The No-Heat 930 - Questions

[16Volt]

86 w/'Auto-heat', B&B headers with heat



When I bought my car it came with squeegee to defog the windshield. I have tried every combination of HVAC settings and consulted the below pic and manual. Overall the heat sucks.

I think there may be multiple issues here but I can pinpoint one which is that there is no heat anywhere on the passenger side. I get a similar volume of air from the side vent and defrost vent but it is always cold. To my un-educated mind this would lead me to believe that it is not a blower problem.

I had the HVAC system checked out by two shops with the following results:
Shop 1 - stated that the drivers side flapper box was bad
Shop 2 - had inconclusive results, thinks the issue is with the auto heat controller

So I am open to other opinions/testing I can do.

Am I correct in assuming that the passenger flapper box would be responsible for heat on the passenger side?

If the car is cold and not running could I turn the key to start and select full heat to see if the flappers are moving? Or would the temp sensor for the autoheat system get in the way?


Helpful Related Threads - For folks with these issues down the road.
Help with 930 Heating Problem (Footwell Blowers) - Great thread showing the replacement of autoheat micro-switches
Autoheat and footwell blowers - Mostly folks discussing the SC system (not 930) but good info
weak link 930 auto heat? - Instance of servo arm failure
auto heat - 930 specific footwell blower info, triggering early turn on. Interior temp sensor info.
Auto heat Wiring - Interior temp sensor info, pics of autoheat controller
911 automatic heater control problem - Sparse info, 930 diagnosed as a SC. Info on Autoheat wiring.
Round heater dial should create BLAST of air from heater blowers. (If not, read this) - SC/Targa specific but good info on footwell blowers
Heater controls 101. Plus, I'm not sure windshield vent is actually working. - SC/Targa specific but good info on footwell blowers
Replacement footwell blower motor solution - Replacing footwell blower motors with cheaper AC blower motors
Caloric Feeler - Flapper box sensor
Auto heat sensor in flapper box? - Flapper box sensor

Here are some of my test results - no warranty expressed or implied

Factory Stated Fan Speeds (my observations differ, below)
Pos. 1-7 = Slow
Pos. 8-9 = Med
Pos. DEF = Fast

Pivot Arm Position at 60f Ambient
Pos. 0 = 3 o'clock (nearly, closer to 2)
Pos. 1 = 2 o'clock, No Fan
Pos. 2 = 1 o'clock, No Fan
Pos. 3-7 = 11 o'clock, Slow Fan
Pos. 8 = 11 o'clock, Med Fan
Pos. 9 = 11 o'clock, Med Fan
Pos. DEF = 11 o'clock, Fast Fan

Microswitches




Microswitch Activation
Position 0
Switch 1 - open
Switch 2 - open
Switch 3 - closed
Switch 4 - closed
Switch 5 - open
Switch 6 - open

Position 1
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 2
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 3
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 4
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 5
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 6
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 7
Switch 1 - open
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 8
Switch 1 - open
Switch 2 - closed
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position 9
Switch 1 - open
Switch 2 - closed
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

Position Defrost
Switch 1 - closed
Switch 2 - open
Switch 3 - open
Switch 4 - open
Switch 5 - closed
Switch 6 - closed

[jwasbury]

passenger side heat should be controlled by passenger side flapper box. You should be able to jack up the car, power it up and spin the auto heat dial and watch to see if the flappers are moving. There is a linkage in the auto-heat console between the servo motor and the mechanical lever that actuates the cables which open and close the flappers. Your problem could be with the linkage.

On my '79, it has auto heat, but there is also a manual lever that protrudes from the console. My autoheat linkage broke, but I prefer manual operation anyway. Maybe you can "backdate" to manual control?

at any rate, not sure how good the heat output is with B&Bs, but my SSI exchangers will burn your feet if you're not careful.

[Hams930T]

LOL!

Just wanted to say thank you for posting that picture. I've owned my car for a couple of years and the controls baffle me to the point of not using them at all. Seeing this pictures clears it up for me.

Anyhow - I hope you get your issues resolved.

Chris.

[spool930]

You may want to look at the rear blower relay, not cheap (haven't changed mine yet). From what I understand there are two blowers front and rear. My rear blower seems to work only when I don't need it. Tried it today and no luck because it's cold. I believe there is also a heat sensor that must reach temperature before the blower comes on. If you fine the answer please post.

I'm trying to fix mine today, 86 930.

[motorracer]

my 86 930 doesn't have a rear blower just foot well is the auto heat working

[krasuskyp]

yeah, 2nd'ing the ROFLMAO aspect of all ^this^!

I've studied the manual on the operation of the controls, then forgot WTF they all do again as time passed. Seeing that def makes me realize how basic it all is - and - that I will again soon forget it all... d'oh.

