[TazMan1]

Hey All,

I'm having an issue with my 85 300sd where the blower shuts off if you move the temp control past min. It will blow if it is on min but nothing past that. Defroster won't blow either. I can feel heat coming out. I was thinking maybe monoclave valve but wanted to see if anyone had any other ideas. Checked and replaced the fuses. I can get it to come on randomly once in a while but Sunday night it stopped working again. Any ideas are appreciated.

Thanks

 

[et7724]

probably the pushbutton unit. i would check the in-cabin temp sensor first, but i think if its inop it would blow heat all the time if not in the min setting. testing is easy with an ohmeter

 

[tshoobs]

Did you ever resolve this? I have the exact same issue. It tends to come and go, has a mind of it's own. The temperature still changes but the only air you get is fresh air, which works overall but doesn't have the same affect as the actual blower.

 

[Rmac58]

As mentioned in post #2, the usual culprit is the push button unit itself.

You'll need to remove it, pull the cover and check for cold solders.

 

[RNT]

Check mono valve, pushbutton unit and unplug the auxiliary water pump. The plug is in plain sight between the battery and mono valve. You may have a faulty aux water pump.

http://www.benzworld.org/forums/w12...-burning-up-your-pride.html?highlight=burning

 

[zombiehunter]

As mentioned in post #2, the usual culprit is the push button unit itself.

You'll need to remove it, pull the cover and check for cold solders.

What's the fix for this? Resolder?

 

[Rmac58]

^ Yes, reflow or add solder as needed.

I'm pretty heavy handed, as you can tell.

 

[tshoobs]

Guess mine is coming out for sure, it's also stuck on half defrost, half vent all the time. Hopefully for the same reason.

 

[mclare]

Check mono valve, pushbutton unit and unplug the auxiliary water pump. The plug is in plain sight between the battery and mono valve. You may have a faulty aux water pump.

http://www.benzworld.org/forums/w12...-burning-up-your-pride.html?highlight=burning

It's not the PBU or Aux pump. 99% it's the PBU.

I have replacements if needed.