plain fan

Time for an update.
1) My heat problem is definitely not related to the flapper boxes beneath the interior rear quarter panels. I got one from Cory at Planet9Eleven and replaced it at his shop. Unfortunately in the 50 miles that I've since driven I have already partially melted the piece!
2) I decided that the differential pressure flapper valve was bad. I spent several hours today beneath the car trying in vain to get the passenger side out. You might have noticed I said in vain. There is one bolt that I couldn't get to and therefore couldn't get the piece out.
3) I pulled the hose running from the heat exchanger to the valve and managed to determine that the flapper inside is indeed working.
4) I moved to the servo motors up front and guess what; #2 (looking into the trunk) does not move when changing from blue dot to red dot or vice versa. I know that #4 controls the driver side and it does move correctly (compressed = fully closed/full cold air).
5) Do both servo motors #2 and #4 work the same way? In other words is closed compressed for both sides? #2 is fully compressed but I get heat radiating on the passenger side area. I plan to pull the servo motor and perform surgery but I wanted every ones input.

Jeff do you still have the second pair of plastic interior flapper parts?
Jason can you still post the second picture that you mentioned?

Thanks,

Jeff Curtis

#2 and #4 do work together, although they operate in opposite directions, if I remember correctly...one goes clockwise to shut of the heat, the other counter-clockwise...if #2 is NOT operating, that is the culprit...I had to change that one out about 2 years ago, due to the same problem you're having. I was under the impression the heat was radiating from the rear of the compartment, passenger side - sorry, or I would've suggested that. I just changed out #4 because the same problem appeared on the driver's side a few months ago...along with a "quirky" CCU.

Yes, I believe I still have the plastic doo-hickeys, I accidentally bought TWO sets of them about two years ago, I'd have to locate them in a box somewhere, not too hard to find though.

JasonAndreas

There is a small opening .5" x 3" that the seatbelts fit through.

The first few years I had the car I stored it in a "tent" style garage out in my backyard and the mice got in during one winter. I ended up wrapping the base of the car with a roll of copper sheet that was 1 1/2' wide and never saw them again (my new cat also helped out a little).

plain fan

Thank you Jeff and Jason.

I've got an update. I pulled #2, inspected, cleaned and reinstalled. #2 now works corrrectly but that wasn't my problem. It had stopped working in the full cold/no heat (closed mixing flap) position. I operated the rod and it is working correctly.

So now I'm back at the differential pressure flapper valve. Is it internally spring loaded? Has anyone removed one; if so how did you do it?
Thanks again,
Grady

eyeslasher1

i'm having a similar problem on 993 section

JasonAndreas

No, it just rotates freely on a hinge. Occasionally when I shut my doors I can here the flapper valve move (it makes a click) but I can't think of another way to test them.

I removed mine to clean/polish when I had my transmission sitting on the floor next to the car. There are two M6 locking nuts holding the flapper to the car body. You shouldn't have any trouble with the lower nut but the upper nut is going to be difficult to reach, almost but not quite impossible. You might be able to undo the left (driver in USA) side flapper with an extension and a socket but on the right side the starter is in the way. You could try a swivel socket extension but you'll probably suffer less agravation with a ratcheting wrench. Sears has an inexpensive set that will ratchet back in 5 degree increments but I don't know if it will fit. Where exactly is hot air entering the cabin?

plain fan

Jason, I was able to get the lower nut off but you're right about the top nut. I tried for several hours using different tools trying to get the upper nut off. I could only get it to turn a bit but then the nut was out of position for me to get a socket or a wrench on it to make another turn.
I took off the hose from the heat exchanger and was able to move the flapper inside easily. So now I'm really puzzled. I know that hot air is entering the heating tube running towards the front of the car but since the mixing chamber is closed none of it is coming out of the vents. It just sits and radiates heat in that area. I'm really open to all sorts of suggestions now for what to look for! The passenger side heats up enough to melt plastic parts and scald bare skin when it touches the metal in that area.