Further ROFLMAO... mine's been stuck burning my passenger's foot for years now... until... fall / winter hits, then NOTHING. Awesome.

I've got new cables to install (check those too, they can bind in the floor tunnel), and I'd installed a new dogbone linkage within the control box years ago but it just keeps popping off (something else is binding somewhere). The dogbone 'balljoint' dries up and cracks. The threaded rod must be an exact length - do a search here.

So, short story short - I live sans heat / defrost. Wear a coat 8-).

Oh, and my fresh air blower has decided to seize this year as well.

Sunnyday car! 8-)

ps. car came w/ squeegee... FTMFW! Hilarity...

[Ronnie's.930]

Originally Posted by spool930

You may want to look at the rear blower relay, not cheap (haven't changed mine yet). From what I understand there are two blowers front and rear. My rear blower seems to work only when I don't need it. Tried it today and no luck because it's cold. I believe there is also a heat sensor that must reach temperature before the blower comes on. If you fine the answer please post.

I'm trying to fix mine today, 86 930.

Originally Posted by motorracer

my 86 930 doesn't have a rear blower just foot well is the auto heat working

None of the 930 year models came with rear heater blowers (other than the primary engine fan, buttofcourse) or rear blower relays.

Now I hear that Paul is an excellent "rear blower", but that is an entirely different subject!!!

[Ronnie's.930]

Originally Posted by 16Volt

If the car is cold and not running could I turn the key to start and select full heat to see if the flappers are moving?

Yes, and when you move the auto heat dial off of "0", if you don't hear the servo moving (makes an easily heard winding sound inside the car), then nothing is happening with the flappers.

Originally Posted by 16Volt

Or would the temp sensor for the autoheat system get in the way?

No

[nickyclyde]

I have two cars with very similar complex hvac systems , an '87 Porsche turbo and a '90 vw vanagon. Both with confusing levers. Can never really figure either system out. I luck out sometimes and get the right temp , but im usually at my destination first.

[kenikh]

I know for a fact that b&b headers SUCK at generating heat. I drove my buddys car for almost 2000 miles with them (not a typo). Awful.

I was tempted to have Ben at M&K make a Y-pipe for SSIs or 993 HEs, until I realized that 3.2 Carrera HEs look identical to stock late 930 HEs and have a 38mm ID.

[Ronnie's.930]

Originally Posted by nickyclyde

I have two cars with very similar complex hvac systems , an '87 Porsche turbo and a '90 vw vanagon. Both with confusing levers. Can never really figure either system out. I luck out sometimes and get the right temp , but im usually at my destination first.

Nick, the only lever that controls heat temperature is the auto heat dial, or the manual lever(s) between the seats - they open the heat exchanger flapper valves progressively, and the further they are open the more hot air is sent into the car (as opposed to being blown out toward the ground beneath the engine bay).

The red lever on the dash controls the direction the hot air goes (if the flapper valves are open) - all the way to the left is the foot well vents and all the way to the right is the windshield vents (defrost). Anywhere in between and you get a mix between the windshield vents and the foot well vents.

[Hams930T]

Originally Posted by Ronnie's.930

Nick, the only lever that controls heat temperature is the auto heat dial, or the manual lever(s) between the seats - they open the heat exchanger flapper valves progressively, and the further they are open the more hot air is sent into the car (as opposed to being blown out toward the ground beneath the engine bay).

The red lever on the dash controls the direction the hot air goes (if the flapper valves are open) - all the way to the left is the foot well vents and all the way to the right is the windshield vents (defrost). Anywhere in between and you get a mix between the windshield vents and the foot well vents.

Ronnie -

Thanks for the simplistic description of the operation.

I drove my car today and was surprised for the first time that I couldn't stay warm. In previous cooler temp days my feet almost roasted from being so hot. Today; not so much.

On my autoheat controller - I typically drive around at setting 1-2 which is more than sufficient to keep warm. Today I actually turned it up to 5-6 to get warmer driving home but didn't have a lot of luck. I also noticed only a trickle of air coming from the side vents no matter how much I dialed up the auto heat. I took it to 9 and never noticed a change in air flow from the side vent. What is your experience on this?

My car sitting at idle would not really push enough heat to keep me warm in traffic driving home today, but was perfectly warm once moving. Strange.

Chris.

[T77911S]

i just went thru the controls and runnig my fans trying to figure what ran what and to make sure i dont burn my car up running the fans.

NOTE: my fuse block got to 160 degrees running ALL the fans at once. i cleaned the fuse and the fuse block (also clean the wire ends and the screw) and now it only gets to 102 degrees.

i need more info on the auto heat.
it only controls the footwell fans right
does it run the fans at the same speed in all positions. it seemed like mine came on only when in the red numbers. IE if the heat is on 3 are the fans on low
but then it sounds like a fan is running with everything off. when i start the car i hear a kind of loud "squeal" cominig from the front of the car.

