More on my no heat issue (87 944S)

[turbokev]

Here's what I've checked..


-Fuse for Heat / AC checks out good

-Coolant is full and clean

-Blower fan works in all positions

-The little clips at the end of the threaded rods are fine

-I can move the air flow from defrost to dash and floor and all that

-Car warms up normally and settles between 1/4 and 1/2 on the temp gauge


On the S, the heater control valve is up front above the oil filter and I can see it clearly.
Vac line is hooked up.. but it doesn't really seem to do anything no matter where I put the temp controls in the car.
I can manually move the mechanism up or down..the vac doesn't seem to be interfering with me moving it.

I'm going to follow the vac line next and see where it goes and if the line is bad anywhere.

In cold start mode, which way should that mechanism be?
I'm assuming, with no vac to pull it up, it should be down all the way..
Is that 'heat' mode?? or does the vac need to pull that lever up to get heat?


Thanks for any help~

[VirginiaF1]

Yeah, I've found the same result on my heater control valve.. no movement no matter which selection.
But shouldn't activating the Defrost Button make the HCV open? Ya know, full heat and all that?
My HCV arm stays kaput even in defrost mode.. although I do get full heat on Defrost.
Kev, check your valve arm when Defrost button is activated.
Confusing..
Anyone...?

[ncspit80]

I just had the same problem. If the the hose on the dash air sensor is disconected or the the plastic piece inside the glove box is pulled out of the tube, the heater will not work.

[turbokev]

Originally Posted by ncspit80

I just had the same problem. If the the hose on the dash air sensor is disconected or the the plastic piece inside the glove box is pulled out of the tube, the heater will not work.

There is a hole in my glovebox that has a hose coming up to it..
Blows air in to the glovebox when the blower motor is on..
Here's a picture of the opening.. Does that look the way it is supposed to?




I'm assuming I need to take the glovebox out to check the tube that runs from the little
round vent on the dash back to the interior temp sensor?



Here's the heater control valve.. picture taken from the passenger side by the strut, looking
forward and down.. the blue is the oil filter (which will be changed to OEM asap)




The orange plastic arm is hooked up to the rod coming out the bottom of the little vacuum
canister that controls the valve.. it moves freely up and down manually, but does nothing
with the car running no matter where I set the heat controls, even if the defrost button is
on, it still does nothing..

When it is down like this, is there hot water going back to the heater core? or does it need to be up?

(I do have 'slight heat' in the car.. warmer than ambient temp.. but certainly not hot..

[ncspit80]

In my glove box there is a plastic piece that plugs into the hose. My heater control valve would not move until I reconnected the tube to the air temp sensor. I don't think you can do it without removing the glove box. Also helps to blow the dust out of the sensor.

[VirginiaF1]

Originally Posted by turbokev

When it is down like this, is there hot water going back to the heater core? or does it need to be up?

Hi Kev,
Just spent a good half-hour googling HCV operation:
It appears that "arm extended" (like your picture & My car's HCV currently are)
is the "No Vacuum/Default" position that allows heat into the cabin.. owing to Porsche's wise fear of customers freezing rather than sweating upon system failure.

So when you freely moved the orange valve arm to the closed position, did the Defrost Button still create hot air?

Your HCV looks as discolored by age and heat as mine; so we are both overdue for new ones, eh?

As far as the glove box hole,; yup, mine has one also.
Climate comfort for my spare DME relays and spark plugs.. LOL.

[turbokev]

when I manually put it up, it sowly went back down. So, I couldn't really tell in time
if there was any change.. I took the car for a 30 minute drive this morning and after
15 minutes or so I suddenly had heat.. normal hot heat..

When I got home I had a bunch of things to do so the car sat for several hours..

Tonight I took it out to get pizza (30 minute round trip) and this time got no heat again.


I verified that the flappers are working by watching the threaded rod down by the
gas pedal when turning the defrost button on and off I can see it respond by going up
and down right away..


So.. logic (and your default find) is telling me that the heater control valve is in the
right position to send hot water to the heater core..and the flappers / fan is working.

This leaves a couple options.. dirty / disconnected interior temp sensor..
Or air bubble in the cooling system that is residing in the heater core..

I did run the engine at 4000 - 5000 rpms in second and third gear while on my drive tonight
with no change to the heat situation and I've read that usually pushes the air though
at least temorarily and you get heat.. That said I'm going to bleed the system tomorrow
to see of I can get any evidense of air.. and I'll pull the glove box, check the air tube to the
sensor, and clean the sensor either way as well..

