HVAC and Cruise Troubleshooting?
 

Looking for info on troubleshooting my hvac system (always blows hot, etc.), and my non functioning cruise control. Are there any good write-ups on this?

Thanks,

Mike

What car are we talking about here?

I know a guy for cruise... ;)
http://cruisecontrolrepair.com/

Sorry about that. I thought I had my signature setup. Its an 85 300d

Mike, what kind of problems are you having with your cruise?

It is not working at all

Most cruise problems stem from the amplifier. However you can perform some tests yourself to assess the rest of the cruise control system, the actuator and the inputs to the amplifier.

Here's my write up on diagnostics that includes links to test the things I mentioned above.
https://sites.google.com/site/mbcruisecontrolrepair/home/diagnostics

If you should pull your amplifier, it should be one of the following part numbers:
001 545 79 32
002 545 32 32
002 545 91 32

Excellent! I will check it out.

Did you ever figure out your HVAC problem? My '83 300CD only blows hot too.

Can you give us more information?

Any changes when you adjust the temp wheel?
Any changes when you select a different setting?
Any changes when you select a different blower speed? Speeds work?

Have you inspected your mono-valve?

I still need to diagnose the cruise - been working on higher priority items so far.

No, I have not fixed the always blowing hot issue. It didn't bother me in the winter, but now that it is warming up, it is getting on my nerves. I think it just moved up the priority list! Since my last post I have: replaced the climate control selector module with a known working used unit (thing you push buttons on in the dash), tested and replaced all of the vacuum pods (confirmed operation with mityvac), replaced inoperative vacuum solenoids, and replaced the coolant valve on the firewall. My HVAC system will blow very hot when set to "red", and will be ever so slightly less hot when set to max cold (without a/c engaged). When I rotate the temp wheel I can hear clicking and vacuum sounds, and the heat will then start coming out of the center vents. When I have the fan set to auto, it will decrease fan speed as it warms up (only tried this once or twice as I get impatient waiting on it to do something). I am defiantly open to some suggestions on this as well.

Any ideas on this? I test drove a car a while back that had the same issue. Sounded like it may be a common issue.

Hmmm,

The heat should not come out of the center vents. You verified that all your vacuum pods are in good order? They all hold vacuum?

I can't remember but center vent pod switching might be a function of the temperature regulator control box. It also controls the monovalve.

I wonder if your problem lies within that box.

Yeah, when I switch the temp wheel to cold air comes out of the center vents, and it is warm/hot with an outside air temp around freezing. I checked all of the HVAC vaccum lines and pods. I replaced the leaking pods. I will have to check the monovalve again - it was working last I checked.

sounds like the vents are switching as they should...

sounds like the monovalve is either being left open or stuck open. That could be either a problem with:
1) monovalve insert
2) monovalve solenoid/coil
3) temperature regulator control unit.

When I get it back on the road I will look more into the monovalve operation. Right now it has no front suspension under it... Thanks for the ideas.