When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Just purchased a 1989 Silver Anniversary Special Edition. Had been looking for a G-50 car for quite some time and this one spoke to me.
I have owned air cooled cars most of my life (beetles and busses), so while I understand the whole deal with heat exchangers and the various flaps and control surfaces that make them work, I am having trouble sorting out the controls on this car (very different than the "CCU" unit in my 993 (obviously).
During the 1,100 mile drive home from picking up this car, on the second day, the AC quit blowing cold _and_ heat began "wafting" from drivers' side dash vent. No movement of the between seat controls (which open the "flaps" in the heat exchangers), I had not touched them and confirmed them to be in the down position. All dash controls slid all the way left.
The heat was not coming out at a high pressure, nor in any great voluum, but on an 86 degree day, in the rain, with windows up, it got pretty uncomfortable.
I have the car on my lift and the heat exchanger "flaps" appear fully operational, cables not broken, not too rusty, and are fully closed with the between seat levers in the down (on the floor) position. Also, the owners manual has a great picture of the dash controls, but no explanation of what they do? Top 2 sliders are for fresh air I believe. Middle slider directs air (cold or warm) either to defrost or to floor. No idea what the bottom slider (red ****) does? Obviously heat related due to color.
"..in the rain..." More likely than otherwise your evaporator froze up.
Many owners (your PO?) "tweak" the thermostatic switch calibration(***) to get quicker initial cabin cooldown but then must remember to reduce the cooling level else the evaporator will freeze up, even more likely in a humid climate.
Some owners will even "muck" with the TXV factory calibration in order to get the generally underperforming factory A/C system to cool a tad better, but then that's another "tweak" that might lead to evaporator freeze up, again, especially so in humid climates.
Did some searching and found great info on heater controls. So I think I have that sorted.
Still curious as to heat into the car when all controls off. I guess it is an air cooled German sporty car thing...
With the evaporator frozen up the heat of the blower motor, coupled with very little system "wafting" airflow, may have felt as if heat was coming out of the vents.
Also, there is a fairly common failure (along with an also common, but misguided, DIY fix) involving the cabin heater blower control module. The factory design is such that the power for foolwell blower motors is disabled unless the cabin heater blower in the engine compartment is powered. The reed relay in the control module is a fairly common failure point and the DIY fix is to simply bypass the reed relay.
The upshot of the DIY is that now the footwell blower motors will run if the console speed control switch is in any position but off.
In you case, assuming the DIY fix is in place the footwell blowers might well have been running at minimum speed, drawing 86F air into the cabin from under the rear wheel well area.
WWEST, thanks for the info. I think Evap Freezup might be the thing. I have not driven the car since I got it home, so have not had a chance to see if the AC is still blowing warm. All blower motors seem to work, but I have not had much time to really explore the vehicle yet.
The evaporator does not actually freeze up. It gets condensation on the fins and "freezes over" if the temperature is set too low. Try turning the temp **** to mid-way and I think it will melt the ice away. You can then move the temp **** to what position works best for your car.
With the factory design intact the footwell blowers are disabled unless the cabin heat blower is powered, drawing enough current through the reed relay coil to close the reed relay contacts. The reed relay often fails and the picture shows the inadviseable DIY fix. With the modification the footwell blowers may run even with the red heat control levers in the off position.
Might well be the source of 87F heat and exhaust gasses "wafting" into th cabin via the window/windshield "defrost" ducts.
So, WWEST, I should look in engine compartment relay/electronics panel for this reed relay coil and see if it has been jumpered and/or if it has failed? The car is very unmolested so I doubt that it has been jumpered, but certainly worth checking out.
Any chance you have a pic of what I'd be looking for? I am very competent with most mechanical issues on these cars, but (and I hate to admit it), the electronics are still somewhat "magic" to me.
My ex-wife complained of heat coming into the passenger footwell and upon examination, I found that the flap was not completely closing at the heat exchanger even though the lever was all the way over. WD-40 and some sandpaper cleaned out some rust and other gunk that had built up on the valve and now the flapper door closes completely. You will need to pull the hose off to verify.
Yep, flapper boxes love to stay open just a crack. They can be removed, disassembled, inspected, and readjusted. My first attempt to fix the problem was to adjust the wire and clip on larger springs. The last solution was to replace them.
Thanks for the thoughts on the heat exchangers/flaps. I have had the car up on my lift and inspected the heat exchangers/flaps. Flaps appear fully closed when control levers in the cabin are down (on the floor), and seem to work properly overall. I did give them a coating of WD40 while I was under there.
So, WWEST, I should look in engine compartment relay/electronics panel for this reed relay coil and see if it has been jumpered and/or if it has failed? The car is very unmolested so I doubt that it has been jumpered, but certainly worth checking out.
Any chance you have a pic of what I'd be looking for? I am very competent with most mechanical issues on these cars, but (and I hate to admit it), the electronics are still somewhat "magic" to me.
If the footwell blowers will run with both heat control levers fully down then your control module has the DIY mod...
On further thought...make sure the cabin heater blower does NOT run with the levers fully down, remote chance that microswitch has failed.
Talos Takes Your 991 Porsche 911 GT3 to the Next Level for a Cool $1.13 Million
Slideshow: Talos Vehicles has transformed the Porsche 911 GT3 RS into a carbon-bodied, race-inspired machine that costs well over $1 million before the donor car is even included.
9 Vehicles Porsche Helped Engineer that Aren't Porsches
Slideshow: Long before engineering consulting became trendy, Porsche was quietly helping other automakers build everything from supercars to economy hatchbacks.
9 Features and Characteristics That Only Porsche People Understand
Slideshow: Some brands build cars. Porsche builds traditions, obsessions, and a few habits that stopped making sense decades ago but somehow became part of the charm.
This Builder Is Turning Heads With Its Slantnose 911 Creation
Slideshow: A small Polish tuner has reimagined the Porsche 911 Slantnose for the modern era, blending 1980s nostalgia with widebody tuning culture and serious performance upgrades.
Porsche 911 GT3 Artisan Edition Pays Homage to Japanese Culture
Slideshow: Porsche has created a Japan-only 911 GT3 Artisan Edition that blends track-ready hardware with design cues inspired by traditional Japanese craftsmanship.
Porsche Reveals Coupe Variant of the Electric Cayenne With a Fresh Look
Slideshow: Porsche's latest electric Cayenne Coupe blends dramatic styling with supercar acceleration, turning the brand's midsize SUV into a 1,139-horsepower flagship.
Heat & AC control Q
