GRUWEZ

Guys,
Recently my 993 Targa has started to show some erratic heater behavior. Here are the symptoms.

1. Recirc off, defog off. Hardly any flow coming out of dash vents, even with the blower in highest setting. Windows fog up in damp weather conditions.
2. Recirc on, defog off. Normal air flow coming out of dash vents, in synch with blower speed ****. Windows fog up in damp weather conditions.
3. Recirc off, defog on. Heater fan cycles from low speed to high speed erratically.

Basically, when I drive the car in damp weather, I need to have the defog on all the time to prevent the windows from fogging up. Something is definitely wrong. Before setting out on a wild goose chase, perhaps the experts can chime in and let me know what to look for?

Thanks!
Rik

Mike J

Lots of times, excessive fogging on the windows means there may be water in the car. Lets check that first. Take a look under the floor mats behind the seats, and on the mats in the front. Do not just look under the carpets, try to feel the foam underlays - any leaks can get to the floors and that moisture comes out and fogs up the car. (don't ask how I know, I know).

Dig deep to confirm no problems. Stick your fingers in and under the carpets, under the mats.

It also sounds like you may have issues with your environment control unit, fans or some of the control valves. If you have access to a PST2, you can check that pretty quickly.

Have you checked fuses for the fans, etc? Can you hear the fan in the engine compartment start when you turn on the defrost?

Cheers,

Mike

GRUWEZ

Thanks for the tips, Mike. I'll do some investigation.
Regards,
Rik

GRUWEZ

Checked under the front and rear carpets. Bone dry.
All fuses are OK.
Any other ideas?

Thanks
Rik

Stealth 993

You may have a vacuum leak, that is causing the flaps not to work. You can take the trunk carpet out, & the plastic cover, then turn on the ac, & play around with the sliders. Then watch to see if the flaps open & close.

If you have a vacuum pump, you can put it on the flap where the vacuum line goes & test it that way.

GRUWEZ

Thanks, I will do that!
Regards,
Rik

william_b_noble

on my 993, I've noticed that the defrost actuators act oddly and will not always go into the defrost position - I attribute this to sticky plastic seals - interestingly enough, if I turn the ignition off momentarily (with defrost still selected) and back on, then the flaps actuate and I get defrost action. You may have the same or similar situation.

ToreB

GRUWEZ, you may have a couple of problems in your car.
First of all, I'd leave the thought of water leaks for now. I don't think this is your problem. If you have low air flow over the windscreen in damp weather it will fog up anyway.

I expect you have a fairly high setting on the temperature **** when you tried the scenarios you describe.
There's a fan in the engine bay that's supposed to start when you need hot air to the cabin. If this does not work you get fairly low air pressure, and the Climate Control Unit shut down the front fans as a failsafe mechanism.
To test the aux/rear fan, set recirc off, temp on minimum and fans to max. Slowly turn temperature **** up. The rear fan should start at low speed first, and then to high speed when the temp **** is way up or near max.

You may have a problem with one or two mixing flaps too. These regulate the amount of hot air from the engine. They are placed in each footwell behind the carpet wall. To test them, turn the temp **** to min and max and watch then flaps close and open. You may have to disconnect the air hoses to spot the movement.
Shot servos are fairly common. If they are stationary you most probably have to change them, and you may have a problem in the circuit inside your CCU that controls them both.

Since you get very little air flow you also may have a problem with your fresh air intake servo too. To test, turn temp **** to minimum and resirc off. Full fan. You should get full air flow as all air is taken from the fresh air intake. If not, press resirc button. If you then get full air flow, you have a working resirc flap and a shot fresh air servo. Very common, this is the most active servo in our cars.

You could check the state and operation of all flap servos by using an OBD tool. My DIY web site explain the details on the aux fan amongst others:
www.ccu.tore.bergvill.com
Cheers,
Tore

GRUWEZ

Hi Tore,
Thanks very much for the detailed diagnostic procedures. I will run the tests and check out what may be wrong.

Regards,
Rik

GRUWEZ

Hi Tore,
I ran the tests. The symptoms I notice are what you describe above.
Fan on max. No recirc: little air flow
Fan on max. Recirc: full air flow

Before ordering a new fresh air servo, how can I be sure it is the servo that is shot and not the CCU?

Regards,
Rik

ToreB

Good. Either use an OBD tool to read out any fault codes, or you can spot the movement (or no movement) by watching the servo while doing the test described above. Details on my web site.
Cheers,
Tore