Another 140 with no heat
 

Guys,

I have a 93 500SEL that has a problem with the heat. I get a slight blowing of air (with fan on MAX) from the front vents, both center and sides. However, with the temp selectors both on HI I still get no heat. I've found that if I depress the red "booster" in the center, I can get some heat. It's not the kind you could cook a hotdog over, but it would do. In the rear, I get nothing but cold air no matter I do up front.

I found this old thread http://www.peachparts.com/shopforum/showthread.php?threadid=64175&perpage=15&highlight=heater&pagenumber=1 , but there is never really an answer. I've just flushed and filled the radiator with MB coolant, and replaced the tstat. I also tried the diags test JimF mentions on his site, but I too could only get the sensor values to come up. It's warm here now, so it's no big deal. You'll get a kick out of how I found out I had no heat. I was driving home one particularly hot afternoon when my engin temp guage started to read around 105, so I thought I'd turn the heat on to vent it a bit. Ha! Foiled again!:(

I'd rather not dump yet another $500.00 into this thing right now, if you know what I mean. If I show up at the inde shop again they are going to give me my own locker!

Thanks all!

UPDATE
 

Thought I'd offer an update.

While driving at highway speeds this AM to work, I tried the heat. No heat, no blowing of the fan either until I engaged the red "booster" button on the center console. then I got luke warm air from the front.

HELP! I'm starting to miss my Lexus! Someone reassure me!

update II - I have codes
 

OK, I finally got the DTC codes out of my AC system. Here is what I have:

Codes Meanings
E0 43 A/C system coolant temperature sensor (B10/8), open or short circuit **)
E0 74 Heater supply unit circulation pup (A31m1), open or short circuit *)
E0 75 Heater supply unit circulation pup (A31m1), open or short circuit **)
E0 83 Heater supply unit left duovalve (A31y1), open or short circuit **)
E0 87 Heater supply unit right duovalve (A31y2), open or short circuit **)
E0 99 Auxiliary fan, 1st activation, open or short circuit **)
E1 3 Auxiliary fan, 2nd stage activation, open or short circuit **)

Sounds like the heater supply unit (what ever that is) is bad. I wonder about the others though. Could I have installed the Cool Harness incorrectly? Any ideas?

You just need a heater supply pump. Very easy to replace. 4 screws. I have a used one if you are interested.

Oldsouth,

Sorry to be so late getting back to you. I was out of town. I read your post to sab about his heating problem, so I guess I understand how you ended up with a used pump on your hands. I think I want to go with a new one, but I'm curious about where you found your new one, and how much it cost? It sounds like a pretty easy job, so I think I can take care of this one on my own if I can find the part.

Right here on this site through Fastlane. If I were you, I would take the pump off and try oiling the shaft to see if it would work. If it is the shaft that needs oiling, you can oil it if it has not already burned the motor up.

Not to sound smart- but why were you wanting to use heat in the middle of summer? Just a thought.

The way the system is designed, when the set temperature point is reached, it uses heat to slightly warm the cooled air and cuts the fan speed. The evaporator temperature stays 37-43 degrees. This keeps the humidity level lower for the air coming out the vents.

heat in the summer?
 

Well, oddly enough, on a really hot day here my temp guage was up around 105 degrees, so I thought I'd turn on the heat to vent it a bit! That's when I noticed that I couldn't get any heat in the cabin.

I'm begining to think this car is cursed!:mad:

Olsouth, I'll try the oiling of the shaft and see if that helps. As far as I know, the previous owner had heat the last time he needed it, which was probably back in March. I"ll let you know how it turns out.

Thanks guys!

I see. Now it makes sense. Best of luck.

What is a heater supply pump and where is it? And what part do you oil to get it working again? What does it look like? I have the same heater problem in my 140 as well.

thanks in advance,

Airdam

A heater supply pump is part of the REST system that heats the car when the engine is off. It also supplies heated water to the heater core during normal operation. It is on the drivers side behind the plastic panel just in front of the fenderwell. It is the round part that sticks up and is held on with 4 screws. Open the coolant cap before removing to relieve pressure. It is a motor that drives an impeller on a shaft. Usually the shaft corrodes over time and burns the motor out. Sometimes if it is just squeaking, you can oil the shaft to fix it.

Fixed? We hope so!
 

OK. Because I hate it when there is no resolution to a thread, I thought I'd offer what appears to be the end to my heat problem. The indy shop had my car for 3 days, during which time they were torn between replacing the duovalve and HSCP, and replacing the Climate Control Unit. They ended up leaving in the original CCU, and doing the duovalve et al. I picked it up on Friday evening and I had heat. Saturday AM I checked it again and I had no heat. No heat again on Sunday. Took it back Monday afternoon and on the way I had heat again. Very strange. They replaced the climate control unit, and now I seem to have heat any time I want it. (Of course, it's only been 2 days so I've still got my fingers crossed.)

Total bill to get heat in August: $1,600.00. Could have ordered the parts here for about $900.00 and done it myself, but the car might still be in pieces. :eek:

I hope of this helps someone out there somehow.