'89 300SE weird HEAT, HELLLPP!!! - Page 3 - PeachParts Mercedes-Benz Forum

stormyc88 · #31 02-05-2013, 07:05 PM

Do it. Its cheap and easy. And like I said before, even if that's not the actual problem, it might be like a tune-up for your climate control, making it work a little better

draglink · #32 02-05-2013, 07:41 PM

Quote:

Originally Posted by stormyc88

Do it. Its cheap and easy. And like I said before, even if that's not the actual problem, it might be like a tune-up for your climate control, making it work a little better

So I went and looked at mine again. I have the fan, it is attached to some foam. looks like 2 wires come out of foam....is the sensor in there?

stormyc88 · #33 02-05-2013, 08:13 PM

The one I'm referring to is the one in the roof, P/N A 126 830 14 72, number "86" in one of those illustrations whunter posted. Does the motor you're holding have a rubber tube attached to it, leading to the passenger side A-pillar? If so, there is no sensor in it, its just a motor. The sensor is in the roof next to the dome light. There is another sensor mounted on the heater box, just keep that in mind. I think it's for the outside temperature, though. not sure.

BENZSTER · #34 02-05-2013, 09:20 PM

If I remember correctly, there is a small plastic filter basket within the mono valve housing. I believe you have to remove the mono valve to look down inside to see it. I'm thinking If you flushed your coolant system recently (recent radiator replacement) this filter may have enough sediment build up to cause your issue.

draglink · #35 02-06-2013, 06:51 AM

Quote:

Originally Posted by stormyc88

The one I'm referring to is the one in the roof, P/N A 126 830 14 72, number "86" in one of those illustrations whunter posted. Does the motor you're holding have a rubber tube attached to it, leading to the passenger side A-pillar? If so, there is no sensor in it, its just a motor. The sensor is in the roof next to the dome light. There is another sensor mounted on the heater box, just keep that in mind. I think it's for the outside temperature, though. not sure.

Thanks! yep that makes more sense...I saw that part, but couldnt figure out where it is!

draglink · #36 02-06-2013, 06:54 AM

Quote:

Originally Posted by BENZSTER

If I remember correctly, there is a small plastic filter basket within the mono valve housing. I believe you have to remove the mono valve to look down inside to see it. I'm thinking If you flushed your coolant system recently (recent radiator replacement) this filter may have enough sediment build up to cause your issue.

I didnt realize that. I have installed new thermostat and radiator and flushed the heater core. I have constant heat with the 'modified' monovalve I installed. When the new CCU arrives and I install the correct monovalve I will check for that screen in there...good tip, THANKS!!

pmckechnie · #37 02-06-2013, 07:49 AM

Slow down a little. You had said earlier that you still didn't have heat with the monovalve disconnected. The ccu can only turn the monovalve on or off. If it is unhooked, it is off. Off = heat. You now have heat with the modified valve, so that means the valve is bad. You can put in a new ccu if you like but I don't think you need it. Never replace parts until you prove they are bad. You have proved the valve is/was bad. The new ccu may not be as good as the one in there now. Fix/replace the valve and go from there.

Paul

draglink · #38 02-06-2013, 08:52 AM

Quote:

Originally Posted by pmckechnie

Slow down a little. You had said earlier that you still didn't have heat with the monovalve disconnected. The ccu can only turn the monovalve on or off. If it is unhooked, it is off. Off = heat. You now have heat with the modified valve, so that means the valve is bad. You can put in a new ccu if you like but I don't think you need it. Never replace parts until you prove they are bad. You have proved the valve is/was bad. The new ccu may not be as good as the one in there now. Fix/replace the valve and go from there.

Paul

Hey Paul,

I have replaced the monovalve twice. This last time there was nothing with the valve but at $15 for the new valve I figured it was worth a shot. It did not fix the problem. Now with the modified valve in I have full heat, I believe the CCU is bad, tellinig the monovalve to close when it shouldnt. New CCu should be here by weeks end so I will let yall know. In the meantime I am enjoying full heat!!

draglink · #39 02-08-2013, 07:16 AM

Still full heat with the modified monovalve....drove nearly 200 miles yesterday comfortably!!

