911 3.2 How does the heating system work??

[dave99]

Hi All,
I have my 911 3.2 for 6 years and mainly drive in the Summer. On the occasion when I get caught in a shower of rain or when I have to drive it in the Winter, how does the heater work??

I have been looking back over old posts but cannot find an explanation. My cabin is always hot once the engine warms up and I can not direct air flow. I also cannot make sense of the heater controls as they appear to do nothing

I see there is a fan in the engine bay for the heater system. Should this come on when the heater is switched on?

Thanks in anticipation for your help,
Dave

[p-cardriver]

There is no simple explanation that is also comprehensive.

Start with the two red levers between the seats. If they are down on the floor, the heat should be off. The rotary switch between them should be a "0" to be off as well.

Raise the driver's side lever to increase heat to that side of the cabin. Guess what the passenger's side lever does???. The rotary switch can increase airflow via fans.

On the instrument panel (aka dash), the levers are used to direct heat to the floor or windshield as needed. Other levers there introduce outside air into the cabin. And if your car has A/C, that is in the console and a third, independent system.

There are some posts here with a lot more detail and pics of the levers, switches, etc.

[pete3799]

[Dublinoh]

Also auto climate control was an option...so you may have the auto heat controller and as far as I can tell on my car it doesn't do much...the function comes from the other controls. Pete3739 has provided the best over view.

Simple answer for heat pull up both red levers between the seats the higher you pull them the more heat you get...you may have fans below the dash on each side and you will hear them come on. red lever on the dash controls heat up to windshield (R) or down to dash and under dash (L). Heater fan in the engine bay should come on too, but I can't hear it in the cabin.

If you can not control heat on/off you heater valve boxes are stuck and not opening and closing. A common problem because they do rust. You may be able to lubricate and work them loose so the function again or replace them. They are at the forward attachment of the front hose on your heat exchanger.

[dave99]

Thanks Lads,
This Forum is a mine of information. Really appreciate your help. Don't think my fresh air fan is working... and don't recall seeing two red levers between the seats. There is a rotary switch though..

Looked at the heater valves before and they look a bit rusty.

Thanks,
Dave

[wrxnofx]

Dave,

I know this topic has been covered many times, so use the search to help learn more.

With that being said you have the same system as I do with the knob only and no red handles. This system is called autoheat.

To test, you don't have to start the engine. Simply turn the key to position 2. You can then turn the autoheat knob to the highest number, which is 10 I think. In doing so, the engine blower fan should come on (it bypasses the cabin sensor if memory serves) and the flappers should close.

If the blower doesn't come on, then the problem could be within the autoheat box between the seats (there is a rod that comes detached which could be one problem, or the circuit board could be fried). The problem could also be the relay in the fuse box in the engine compartment. The problem could also be the blower itself.

A prerequisite to the footwell blowers in the cabin by your feet turning on is that the engine blower fan must turn on. If you eventually get the blower fan to turn on but not the footwell blowers, then check the inline 10AMP fuse that is located near each blower to see if those are blown. There is a way to bypass the engine blower by bridging something in the relay back there, but you'd have to search for this (people do this when they backdate the heat in the car and remove the engine blower, letting the footwell blowers provide sufficient air movement to the cabin).

If your cabin is always warm, it could be that the flappers are stuck closed, thereby letting the heat be directed through the plumbing into the cabin regardless of whether the autoheat is turned off. None of my blowers turn on when I turn on my autoheat and I haven't had a chance to figure it out yet. But when I do turn it on I get just a pinch of heat eeking out of the vents, making me think that my flappers at least close and open properly.

[Nick Triesch]

Possibly the worst heating/ventilation/AC system ever installed in a car! Blowers on top of more blowers with tiny vents and levers and blowers! After 3 years I still just pull levers to get heat. Even a Yugo put cool air on your face! And that was the worst car ever made!!

[wildthing]

Minor correction on the pic, center console arrows. I think that's the hazard lights on the left and defroster on the right. The A/C controls are below those two.

[rokemester]

Originally Posted by Nick Triesch

Possibly the worst heating/ventilation/AC system ever installed in a car! Blowers on top of more blowers with tiny vents and levers and blowers! After 3 years I still just pull levers to get heat. Even a Yugo put cool air on your face! And that was the worst car ever made!!

Forced to agree. My 66 Bug delivers just as much heat more directly than my 87 Targa. I've been trying to swap out the various sensors and swap circuit boards etc. etc. and still can't get the autoheat to cycle on and off to automatically adjust the temp. I end up manually reaching in through the console opening and moving the heat valve lever.

Just search the forum using the term autoheat and you'll find plenty of excellent troubleshooting approaches.

[HarryD]

To lighten the mood:

Originally Posted by HarryD

Thanks to RWebb, we do have the factory explaination as well :

It goes like this:

"There have been several questions about this recently, so I thought I would post the Official Factory Explanation:

Subject: RE: Heat Control FAQ for Pooschey


Q: I just bought a Pooschey 911 and can't figure out how to make the heater work -- or the fresh air either. Can you help me?

