No heat problem. need help solving.

[vsg914]

I got my FSM and have spent many hours since reading and researching. I'm having a no heat problem. The dash vents have not worked for the ac for a while. All air comes out the defrost or floor. When I first reinstalled the hvac head we had heat or ac on demand thru the temp selector. Now I just get cold air. The head gives a dtc of 02. Using the flow charts, it tells me to enter into parameter 34 with the Tech-1 at the programmer. That is where i'm stuck. Is this another diagnostic tool? I have disconnected the battery as per instructions on page 1C-6 to restore the logic. No change is noticed. Where to look next? Do I have a vacuum problem?

Thanks in advance,
Curt

 

[vsg914]

This forum rocks! I decided to check out the the tech articles at the top of the page and navigated to a tech bulliten that gave the entire sequence for reading the output at the control head (which I did not see in the fsm). Found parameter 34 and numbers were in spec. Followed the flow chatr to parameter 24 and both hot and cold readings of 128. FSM says this is the default/mid position to "allow full hot or full cold control". I still have no heat at full hot. Vent position gives outside temp air. Full defrost also gives outside temp air. Looks like next is to remove blower motor to see if something is blocking the door and freeplay. Have to wait till tomorrow for that.

 

[catbert]

There ya go!

 

[gmjunkie]

This forum rocks! I decided to check out the the tech articles at the top of the page and navigated to a tech bulliten that gave the entire sequence for reading the output at the control head (which I did not see in the fsm). Found parameter 34 and numbers were in spec. Followed the flow chatr to parameter 24 and both hot and cold readings of 128. FSM says this is the default/mid position to "allow full hot or full cold control". I still have no heat at full hot. Vent position gives outside temp air. Full defrost also gives outside temp air. Looks like next is to remove blower motor to see if something is blocking the door and freeplay. Have to wait till tomorrow for that.

Before you go to all that trouble be sure to check the vacuum check valve under the right fuel rail cover,There prone to going bad from age, leaking,causing vents and blend door malfunction!~!!

Check all the vacuum lines too for cracks or leaks while your at it!

 

[vsg914]

Thanks Junkie. I knew there was a vacuum valve somewhere. It was on my list too, but I'll put it at the top of the list.

 

[boomdriver]

The one that the Junk man is refering to is a check valve...small cylinder about 1/2" in diameter....3 nipples. 1 in and 2 out.
That is the "feed" or vac supply line to the cabin. You will then have 2 or 3 plastic hard lines inside the cabin with the wire harness (yellow, red plastic) that go to the control head manifold or "programmer" that controls the vac and where it works.

IIRC the "blend door" is electrical. Just a small motor/actuator that moves the door to access cold/hot as needed. There should be a test process for that in the FSM. Those are prone to failure. I think you can see the actuator and the lever if you can get upside down and twist your head around just right....its a challenge but you might be able to see it trying to operate (or not) if someone else will operate the controls while you look, to signal a different need for air blend.

 

[vsg914]

I looked at the valve, hoses, elbows, & tees. Nothing visible wrong. I found a link, I think at one of hib's articles, for checking that part of the vacuum system.Boom diver, under the dash? Is that the same door they refer to behind the blower motor?

 

[John Robinson]

Ok Junk time for the blow test of the valve. I would give it but I can not remember which fitting to blow into or is it suck on.

 

[gmjunkie]

Ok Junk time for the blow test of the valve. I would give it but I can not remember which fitting to blow into or is it suck on.

View attachment 6276

You should not be able to blow through the larger single end,but should be able to draw air through it!~!!

 

[vsg914]

Thanks guys. Angela has the car at work today. I'll check this stuff tomorrow and let ya know what I find. I hate it when I give someone advice on my Porsche forums and they never respond whether it helped or not.ad

 

[boomdriver]

Yep...
Pulling the BCM is probably the easiest way to peer inside and watch the fresh/recir door operate. You can pull the blower motor if you suspect a lot of trash has been inhaled thru the screens under the windshield edge....I looked in mine last year while swapping out a blower and found over a handful :ugh of leaves and debris stuck in the edges of the evap core, and some stuck in and around the door. That trash does not help the air flow and could potentially jam up a door. Depends on how much and what kind of trash. After seeing that I added another layer of screen to my factory screens to help keep trash from being pulled in with fresh air.
The yr models differ, and I'm not 100% on your air box but I think the return door inside is along the rt side kick panel near the firewall. Early yrs were straight vac operated while later yrs were electrical motor actuators that would run the door.
When you get the chance, look at the FSM componant drawing for the a/c hvac system and it will show all the actuators, which does what and how to test. The fun part is accessing some. If the flow is either def or floor thats default for a non-op door and usually indicitive of either interrupted vac or a faulty door actuator.

 

[vsg914]

Thanks BD. A little more useful info. On another note, The first check on one of the flow charts was whether the cruise control worked or not. How is the cruise connected to the climate control? do they share a vacuum source? I ask cause cruise doesn't work either.

 

[gmjunkie]

Thanks BD. A little more useful info. On another note, The first check on one of the flow charts was whether the cruise control worked or not. How is the cruise connected to the climate control? do they share a vacuum source? I ask cause cruise doesn't work either.

Yes they do!1 of the lines from the check valve go's in under the dash,the other gos to the cruse and on past to a ball like vacuum reservoir in front of the left front wheel behind the bumper! You need to check All of the lines and vacuum reservoir.If it's leaking somewhere you won't have enough vacuum reserve to work the doors or cruse!~!!

 

[vsg914]

Hmm, Before this all started the supplied air would go from hot to cold and back to hot again in just a few seconds, no matter where the temp was set. I did try to pull a vacuum with my mighty vac from the ports on the cruise control with no vac at either nipple. One had vaccum with the engine running.

 

[vsg914]

Ok, finally found where the check valve is susposed to be, but there is only a tee. One nipple goes to the manifold, and the other two go into a wiring harness. One of those lines pumps about 15lbs in 3 pumps and leaks down. The other will only build 3lbs with 15 pumps of the mightyvac and slowly leaks down. I pulled vacuum on a line that is attached to a tee under the cruise box and appears to go the resevoir. It also only acheived 3 lbs with many pumps and started leaking down. I'm gonna put it on the lift so I can access the bottom of the resevoir to check the vacuum there.

BTW, the plastic tee fell apart in my hands.

 

[gmjunkie]

Ok, finally found where the check valve is susposed to be, but there is only a tee. One nipple goes to the manifold, and the other two go into a wiring harness. One of those lines pumps about 15lbs in 3 pumps and leaks down. The other will only build 3lbs with 15 pumps of the mightyvac and slowly leaks down. I pulled vacuum on a line that is attached to a tee under the cruise box and appears to go the resevoir. It also only acheived 3 lbs with many pumps and started leaking down. I'm gonna put it on the lift so I can access the bottom of the resevoir to check the vacuum there.

BTW, the plastic tee fell apart in my hands.

No need for a lift,2 small bolts hold the reservoir
on the splash shield,Check it for leaks. If the reservoir holds vacuum,the plastic line is cracked somewhere in the harness.I usually run a new rubber hose,because it'll usually take for ever to find it!~!!

 

[vsg914]

Resevoir holds 15lbs with no leak down. I'm gonna check the hose from the resevoir to the tee at the cruise.

 

[vsg914]

I also removed the blower control module. The door looks like its fully shut against the pasenger side opening.

 

[vsg914]

line from can to tee leaks very slowly.

 

[vsg914]

Junkie, Run a new hose from where to where? Programer to vacuum source at mainfold?