elementsix

Belive me I have searched every threadon every notice board for 3 days and still can't find the answer. Read John 964 site and while very informative, only explains failed servos, which doesn't seem to fix my problem! The blower motor in the engine compartment is working - it does spin. There is major heat at the rear of the car leading me to suspect that flaps are not opening on the heat exchangers. The pipe to the blower motor is cold and the sensor (temperature I presume) on the top of that pipe was unplugged - could this be the problem? Replugging it made no difference (faulty?). I felt the pipes in the rear wheel-wells and they too are cold, leading me to believe that the hot air is not travelling up though the car. I suspect that the heat is going no further than the engine compartment.

Does the oil cooler play any role in the equation? Just a thought!

Any help greatly appreciated. Wife is giving me stick for buying a car with no heating/spending so much time in the garage!!!

Shane

hoffman912

this is a help thread as far as rennlist goes.. ie if you need help with membership, if there is a glitch on the website etc.

may i suggest you go to the 964 forum with this? i suspect you will get 100 fold more help there than on this section.

id give advice myself but dont know f it would pertaine as mine is much older than yours..

if it were a 912.. id say make sure your heater boxes are there and properly connected, not rusted out, and make sure that the cables are connected.

dont know if that would go in hand with a 964 though...

elementsix

One of those newbie mistakes!

dfinnegan

elementsix,

I'm not sure that I fully follow your description here, but I can tell you that the basic heat flow in the 964 is as follows:

Heat exchangers draw heat from the exhaust manifold.

The blower in the engine bay is auxiliary. It can be removed and is not present on RS models. A bypass pipe is used instead.

Beyond the blower the heat ducts split through a differential pressure valve. One path dumps excess hot air to the rear wheel wells. The other path goes to the climate control unit (CCU) mounted behind the dash in the rear of the front luggage compartment. The differential pressure valves are a simple mechanical system allowing the air to follow the path of least resistence.

At the CCU there are flapper valves controlled by the servos and fans to draw the hot air into the passenger compartment. When the CCU fans are active air is naturally dawn from the rear to the front. If the front flapper valves are closed there is no path for heat to reach the passenger compartment.

When the ccu flapper valves are (fully) closed and the rear blower is engaged all hot air dumps into the rear wheel wells. When the engine temp reaches a preset value (9 o'clock on the temp gauge, if I recall correctly) the rear blower engages and dumps excess heat to the wheel wells. You can easily determine this condition as the fenders get warm and the heat can be sensed blowing through the wheel wells.

A simple test could be to disconnect a servor from one of the flapper valves (servo 1 or 5), manually open the valve and then engage the passenger compartment blower once the engine is up to temperature. You should feel heat in the passenger compartment.

if you don't it could be that the duct work under the dash board has become disconnected. Check for heat under the dash.

The ducts under the dash apparently come disconnected and sometimes need replacing due to deterioration.

If there is no heat what so ever in the forward compartment then you'll need to follow the duct work back to the engine compartment to attempt to find a disconnect.

Hope this helps.

Good luck.

Dave

Indycam

Ohio elementsix
Do you have a digi camera ?
Can you post a photo of the engine from above and below ?
Lets have a look see at what parts are on your car .

"Wife is giving me stick for buying a car with no heating/spending so much time in the garage!!!"
What do you think she will say when its fixed ?

LeRoux Strydom

The red heater hoses connecting the heat exchangers covering the exhaust manifolds to the flapper valves could also be damaged or missing altogether. Get the car up on a lift or get yourself (safely) underneath the car and visually check the condition of the hoses.

Le Roux

elementsix

"Beyond the blower the heat ducts split through a differential pressure valve. One path dumps excess hot air to the rear wheel wells. The other path goes to the climate control unit (CCU)"

Thanks Dave - don't suppose you can describe what the differential pressure valve looks like? I'd say that my problem is there, as there is a lot of heat around the wheel-well. Also there is an electric sensor of some description inserted into the black plastic pipe leading to the blower - any idea what that is and what is measures/controls. This was plugged-out when I was rooting aound in the engine bay, so I reinserted it, but it made no difference.

I have already manually opned the flappers so I know this is not the problem - the heat is simply not getting up that far. The problem is further down the line.

I'll have a look behind the blower for the differenial pressure valve - wouldn't surprise me if that's unplugged too!

dfinnegan

The differential pressure valves are fairly small with no servicable parts. I doubt this is your problem. I've been down this road. i was convinced that I had problems with these valves and finally came around to realize they are simple "Y" connectors with a bit of intelligence.

I'd look as suggested above for the connections between the heater hoses to the heat exchangers and the duct work going forward.

Cheers,
Dave

LeRoux Strydom

Dumb question perhaps, but sometimes it is worth going back to basics. You are turning the temp **** on the CCU away from the blue dot, are you?

Le Roux

elementsix

Most definitely Le Roux! Servo arm on the drivers side (LHD), Servo 4 as you are looking at the car, is stuck in the open position (9 O' Clock), which indicates the flap is open, but again, no hot air! I'm stumped by this - I still think the problem is further down the line!

jimq

Maybe some critter built a nest in the hot air tube or box before it gets up front. May have cooked rat somewhere in the system!

elementsix

I doubt it! The heat is duping out the rear-wheel wells instead of travelling up along the car - even with the front flaps controlled by the servo manually opened! The problem lies at the heater boxes at the rear - a differential pressure valve? Is this valve plugged-in? At the side of the blower motor I can see a disconnected round plug with 3 male and 3 female parts - could this be the connector to the valve?

dfinnegan

elementsix,

The diff press valve you are after sticks right into the rear wheel well. There is a vent maybe an inch or two wide by a half inch high. This is the wheel well dump side of the valve. The other side is a couple of inch diameter connection to the hose/duct work running forward.

If you like I can send some diagrams of the whole system, but they are too large to post. Send me a private message (PM) by clicking on my name to the left in this message and include your email address and I'll forward along the pics.

Could be that this is where the connection is broken. You'll also get a chance to take a look at the differential pressure valve.

Cheers,
Dave