A: Sure, I can help you. The ventilation system requires that you operate 4 levers to make it work. 3 of the levers are on the dash, and the other is between the seats on newer Pooscheys there are 2 levers between the seats).

The top lever on the dash actually does several different things (remember, it is a fiendish German device, just like the rest of the car). Pushing it to the middle opens the dust ports leading to the windshield (see below for operation of fogging machine and oil mist spray device). Pushing it to the right past the middle also activates the rattling noise-maker device. There are three loudness levels to choose from. Pushing the lever all the way to the left is used to jam the cable so unauthorized personnel cannot operate any of the devices above. The lever also enables the automatic heat exchanger signalling device -- when opening it spews rust particles on the windshield, you should replace the heat exchangers. Also, if opening it causes you to immediately turn blue or purple (not just hair, but skin color) and become unconscious, you (or your estate) should definitely replace the heat exchangers.

The second lever from the top controls the lights on the White House Xmas tree. Move it to the middle to turn on the lights, and all the way to the right to fire 4500 Megatons of Nukes at Iraq.

The bottom lever on the dash is used to replace the windshield when it becomes scratched or pitted with rock chips. It also determines how much hot air goes to your feet as opposed to your head. For example, let's say the engine is completely warmed up and the hot air is burning your feet. If it's a cold day, you can flip the lever to the other side and shoot hot air onto the windshield so it cracks and shatters. Then call your insurance company (you do have insurance, don't you?)

The lever between the seats controls the oil mist spray device. When the engine is warmed up, this lever allows you to blow oil mist into the passenger cabin. Using the top dash lever lets you select whether you want the oil mist to coat the inside of the windshield or to just circulate around your feet. On a newer Pooschey, you have 2 levers on the floor between the seats. The left hand lever lets you open the left side vents which are aimed so they burn the feet of the person in the right hand seat, and the right hand lever lets you open the right side vents which are aimed so they burn the feet of the person in the left hand seat. Of course, each lever will also burn just the tops of the feet of the person in the other seat. If you are driving in the rain (or even stopped in the rain after the car has broken down), these levers also let you spray a fog of water vapor on the windshield, so no one can see in or out of the car -- sort of like privacy glass."

[dave99]

I like that a lot!!!

[dave99]

Hello All,

I have switched the ignition to #2 and turned the heater to 8. I have no fans coming on at all.
I removed the fan in the engine bay and it works with a battery.
Could you please post a pic of the relay so I can find and check it?
Thanks,
Dave

[yelcab1]

All so simple, no ?

[motogman]

The short answer to the original question....

"How does the heating system work?"...


Not very well.

[dave99]

Originally Posted by motogman

the short answer to the original question....

"how does the heating system work?"...


Not very well.

:d:d

[wrxnofx]

Originally Posted by dave99

Hello All,

I have switched the ignition to #2 and turned the heater to 8. I have no fans coming on at all.
I removed the fan in the engine bay and it works with a battery.
Could you please post a pic of the relay so I can find and check it?
Thanks,
Dave

If you have the full autoheat (i.e. no red levers for flappers) you have to turn the heater position to the defrost position (i.e. 10) in order to bypass the sensor if memory serves. At this point you can check for 12 volts at the motor connector. You should have it.

The relay is in the engine compartment fuse box behind the black panel on the driver's side. I don't have a pic handy but I want to say it's the left one. Searching for other threads on autoheat will find you the pics, although I don't know of a way to troubleshoot the relay other than jumping it to see if the footwell blowers work (again, use search for this).

[T77911S]

i can build a porsche engine, i can fix several versions of radar used to control air traffic, i can build things with wood, i can buid things with steel. i can fix CIS for 911's and 930's. i can fix wiring problems, i can fix communication systems used with air traffic and various other systems. but i will be damned if i can figure out the heat/air systam in a 930.

[dave99]

Originally Posted by wrxnofx

If you have the full autoheat (i.e. no red levers for flappers) you have to turn the heater position to the defrost position (i.e. 10) in order to bypass the sensor if memory serves. At this point you can check for 12 volts at the motor connector. You should have it.

The relay is in the engine compartment fuse box behind the black panel on the driver's side. I don't have a pic handy but I want to say it's the left one. Searching for other threads on autoheat will find you the pics, although I don't know of a way to troubleshoot the relay other than jumping it to see if the footwell blowers work (again, use search for this).

Cheers for that wrxnofx

[dave99]

Originally Posted by T77911S

i can build a porsche engine, i can fix several versions of radar used to control air traffic, i can build things with wood, i can buid things with steel. i can fix CIS for 911's and 930's. i can fix wiring problems, i can fix communication systems used with air traffic and various other systems. but i will be damned if i can figure out the heat/air systam in a 930.

so its a minefield then!!!!

[ClickClickBoom]

Originally Posted by motogman

The short answer to the original question....

"How does the heating system work?"...


Not very well.

My 3.2 with SSIs goes from cold to hot to pissed off dragon heat in 1.63mm of lever travel. I would say it works too well. The A/C, works great too, open left or right window or the sunroof.