Bertrand

I had a similar problem, everything worked OK but the right side flexible heat hose (on the side of the footwell) was VERY hot all the time.
Turns out that the hard plastic elbow connecting the flexible hose to the mixing chamber through the metal plate of the car body was misadjusted with regard to the mixing chamber inlet (about 1cm downwards).
I reconnected it properly and now everything's fine.
(seems like the leak was big enough to prevent the differential flapper to close completely).

Cupcar#12

is it possible to disconnect the mixing chamber flapper and leave it closed entirely.
I am trying to turn off my heat

also does the flapper automatically close when the power is off (i.e. the fuse is pulled)
or does it stay where ever it was last set?

i do not have the rear interior flappers in place - putting them in would require cutting the carpet which i don't want to do right now.

Cupcar#12

Another question -
Can i just remove the mixing chambers w/o triggering a fault light - heat is not an issue right now for me (driving to San Diego - not having heat is Important to me )

this might just be the solution for me short term until i can either track it down or simplify and lighten the system.

One more question - are the mixing chambers on/off switched only? if so are they on (heat) with current applied (as i surmise) or off with current applied

MSchett2

This may be obvious, but have your considered the oil lines? You say, "This heat doesn't come up through any of the vents, it just seems to radiate from the passenger side door sill and rear quarter panel area." The oil tank is in the rear quarter panel area and the oil lines run along the passenger side door sill. It is not unusual for those area to get warm once the oil heats up. You have very hot oil running inches away.

MisterRisky

Rob, I've been chasing heater gremlins for weeks. On Sunday when I set the car to full cool (as off) and turned the fan up, I had a cooking thermometer down the dash vent... temperature of 125! Smokin! After making sure both servos worked great I unhooked the connecting rods from the servos and ensured that they were in the right position, not too deep, not too shallow. I was told by another Rennlister that his actually pushed too far, resulting in a leak. No dice for me. They were properly adjusted so I yanked my driver side mixing chamber open. Yeah, that's the hard one if you have AC 'cause of the pipe locations. I'll take pics and post them soon. So that's my qualifications for now answering your questions

Can you remove the mixing chambers w/o a fault light: Yup. I yanked the drivers side off and ran the car with it open. No fault light. But if your mixing flaps are leaking or open, you will just heat up your luggage compartment and then blow that hot air into the passenger compartment. Actually because of the heat of the oil cooler, you may find it warmer pulling air from the luggage compartment if the flappers were not leaking.

Are the mixing chambers digital (on/off only): Nope. They are servo controlled and the servos can be any position between wide open and closed. When you adjust the temp just a little it may open a servo just a bit. Because of the servo, the flappers stay where ever they are when the power is cut.

I hope this helps. I will keep fighting with my mixer flaps and keep the list posted on what I find.

-JD

dfinnegan

The flapper valves are simple pressure sensitive valves. The flapper floats entirely free within the Y-shaped valve. When the forward vents are closed the exit to the wheel wells presents a lower pressure and the flapper simple floats to allow air to exit into the wheel wells. As the vents/fans in the passenger compartment are opened and/or the fans are turned up, the pressure on that half of the Y-shaped exit presents a lower pressure and the hot air simple flows that way.

In essence, there is no valve at all! It is "logically" just a Y connection from the rear splitting to the front or the wheel well. When air is blocked to the front (front servos closed) then air exits to the wheel wells.

MisterRisky

Just to be really verbose and (hopefully) eliminate some confusion, what dfinnegan is talking about is the flappers in the rear wheel wells (correct me if I am messing up here). I interpreted Rob's question to be related to the mixing chamber valves which are in the luggage compartment behind the gas tank.

Rob, please ask away with more questions. Dfinnegan has been of great help to me in diagnosing my problems. I have not solved them all yet, but I have eliminated a number of things with his help.

-JD

Cupcar#12

Actually i was talking about the Flappers in the rear of hte car - forward of the engine. This is the diverter where heat first enters the system and can be diverted to the wheel wells - I was thinking about removing these. I do not want heat to get into the sill tubes at all.

I will probably try to install the flappers in the rear compartment and see if that fixes it - this is starting to make sense in a way to me - my heat issue first started when the roll cage was installed (since removed). and the Flappers were removed to allow for bar clearance.