Mondial heater issues

WOW, What a coincidence, I just developed the exact same problem with my car the other day regarding the defroster. I am curious to hear a response.

 

I'm no expert so take this for what it's worth: Here is a link that may be useful:
http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=2625
The buttons on the console (part 33) do control vacuum, and some of the actuators are visible on the drawing, parts 57 and 59. I suspect part 57 is the actuator that controls the door for the defrost. See also this page showing some of the ducting: http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=2617

It might be worth trying to get at the tubes under the console where they connect to the push-buttons and trying to create a vacuum to see if the door opens or closes. Defrost should turn on the A/C I think, but I don't know where the message gets sent to the compressor.

My suspicion regarding intermittent heat is a failing heater control valve. It has a thin rubber diaphragm and a fine screen, so they turn to goo and clog up after a certain amount of time. It's up in the passenger's footwell, in a really difficult location to access. It should make a quiet thumping sound when producing a medium amount of heat, and should go to full open (always hot) if the wires to it are disconnected. Perhaps something to test.

The valve is the same as BMWs of the same era, and rebuild kits are available for +/- $40. It's really easy to rebuild-take off two screws and replace the plunger. Too bad it's a massive pain to get out of the Mondial, what took me about 15 minutes with the BMW took about 10 hours on the Mondial. The valve is on the BMW firewall under the hood, at the high point of the system. For the Mondial: drain cooling system, remove passengers seat, remove carpeting and line with bags to catch any stray drip, jam head and hands into tiny space to get hoses and valve disconnected....yuck. But it sure is nice to have heat that works well.

Hope this helps.

 

Glad to help--but as I think about this more--the intermittent heat could also be an intermittent electrical problem to the valve: It could be grounding sometimes or not, or occasionally not being connected to the hot. I suppose you could rig up a connection to the two wires that had a light, so it would illuminate when energized. If it suddenly went solid on or off as opposed to pulsing you would know there was a problem. It seems Mondials benefit greatly from having all their wiring connections cleaned and jiggled--perhaps that's all it is.

When my heat quit I hooked a multimeter to the wires and watched the pulsations (+12,0,+12,0...) so I knew the system was working and it had to be the valve.

I sure wouldn't fix the valve without being pretty sure it was the problem. It may not sound bad to you, but you probably have better things to do.

 

Lightning, what year is your Mondial? I have an '81, which has manual A/C. My system did not work properly when I got the car, which tgurned out to be low vacuum due to many cracked and hardened vacuum hoses in the engine ccompartment. After replacing EVERY HOSE in the car, a monumental task, the HVAC worked fine, UNTIL the defroster motor packed it in. The motors that operate the doors are all vacuum operated. A new actuator (very cheap) solved the problem.

 

yikes.. may need to do this test... arghh.

 

Fwiw, my problem turned out to be a leaking vacuum line. Pretty simple fix

 

Darn, I knew it. My car has a bundle of wiring about the size of my wrist right up against the valve that really complicates removal. Interesting how clean it looks without the wiring. -which goes to the amplifier under the passenger's seat. My recommendation on draining the cooolant has to do with my zero tolerance for spilling coolant in the car, it is certainly optional.

Those are vacuum wine stoppers, aren't they? I'm not sure about getting drinks with you now...

 

Could you give us more details on the rebuild kit? Is it a BMW part? Part No? Or? Where can I get one?
Thanks much.

 

Could you give us more details on the rebuild kit? Is it a BMW part? Part No? Or? Where can I get one?
Thanks much.

 

It's a Bosch part, but common to both cars. Here it is from an online supplier:
ttp://www.autohausaz.com/search/product.aspx?sid=qcu452axw1yssr45txx1g455&makeid=800003@BMW&modelid=1012352@535I&year=1987&cid=24@AC %26 Heat - Climate Control&gid=6860@AC %26 Heater Control Valve

Or if you're in a hurry you could go to your local dealer and ask for the heater control valve for an '87 535i...

 

Thank you Martin and Peter. I have ordered the kit and when I added a fuel filter for my pickup truck I got free shipping. It is interesting that the cars all appear to be a bit different in construction in that area. Mine does not have a wiring loom in front of it as someone else mentioned, it appears my A/C lines go right in front of it and that will make it tough but I will take my time and get this done. The pictures are great, the unit is located in the same place on my 1987 US model.

 

bump

 

Bumping this thread again, I've read the 8 has a different valve and I also don't see that valve housing on my car. Does anyone have a photo of what the housing looks like on the 8 and what p/n the valve is on the 8? Thanks

 

The 8 has a very different heater I think you will need part 60929600. unlike the later models it is under the Dash so it's quite some extensive work.

For later models this solution is interesting to look at too if you have a heating issue. It's not always the solenoid.

peachparts . com/shopforum/diesel-discussion/381589-mtc-monovalve-no-heat-issue-solution . html