No Heat for BUTZI!

[racerpaul]

Well.. time to troubleshoot the heater system. Not getting any hot air after setting the controls for heat.

Looks like the thermal reactors / heat exchagers are in good shape as per exterior inspection... what do I check for next, would like to get a look at a manual or something. Wil search the net, maybe some hints?

[Dave L.]

Paul, I did not find any useful description of the heating system in my 912E Workshop manual, but did find more info in the Porsche Workshop Manual 911- from model 1972 on. Essentially you have three things going on with the heat in a 912E: a cable operated pulley from the cockpit to L and RHS variable fresh air flaps; an electrically operated blower motor ducted through air hoses which pushes warmed air forward into the cabin (it turns on when you pull up on the heater knob(s) next to the handbrake; and Heat Exchangers which simply 'capture' heat from exhaust header pipes and make the warm air available to the blower to be pumped forward to the cabin- all of this vented through various wide bore hoses. You vary the amount of heat by simply pulling on the cables which attach to the fresh air flaps, thus- pull up all the way- close flaps and just warm air; or- halfway, a mixture of hot and cold, etc. A very simple virtually all mechanical system- almost independent of the second fresh air blowerr (winscreen/cabin dash vents), since the heat reaching this furthest point forward takes a while to arrive! Right! Now that you're as confused as I am- good luck! TRy a Haynes 911 Manual too, it may have more. R/Dave L. #496 and #979, etc.

[racerpaul]

Very helpful Dave, Thanks... you've given me a great breakdown on how I will proceed in attempting to get some warmth in the cockpit. The frost is not yet on the pumpkin here... but it's coming!

Thanks ... will keep you posted.

[racerpaul]

Looks like the fan motor isn't working, checked the fuse, it's ok. Found what I think is the switch near the heater handle on the floor. Need a wiring diagram and will ring it out. Anyone know where to get a wiring diagram?

Thanks

[76912E]

Paul,

Try here:

http://www.texas912.org/912E%20Tech%20Data/912E%20Wiring%20Diagram%20pg%201%20of%202.pdf

and

http://www.texas912.org/912E%20Tech%20Data/912E%20Wiring%20Diagram%20pg%202%20of%202.pdf


Fran

[racerpaul]

Thanks Fran, that realy helped! I tracked it down to the micro switch at the heat / defrost lever, got the fan working.

But now it seems like there is no heat cominup from the thermal reactor...got to check the cable and lever action, maybe the control isn't opening... just not sure where the cable goes. Any diagrams? I've searched here... so far no luck.

[quickr-2]

Hello; When the cable breaks on 911/912's the heater valves coming off the exchangers close automaticaly. My everyday driver #627 just did this,till I get a cable I just wired the valves open[Its cold out now anyway] Warmest Regards;Chris

[racerpaul]

Good Idea! Wiring the vents open.

So I guess I need to crawl under the heat exchangers ( I thought they were Thermal reactors?) and check the vent flap? It seens like the cable is moving with some resistance but I'm not feeling any heat com up to the ducting at the blower

[quickr-2]

Hi Paul; Jack up the rear of your car and pull off the rear tires,you will see the heater flaps there.[Hose run up from the exchangers to the flaps.] Flaps are affixed to chassis,with three nuts.[The flaps do rust/rot after the years] You will see a spring on the flap valve,when the cable breaks it causes the flap to close. Its one of the easier things to work on,on a Porsche. Warmest Regards;Chris

[racerpaul]

Thanks again for the quick reply Chris.

Is there a difference between the 'thermal reactors' and heat exchangers?

I was under the car this afternoon and I see a duct hose coming up from the muffler / reactor / exchanger area and the hose runs directly up into the engine compartment wher it mates with the hose that runs to the blower motor...?? Can you tell I'm confused? Sorry maybe it's the thermal reactor thing thats got me mixed up. Is there a diagram / illustration somewhere?

ps... there seems to be no heat comig up thru those hoses.

[quickr-2]

Hi Paul; What your looking at is the inlet for the fresh air from your engine compartment blower motor. The blower forces air down into your heat exchangers. On the opposite end of each heat exchanger,you should see orange hoses running up towards your flaps. The set-up is easy to see if you remove your rear tires. If you are having trouble,I can remove a tire off mine and snap a couple shots of set-up later in week. Warmest Regards;Chris

[racerpaul]

Chris... you're the best!

Thanks for clearing this up for me... all the while I thought those hoses (which are kaput) was where the heat comes from!

I probably won't be able to work on Butzy 'till Saturday or maybe late Friday... I'm using the 912E as a driver lately being that my other ride(s) include two Trans Ams 89 and 90 Ttops and Convertible that the wifey an 19 yr old college boy use... a 1977 Formula Firebird with 45 k original one owner car and a Excursion (passes everything but gas stations! (The Excursion is my normal ride) ... the 1969 VW bug with 14k orig miles is only allowed out on weekends (wifey's orders).

Not so cold here yet, but I gotta get it fixed soon!

Thanks again for the help... I'll keep ya posted.

[eki912]

As all the others have already mentioned , the "heating system" in a 912 E is so simple , that when you figure it out , you will laugh....
But nonetheless it works just the way they described.
The engine fan , and the electrical fan in your engine bay force air down through the engine tin.Towards the heat exchangers , via the short lenth of tubes between the engine tin and heat exchangers.Naturally the heat exchangers are also fitted to the enginefan case.You do have those 2 small covers underneath the fancase,where it mates the heatexchangers?
Then this air should move through the heatexchangers towards the cabin end , on top of heat echangers hoses pointing up , connected to these wire driven heat valves (or what ever they are called ) with a flexible hose , and then from there towards the cabin.
It is kind of confusing as in a Porsche , hot air from engine is forced from rear end of the car to the front...check those hoses and those valves.

[racerpaul]

eki912, Thanks for the input... and yes... laugh I did!

Have not had a chance to get working on it yet and today it's pouring and thundering.

Will keep ya posted.