jenskleis

Hi Everybody,

I just got in the door after returning from Le Mans. The best part of the weekend was... the drive there and back! My C4 is the best travel companion anyone can dream of.

But... things got a bit hot during the drive. When I open the sunrooof, or a window, my feet are immediately showered in a strong breeze of very hot air. It goes on, even with the aircon at full force directed towards the footwell. As soon as I close the sunroof/window the problem disappears. I also noticed that the ignition key lock gets VERY hot. Any ideas what causes this?

PS. I will post some Le Mans photos ASAP

springer3

I have not had your problem, but since the heat sources are in the back, the only way to get a lot of heat forward is through the heating system. You evidently have a control flap leaking.

The hot ignition switch is cause for alarm. You have a high-resistance connection either at an internal contact, or at one of the connectors. I don't know what you consider VERY hot, but if you can't keep your hand on it without feeling pain, it is too hot. Failing connectors eventually reach a stage called thermal runaway, where higher temperature causes higher resistance, which causes still higher temperature until something melts or goes aflame. Try feeling each connector while the system is still warming up. If you find one getting hot sooner than the others, you have found the problem. Cleaning and tightening the connector will normally fix the problem. If the problem is an internal contact, you need a new ignitions switch.

In any case, I would not drive around with anything electrical overheating. A cabin fire is too big a risk.

Adrian

Dear Jens,
What were you driving slow, we got back yesterday and had further to travel.
The problem with your heating is a pressure differential design issue.
What speeds were you driving at?
Did you have the temp control button selected to the blue dot position?
Close the footwell vent slider control (min position).
Try a speed test. Find out at what speed when you open a window or the sunroof that the heating to the footwell tends to open up.
The ignition switch gets warm anyway and I bet it is being heated by the hot air.
Ciao,
Adrian
964C4

springer3

How hot does the switch get when the heater is not blowing? Anything close to pain threshold would cause me to shut down and investigate.

Adrian

The ignition switch gets very warm (quite hot) over a period of time. However if it gets to too hot to touch and is of skin burning temperature then you will have smoke coming out of the dash because the insulation on the wiring will start to melt as will the plastic on the end of the key. Then you have a problem.
The ignition switch supplies power to the distribution system. The contacts in the switch are very meaty. Relays are the same. The ones that operate energised all the time get very warm to hot. The ignition switch has power (current) flowing through it all the time.
I have only ever seen smoke once and that was on a 924 and it was caused by the fuel pump relay but that is as they say another story.
Ciao,
Adrian
964C4

PS: Do a 10 hour drive and check the temperature of the rear seats and the floor in the rear. Quite hot. Very normal. The heating system also runs behind the dash and heats things up very nicely as well. There are also a bunch of control unit grouped around the steering column again adding to the heat output.

jenskleis

Many thanks for the good advise.

Adrian, just for the record, I left Le Mans rather late because my mother went for a spin in the 964. It was the first time I have had to fight a 60+ year-old family member for my car! Hence the late arrival in Lausanne.

I discovered the heat coming from beneath the dashboard (over the lower part of my legs) when driving around 100 km/h. This morning I tried at 50 km/h and the hot air comes out at soon as I open the sunroof or window. It seems that the flow of hot air increases according to how fast I drive. In all situations, I have had the air con on, the temp selector on the blue dot and the footwell slider on minimum. I also tried to direct the cold air from the air con to the footwell by closing the dash vents. It didn't help.

Thanks for the advise about the ignition switch. It got so hot I couldn't touch it... and burned something prescious when I put the key in my pocket... I'll check out the connectors asap.

Adrian

Dear Jens,
I advise you to check that your rear blower fan is not running when you are in the blue dot position. It seems to me that you are sucking hot air through the entire system in a big way. This suggests that the heater differential pressure valves are open or being opened.
I would also advise that you open the luggage compartment, take off the very rear black plastic cover and make sure that the mixing chamber valvces are in the full cold position. You can pop off the arms and make sure they are in the full cold position.
The ignition switch is being heated by the super hot air blasting into the footwell. You have to cut off this source of hot air first and then find out why it is getting through.
The hot air is generated in the heat exchangers. It needs a flow of cool air to generate the hot air. With the temp control **** in the blue dot position there should be no path for major hot air flow to get to the front of the 964.
Start with the rear heater blower. This should be off with engine at normal operating temperature and the control **** is the blue dot position.
The only other cause I can think of is the heater connection to the left blower has come adrift and when you open the window or sunroof this is supplying sufficient sucking force to draw the engine fan air through into your feet via the heat exchangers and believe me this will be HOT HOT HOT.
Ciao,
Adrian
964C4

jenskleis

Hi Adrian,

Thanks for the ideas. I'll do a bit of troubleshooting using your advise. I had a new alarm installed last week, so maybe they damaged or disconnected the heater connection. I'll also check the mixing chamber valves.

I will keep you posted on what is wrong.

Take care

Rocket Rob

I have one more idea that hasn't been mentioned. I had the same situation in my passenger-side footwell. The problem turned out to be that the heater hose in the footwell had been damaged and was leaking the heat into the car before the heater control valves.

I suggest laying in the footwell and look towards the wheel well, you will see a paper/foil hose going from the rocker panel up into the front trunk area. This hose was the one that was leaking for me. Fortunately, it was an inexpensive fix. I don't remember the exact cost of the part but it was less than $50, which for a 964 is cheap.

Hope this helps and good luck.

Jim Howley

I too had a problem with the front passenger side (car is LHD) footwell hose leaking.

My local car parts store had some foil flexi hose which I was able to cut to the correct length and it cost me about £5 in total.

jenskleis

Problem solved!!

I checked the pipe in the footwell and, indeed, there was a large hole in it. A closer look revealed that the pipe had also popped off at the lower fixing point. I assume the guy who installed my new alarm last week is to blame.

Anyway, I fixed it and a brisk drive with the sunroof open didn't cause any hot feet.

Many thanks for all the good suggestions.

springer3

Did that fix the ignition switch as well?

jenskleis

Yes, the ignition switch does not heat up any longer. Did a 2 hour fast drive from the Alps to Geneva yesterday (sunroof open all way) and the switch was nice and cool upon arrival.

shadopadla

Thanks for posting this! I have been having the same problem in my car. Nice superheated passengers ;-) Ordered the flexi hose part from Porsche dealer, total cost: 20 bucks. 17 something for actual piece, and 2 something for two hose clamps to keep the bugger in place when I get the part. Cheapest fix yet I think, if only they were all like this... speaking of, does anyone have any ideas on why the defroster only blows cold air? Car was switched to r134, but that was mostly in the engine bay correct??