Porsche 924 - Heater blowing hot!

Dades

Looking to any 924 heads out there for advice...

The heater in my '83 924 has stopped blowing cool air completely. It now blows hot air regardless of whether the knob is at the blue or the red end of the slider. The cabin is like an oven after 10 mins on the road!

This may have coincided with me messing about with relays. I swapped a working relay from 8, below (Additional high beams) into 6 to see if that got my rear defogger working. It did - but possibly at the expense of cool air.

I checked the fuses and they are all fine.


http://www.connact.com/~kgross/FAQ/944faq12.html

Is the relay @ #3 - "Blower" - something critical to cool air? Or where does the cool air come from - and how did I break it?

Thoughts welcome! I've a long trip planned on the 8th and I don't want to have to wear speedos in the car. :pac:

macplaxton

I know zero about 924 heater systems.

I know a bit of how to search for these things though.

So two questions:

1) Is the heat dictated by a water valve opening and closing to allow water through the heater matrix?

If so, then the cable has snapped, or more likely come away from the valve control arm where it is secured/clipped.

2) If the water valve is a vacuum controlled one, then if you loose vacuum it will stay open.

If this is the case, then the vacuum pipe needs to be reconnected or vacuum leak fixed to restore control.

Dades

Good questions... now I just need the answers!

macplaxton

Probably while messing with the relays, the control cable was disturbed at the valve end. Or just co-incidental.

Something sounds like it's just popped off anyway.

Kenny Logins

Good info here - http://www.porsche924-944.nl/manual/Haynes/02_Cooling.htm#_01_023

Dades

Hmmm. So now I've a better idea of what to Google, it's looking like the Heater Control Valve, or the cable attached to it. I know the cable is hooked up to the heater controls alright as I can see it shifting back and forth behind the console.

So maybe it's come loose from the HCV, or the HCV itself is knackered.

I did have a look in the engine bay while my 6 year-old turned the heat on and off from the cabin, and saw nothing moving, though I didn't really know what I was looking for.

Good stuff. Food for thought here now.

Dades

Okay, so I did some investigation under torchlight last night.

I found the heater control value in the engine bay. I can manually move the yellow (ish) plastic arm by reaching in, but when I move the heater control in the cabin nothing moves in the engine bay. Clearly there's a disconnect between the cable hooked up to the HCV and the heater controls.

This may be good news, as I might be able to find where the connection is broke and rig something up. Will probably mean pulling out the heater controls but hopefully that won't seem too difficult.

Kenny Logins

Looks like a snapped cable or it has broken free from the lever.

Dades

LIGHTNING wrote: »

Mine is doing the same thing! Cabin is roasting hot which is unusual as 924's aren't known for blowing really hot air! I am keeping a close eye on this thread

I suggest you start at that valve in the engine bay! It seems if that is stuck open you'll get hot air all the time.

The question is why is it stuck open - knacked valve - or failed connection to the heater controls? (In my case I think Kenny is right.)

Normally this time of year it would be nice to have heat on tap...

Kenny Logins

Cable-tie should see you through the week.

Kenny Logins

No. 25 is Part No. 477819341 but this may be an earlier model

macplaxton

Kenny Logins wrote: »

Looks like a snapped cable or it has broken free from the lever.

Yes, although I'm erring for the lever.

Dades wrote: »

The question is why is it stuck open

The valve itself could be stiff causing the cable/lever to break, or the cable could be stiff causing the cable/lever to break, or the cable/lever just broke without any additional stress.

Dades wrote: »

Normally this time of year it would be nice to have heat on tap...

In the "good old days" it was on tap. At this time of year you lifted the bonnet and turned the tap on at the back of the head.:D

LIGHTNING wrote: »

From the photo the cable looks like a bicycle brake cable is it a stock piece of cable or a bespoke part?

It'll be a solid wire inner as it's a push/pull cable. A bicycle brake cable is stranded and no good at pushing.

I've got a solid cable where I had to finish the coiled end myself round a small bolt. It was for a Citroen heater air flap. Took the old cable to Cable Craft in Rathcoole to get something similar knocked up (http://www.cablecraft.ie/)

Dades

LIGHTNING wrote: »

Is it possible to just bodge that lever half closed? Even half the amount of warm air coming into the cabin would be nice! My car is like an oven!

Well, the lever in that pic was about 80 degrees counterclockwise from the position in that pic above before I moved it with my finger (it wasn't particularly stiff, either). I haven't driven the car yet to see whether (a) it moves back by itself or (b) it stops the flow of hot air. Will do so later.

If indeed having it in that position cuts off the heat a cable-tie might do until the weekend!

Also, I'd be very surprised if a standard bike cable didn't do the job to replace the cable if it comes to that.
EDIT - Just saw macplaxton's post. I hope you're wrong about the cable (or that I don't need one...!)

unkel

Same issue in my MGF - looks like the problem is very similar (others have reported it as a common problem). I should be able to access the cable / valve from the drivers footwell. Will investigate one of these days. Well, at least before spring comes

dharn

That cable is the same type used on lawmore throttles, may not be long enough in a porsche

Dades

Seemed to be still blowing hot after manually moving the lever... though possibly not as hot... and without the lever being held in place. Too bloody dark and wet to do anything but a cursory check!

Hoping to pull out the heater controls and cables this weekend.

Kenny Logins

dharn wrote: »

That cable is the same type used on lawmore throttles, may not be long enough in a porsche

Are you saying the 924 also pulled from the lawn mower parts bin? :pac:

dharn

Ya , of course the 911 has the briggs and stratton air cooled engine:D

Dades

Okay, so I've made things worse!