Hopefully I'll have heat (reliable heat) by tomorrow night~

[turbokev]

Latest update:

No air in the cooling system.. bled it running cold and hot.. no air.

Tube from dash vent to interior temp sensor is in place.


Here's what I did find though.. When I pulled the glove box there was a wire
harness pinched between the glove box and the bracket.. 4 wires, don't see
a place to plug it in..

There is another small 2 wire connector up next to the temp sensor air tube that isn't connected..

and finally, I found a 3 wire harness with just cut wires at the end stuffed behind the carpet.
I don't think its a factory harness.. Pictures of all three things below..

Any idea what the harnesses plug in to, and if they are related to the heat at all?
I'm running out of options to try..

[turbokev]

OK, Let me take a step back and start fresh with latest info and symptoms...
(as I have luke warm air, not hot heat and I've determined I do have hot liquid flowing through the core)




First off, what's been done / checked:

-Coolant is full, clean, and has been bled..there was no air in the system
-Heat control valve is in open position sending hot liquid to the heater core
-Blower motor fan works in all positions
-Sliders on the control module move air to floor, vents, defrost etc
-Tube that goes from the little round vent on the dash to the interior temp sensor is in place
-All fuses related to the heat / AC / climate control tested and are good

Probably not related, but the AC button lights up when engaged, but I don't think the compressor is turning on, and the engine cooling fans don't turn on.

The cooling fans do turn on after the car is shut off for a minute, that's normal.



In the picture below.. (taken from drivers floor looking up behind center console)

#1 moves when defrost button is pushed. Blower fan goes to high. Shut the defrost off and it returns back to original position.
#2 moves as I adjust the temperature knob..seems to have full travel.




In this next picture.. (taken through the glove box opening with the glove box removed)

#1 These pipes are piping hot when car is warmed up..super hot. Definitely sending hot liquid through the core.
#2 This blows cool air all the time in to the glove box..
#3 This is blowing 'warm' air.. not ambient temp.. but it does not blow 'hot' air.






So, Core has hot liquid flowing through it, temp control knob moves the flapper, but car only blows 'kinda sorta luke warm' air out the vents.

Is there another blend door I'm not seeing? Maybe thats controlled by the interior temp sensor?

I don't hear a little fan running for the interior temp sensor..

Any write up on removing and cleaning the interior temp sensor?

Anything else you can think of I should be checking?


Thank you!

[944 Ecology]

Since you know that you have hot coolant in the heater core, try removing the metal rod from the mixing flap, and moving the flap manually to see if the air becomes hot air, not lukewarm.

It might be that there is something restricting the movement of the flap. (Hint: that big metal bracket that holds a relay, obviously not factory)...

[fiat22turbo]

The vacuum canister on my heater control valve failed. The valve itself worked fine, but would never move due to the failed failed diaphragm. Double check that applying vacuum to the nipple will actually move the control valve.

Also, I think on some cars, there are two heater control valves for some reason.

A little coolant will always flow through the core, so that may be where you're getting a false positive.

Just a thought. Good luck!

[turbokev]

Originally Posted by 944 Ecology

Since you know that you have hot coolant in the heater core, try removing the metal rod from the mixing flap, and moving the flap manually to see if the air becomes hot air, not lukewarm.

It might be that there is something restricting the movement of the flap. (Hint: that big metal bracket that holds a relay, obviously not factory)...

Good idea.. That nasty bracket holds some sort of 80's kill switch, but it's inches away from the adjusting rod.

I'll try manually moving the flap to see what happens..

[turbokev]

FIXED!!


As soon as I unclipped that rod and moved it down a bit I could feel heat pouring out the vents..

Whoever replaced the clips on this car had secured the rod too high so the blend door wasn't opening far enough.

I moved the rod down about 3/4 inch and reconnected it.. Heat works now~


THANK YOU for the good idea.. I've been chasing this for a week..





.

[tamathumper]

If it weren't for previous owners, I'd have only done half the work I've done on my cars.

[944 Ecology]

Originally Posted by turbokev

FIXED!!

.

Glad you found it. The AC/Heating system on the series 2 cars is a black box, but sometimes logic and perseverance pays off.

[VirginiaF1]

Originally Posted by turbokev

FIXED!!


As soon as I unclipped that rod and moved it down a bit I could feel heat pouring out the vents..

Well for only having 53 posts over 12 years, you do make em count man!
Nice!
Can't wait to try that solution..
And you are the King of helpful pics with good labels.