conate

Just completed my trip from CT to SC. Was an awesome trip with no issues except one large one. The heat at our feet was very uncomfortable. The PO of the car mechanically shut the floor vents. Is there any way to subdue the heat from getting in. Running AC helps a bit but still very warm.

MainePorsche

How was this done ?

Could be a clue to its fix.

conate

I was told the vents were zip tied shut due to the fact that the seal would erode and fail. I heat typical?

MainePorsche

So, you have cool/AC ventilation up top and through the doors, but you 'feel' heat down under. If vents are tied shut you should feel nothing coming through them - if they were released it should be the same temperature air as up top.

Where EXACTLY are you feeling the hot air ingress ? May take a little investigation to ascertain. Often, some have felt a little heat ingress under the shifter area. There is an insulation under this area that may have shifted or be absent. I never heard of it making ones feet hot though.
If you were to cut the ties that bind, you may then get cool air on hot feet - not a complete fix to the problem.
A little sleuthing is in order.

Adamant1971

Yes, but more often the diaphragms fail causing a flap to not function. Also the heater control valve fails causing constant heat through the vents.

I would remove the zip ties the. Test the vacuum lines for each flap to determine what needs replacing and check your heater control valve.

You can access the vacuum lines that control the flaps by removing the centre console lower carpet side panel. You can then splice into the coloured vacuum lines and attach a mighty vac to test the diagrams.

Check out Dwayne's site.

http://dwaynesgarage.norcal928.org/1...0Procedure.htm

conate

I was told the vacuum lines were left on and just the linkage was zipped closed.

69gaugeman

Cut the ties. Somebody who has no idea what they were doing was in there.

If cool air comes out of the vents on top and door, then cool air comes out of the floor too. The system has the heater core and AC evaporator sandwiched and a flap operated by the heat servo motor moves that flap to uncover one and cover the other. The conditioned air then travels through the various flaps to the vents.

conate

I believe he shut the isolation flap from heater to AC. Car was in Las Vegas and he said there was no need for AC.

MainePorsche

This all needs to be confirmed somehow.
Makes sense if a Vegas guy disabled heater valve for he had no need for HEAT.
Why he would tie off the lower vents is non sensical.
If heater valve were disabled you would have NO heat coming through.
You can't have cool from above and heat from below through the duct system.
Inspect heater valve, cut those ties, and have someone drive while you get your hand on exactly where the heat is coming. Do this for starters. Report back.

FredR

Are your carpets/mats fitted?
If these are missing/removed then quite a bit of heat does come through the floor on a warm day from the exhaust.

When the flap actuators fails some folks wire the specific flaps to a fixed position that suits their needs best. if like me you do not need the heater, then it can be taken out of the loop altogether. My fresh air flap actuator has failed so for the time being I have locked the flap such that there is no fresh air make up & crack the windows open regularly. Not good to be anti social in such circumstances.

This is an unbeleivably dumb antiquated system for a supposedly high tech car of the late 80's. It was designed in the early 70's and they simply did not update it.

69gaugeman

Have to agree with you there. The climate control on my 93 Audi 90 was light years ahead of the 928.

Gonzotiki_666

And make sure you cat doesn't look like this!

conate

I now have heat blowing through all the vents if the AC is off. The only way to minimize it is to move selector slide to OFF position and manually close door vents. I am still not sure what position acts as fresh air position. Initially I thought it was only heating through the foot vents but found it is coming through all vents selected. If I turn on the AC it seems to override the heat. I have not been able to start troubleshooting yet but would like some input on what a good starting point would be.

Adamant1971

Sounds like a bad heater control valve, zip tie it closed or replace it. If it's not closing hot coolant is sent through the heater cor and you get hot air.

conate

Where is the heater control valve located?