here.

Jeremy

blk90s13 · #4 09-25-2012, 07:31 AM

Thanks, will get to it this afternoon and see how it goes.

engatwork · #5 09-25-2012, 08:01 AM

Inspect/check out the hoses and stuff in front of the battery. May need to pull out the volt meter and feel the various hoses to see if you can tell where the hot water is/isn't.

Chris W. · #6 09-25-2012, 01:02 PM

You know, about the monovalve. Back in the day I had a E28 535i, and the heater valve is reputedly the same as the monovalve for the 124 as the E28. BMW has part number 64 118 390 132, heater valve rebuild kit, which has the core of the BMW heater valve. Can see it here about 2/3 of the way down the page.

http://www.************/se1.asp?dept_id=98

OK that link got censored. It was from b a v auto.

I don't know if this actually fits, never seen it in black and white that it is a replacement for the MB part, only hearsay.

Strangely, XXXX has this part for $44.95, but XXXX shows the part as "valve" for $115. Maybe they have it as the whole valve.

But wait, Pelican parts has it for $15! Here: BMW E28 Heating - Page 1

That's almost cheap enough to risk buying it on the chance it will fit the 124. All I know is that it fixed no heat at high speeds on my old E28!

Rgds,
Chris W.
'95 E300D, 376K

blk90s13 · #7 09-25-2012, 11:09 PM

1 : Disconnect the low pressure switch (the one without pigtails) at the dryer behind the driver side headlight so the compressor doesn't engage Done and compressor stopped engaging

2 : set the control to defrost and feel for warm or hot air. If you get warm air at idle and tepid air at speed Yes that is what is happening

Disconnecting the power to the monovalve by taking both plugs off ? and just leaving them off ?

there is two hoses coming out the valve or one in and one out the one on the side (closer to battery )is HOT the one on the bottom is just COOL

I am thinking valve is stuck shut ? I will have to open it and try to clean it right ?

Mercedes-Benz: The Duovalve

engatwork · #8 09-26-2012, 08:10 AM

See if you have 12 volts to the duovalve with the car running.

Jeremy5848 · #9 09-26-2012, 11:02 AM

It's been many moons since I had a monovalve apart but that BMW part does look similar. Whether it is the correct size is another thing. Might be worth looking at some BMWs in the junkyard, see what their valve looks like.

Jeremy

compress ignite · #10 09-26-2012, 07:06 PM

0008350644 AC & Heater Control Valve; Mono Valve Solenoid Repair Kit 300D 380SL 300TD 560SL 560SEC 300CD 300SD SOME BMW

BUT the Monovalve it fits is BOSCH part # 1 147 213 007 WHICH Ain't the W124 Chassis Valve!

(W124 Monovalve is BOSCH 1 147 412 037 / Mercedes part # 000 830 72 84)

____________________________________________________________________________________________________ ______

Mercedes Part # 000 835 0644 is the repair kit for the Bosch # 1 147 213 007
Which is the BMW part #

Pelican Parts - Automotive Parts and Accessories - Porsche & BMW

____________________________________________________________________________________________________ ______

0008350644 AC & Heater Control Valve; Mono Valve Solenoid Repair Kit 300D 380SL 300TD 560SL 560SEC 300CD 300SD SOME BMW
Shows the Repair Kit fits:

blk90s13 · #11 10-04-2012, 10:17 PM

Quote:

Originally Posted by engatwork

See if you have 12 volts to the duovalve with the car running.

I get 13+ V with car running and once the climate control is turned on it drops down to .54

is that normal ?

sixto · #12 10-05-2012, 01:03 AM

Depends on the thermostat setting.

Sixto
87 300D

blk90s13 · #13 10-05-2012, 07:38 AM

Quote:

Originally Posted by sixto

Depends on the thermostat setting.

Sixto
87 300D

set to max heat

Zulfiqar · #14 10-05-2012, 10:47 AM

When I got my car the heat would not work, I gently tapped the valve with a very small hammer and it started working again.

I have seen a post on a UK forum where someone rebuilt their W124 heater valve with new parts - but cannot remember now.

sixto · #15 10-05-2012, 06:08 PM

Very low voltage in defrost (max heat) sounds right.

Sixto
87 300D