I tried unsuccessfully to remove the cable between the valve and the heater but the bastard wouldn't budge. In doing so I must have done something else because now - I suspect - I have a vacuum leak. When I fire her up there's no idle and engine splutters and revs with no consistency.

Am I right in saying the heater control valve is a part that could cause a vacuum issue (I have little experience with these things)?

I'm thinking at this point I'll have to replace it and the cable. And I can't drive it until I at least get the vacuum issue sorted.

deckie27

That is just a valve to allow hot water into the internal heater matrix.

you must of knocked of a pipe or something while working I the area.

Look for pipes going nowhere or ends that look like something should be there

Dades

I was wondering about a rubber pipe beside that disappears down into the engine bay that I thought seemed a little easier to tug than the others... I might need to get underneath to see where it goes. Maybe it's come loose.

If you reckon it's not an issue with the valve itself it has to be somewhere else.

macplaxton

TBH, it was probably best left alone until May next year!

Dades

macplaxton wrote: »

TBH, it was probably best left alone until May next year!

No way - I use the car all year round and am cold-blooded!

macplaxton

Dades wrote: »

No way - I use the car all year round and am cold-blooded!

Well at the start it was like an oven after 10 mins. You were misled by the unseasonally warm weather to make it cooler!

Just to rub it in, I've got the double luxury of an automatic heated driver's seat and a heater like a furnace - and fully controllable*





*it'll probably spring a leak/seize-up now I've cursed it...

Dades

macplaxton wrote: »

Well at the start it was like an oven after 10 mins. You were misled by the unseasonally warm weather to make it cooler!

Turns out I meant warm-blooded!

Managed to fix my vacuum issue... turned out to be easy enough to spot in the daylight. This obviously came loose when I was trying to get the bastard heater cable out. I can take the heat now I'm at least back on the road.



Away this weekend so the cable will have to wait another week.

salysol

Dades if you are looking into the engine bay from the passenger wing,take a large flat screwdriver and push the heater control valve lever over towards the drivers side as far as you can,you will need to put your left hand under the unit and hold the pipe while pushing,chances are the cable is kinked,i might have a cable here,will check on sunday if you think you need a cable !
hope that helps,incidently the heater on a 924 never stops working even when switched off it will send a light breeze.

Dades

salysol wrote: »

Dades if you are looking into the engine bay from the passenger wing,take a large flat screwdriver and push the heater control valve lever over towards the drivers side as far as you can,you will need to put your left hand under the unit and hold the pipe while pushing,chances are the cable is kinked,i might have a cable here,will check on sunday if you think you need a cable !
hope that helps,incidently the heater on a 924 never stops working even when switched off it will send a light breeze.

Thanks salysol.

The cable is currently disconnected from the lever. The odd thing is it's connected fine to the heater controls in the cable (I can see it's still hooked up) and I could also move it back and forward with the lever on the valve. It's as if there's two unconnected cables. But then I couldn't get the cable to come out of it's housing from the engine bay end. It was stuck fast.

I'm unlikely to get a chance to look at it this weekend as I'm taking the car away for a night. Really appreciate if you can dig me out a cable as obviously there's an issue there.

Do you know if the lever is pushed manually to the drivers side if that should cut the hot air out? Mine is currently cable-tied to the right and yet last night the heater was still producing hot air once the vents were opened. Would that indicate the valve might be shot, too?

Thanks!

salysol

Dades wrote: »

Thanks salysol.

The cable is currently disconnected from the lever. The odd thing is it's connected fine to the heater controls in the cable (I can see it's still hooked up) and I could also move it back and forward with the lever on the valve. It's as if there's two unconnected cables. But then I couldn't get the cable to come out of it's housing from the engine bay end. It was stuck fast.

I'm unlikely to get a chance to look at it this weekend as I'm taking the car away for a night. Really appreciate if you can dig me out a cable as obviously there's an issue there.

Do you know if the lever is pushed manually to the drivers side if that should cut the hot air out? Mine is currently cable-tied to the right and yet last night the heater was still producing hot air once the vents were opened. Would that indicate the valve might be shot, too?

Thanks!

The valve is probably ok ,which heater do you have,for example do you have the early heater which had 3 slide adjusters or the later heater which was much better it had the adjusters as well as a 3 speed fan switch ?
If you have the early heater even at the off position the fan will still run very slowly, you cant turn it off completeley.
I will have a look at my cables and see how the cable is connected to the control valve on sunday and get back to you Dades

Dades

My heater is the same as this one. It has a three speed fan alright.

Any other thoughts or assistance welcome.

salysol

Thats the later heater , much better than the earlier 1,i have a few of them will check tomorrow and see if i have the cables.

salysol

I have the cable you need Dades, but on closer inspection i would be surprised if your's is broken ,it's more likely to be kinked or loose ,which you should be able to fix,failing that it may be loose at the heater control valve,i also have the control valve, in order to check the cable properly you will need to remove the coil so you can see whats going on,don't disturb the wires on the coil , when you look at the heater control valve,you will see a clip holding the control wire make sure the outer casing surrounding the cable is secure,and the cable is moving freely.

Dades

Thanks for that.

Checking last week revealed that the cable seems to move freely at both ends. I could move the arm of the valve freely with the cable attached, and move the heater knob freely also - there just seemed to be no connection between the two.

But when I disconnected the cable from the valve and tried to pull it out from the casing it wouldn't budge. It'll be the weekend before I can find daylight to do some more tinkering.

The good news is the car did a 300km round trip this weekend without skipping a beat - even if it was a little toasty.