New CCU came in yesterday, hope to install that and new monovalve this afternoon, will report back....

draglink · #40 02-11-2013, 06:10 PM

UPDATE: I followed a suggestion by Paul, just to rule out one thing at a time -thanks!

I first replaced the monovalve itself....same condition - little heat on start/warm up, then gone.

I then replaced the CCU and thought I had it solved. I drove around town all weekend and to my office with nice warm heat(local driving...rural roads under 45 mph or so). During work I had to make a few 20 mile interstate trips. As soon as I reach around 60+ mph, the heat diappears again!!

I have 'burped' the coolant system so I dont think there is an air pocket. I'm thinking now some debris or blockage that is restricting my water flow at a higher speed?? Are there any other moving parts in the monovalve housing that could fail? Some one had mentioned a screen in there but I dont see anything. Iam at the point this weekend of taking apart that secondary firewall and taking every hose etc off and inspect....also the whole monovalve assembly. Anybody have any other suggestions??

stormyc88 · #41 02-11-2013, 08:24 PM

Wire the valve so you can run it yourself LOL. Dam dude this is weird! I don't know if this makes a difference, but did you ever replace the ENTIRE monovalve with a new one? It's just a thought, but if you've only replaced the plunger assembly then the electrical connections are still old. Maybe there's a chance something's wrong with that part of it?

I know my heat used to do weird stuff (weak at idle, random full heat only, random no heat, too cold for the setting I chose, etc.) I did an overhaul on the heater side of the climate control to include: the aux. water pump, the monovalve, the overhead temp sensor, and the pushbutton unit itself. I did all of this with BRAND NEW PARTS. More costly, yes, but I'm one of those people that doesn't do used parts. I like fresh stuff, especially when it comes to plastic, rubber, and electronics/electrical, because I'm convinced that stuff gets lazy and brittle over the years. Let me tell you, it works like a champ now!

draglink · #42 02-12-2013, 06:53 AM

Quote:

Originally Posted by stormyc88

Wire the valve so you can run it yourself LOL. Dam dude this is weird! I don't know if this makes a difference, but did you ever replace the ENTIRE monovalve with a new one? It's just a thought, but if you've only replaced the plunger assembly then the electrical connections are still old. Maybe there's a chance something's wrong with that part of it?

I know my heat used to do weird stuff (weak at idle, random full heat only, random no heat, too cold for the setting I chose, etc.) I did an overhaul on the heater side of the climate control to include: the aux. water pump, the monovalve, the overhead temp sensor, and the pushbutton unit itself. I did all of this with BRAND NEW PARTS. More costly, yes, but I'm one of those people that doesn't do used parts. I like fresh stuff, especially when it comes to plastic, rubber, and electronics/electrical, because I'm convinced that stuff gets lazy and brittle over the years. Let me tell you, it works like a champ now!

No I have only replaced the plunger. I will look for a whole unit...I was thinking the same thing...

Its just really strange that with the 'modified' plunger I get full heat no matter what. That would kinda blow my theory of debris or something hindering the flow when up to speed....

stormyc88 · #43 02-12-2013, 02:08 PM

If it happens at almost exactly the same time every time you drive, when you reach highway speed, then I don't think it's air or debris. If it were, I would think that your loss of heat would be very random, and it would come and go, not just go and never come back.

draglink · #44 02-12-2013, 02:19 PM

Yes its pretty much the same thing everytime since I replaced CCU. Heat idle or in traffic, turns luke warm at best when 60 mph plus. When stop at a light the warmth will return.

I have the monovalve piston portion out now and see a check ball down in the bottom.....what does that do?

draglink · #45 02-12-2013, 02:39 PM

Here is an out of the box question. If I wired the monovalve directly to a switch, would I still be about to adjust the temp of air with the wheel, or would I have just full hot or full cold?

I know I would turn power off for heat, then switch on for cool air and AC