[jwasbury]

Originally Posted by Hams930T

My car sitting at idle would not really push enough heat to keep me warm in traffic driving home today, but was perfectly warm once moving. Strange.

Actually that's not strange at all. As Ronnie described earlier, the primary "fan" that pushes air through the heat system is the engine fan, thus the airflow and heat output is directly correlated to engine rpms. On earlier cars like my '79, there are no electric fans helping to push air through the heat ducts, I only have the engine fan. Heat output at idle isn't very good as a result.

I'll reiterate that if you want really good heat, the SSI exchangers are second to none. If I pull the heat lever to the maximum, the heat output is practically unbearable. It's also nearly instant...the exhaust gets hot very rapidly even after a cold start. You do have to keep rpms up to cruise level, between say 2500-3000 rpm.

While the 911 hvac controls are indeed unique and quirky, I don't believe they deserve to be elevated to "mystical" levels that seem to persist on the forums. It's really pretty simple, and especially makes sense one you realize that the heat system is completely independent of the fresh air and A/C portion. You can run both heat and A/C simultaneously, and have them "fight" with each other (heat wins hands down in my car). I do run the A/C same time as the heat in my car when I'm trying to get maximum defog as the A/C actually pulls moisture out of the cabin.

[T77911S]

mystical? maybe not. but in the electronics world we have a saying for things like this.
FM.
F@@ing magic.

its like it has 3 seperate systems in the car. the diagram above pretty much sums it up.

[Hams930T]

Originally Posted by jwasbury

Actually that's not strange at all. As Ronnie described earlier, the primary "fan" that pushes air through the heat system is the engine fan, thus the airflow and heat output is directly correlated to engine rpms. On earlier cars like my '79, there are no electric fans helping to push air through the heat ducts, I only have the engine fan. Heat output at idle isn't very good as a result.

I'll reiterate that if you want really good heat, the SSI exchangers are second to none. If I pull the heat lever to the maximum, the heat output is practically unbearable. It's also nearly instant...the exhaust gets hot very rapidly even after a cold start. You do have to keep rpms up to cruise level, between say 2500-3000 rpm.

While the 911 hvac controls are indeed unique and quirky, I don't believe they deserve to be elevated to "mystical" levels that seem to persist on the forums. It's really pretty simple, and especially makes sense one you realize that the heat system is completely independent of the fresh air and A/C portion. You can run both heat and A/C simultaneously, and have them "fight" with each other (heat wins hands down in my car). I do run the A/C same time as the heat in my car when I'm trying to get maximum defog as the A/C actually pulls moisture out of the cabin.

Hi Jacob,

Thanks for the response. You're quite right in that the system is not overly complex once you understand the purpose of the controls and they are operating independent systems. I drive 95% windows down fresh air so the only time I've used the controls has been in the winter when it is colder and I would like some heat in the cabin.

My car is moving hot air for sure at cruise. I tested it this morning on my commute with the heat set at maximum on the Defrost setting. It was warm but not unbearable. I noticed no additional airflow and I suspect the footwell blowers are INOP. I clearly hear the servos running to turn the flappers under the car and I am getting heat; just very little "flow". Checked my fuse #10 this morning before leaving to verify it is good. To date the car has never had any electrical gremlins thank goodness. I'm going to dig a little deeper. Frankly in Texas heat isn't needed very often. It just happens to be in the 30's at the moment and I do like to be toasty as I'm blasting down the highway on my commute!

Chris.

[tailwind22]

I am troubleshooting my BB Header heat system on one of my 930s also. Determined last night that my heat control servo was indeed working but failing to move the cable to the flappers. I will next remove the passenger seat and the inspection cover on the heater control to view the movement of the linkage by the servo. I suspect a hang up in the cable and or linkage as some have commented.

[Hams930T]

I guess if I was smart I would have checked out the heater to make sure everything was operational before it got cold. Oops!

[Ronnie's.930]

Chris,

I don't know how much hot air should typically come out from the side vents as I don't use them for heat, and in fact, have blocked off the hot air feed that comes to them from the foot well blowers (I removed the small duct that runs between them and the foot well blowers and then capped all of the associated spouts with aluminum tape). I did this because I really hate having hot air blowing on me, regardless of the outside temperature and I didn't want even the slightest bit of my precious a/c air leaking into those ducts.

And yep, the hot air movement at idle is basically just a trickle if the foot well blowers are not working. Mine are also INOP (motors are seized) and I have never repaired them since I do not need much heat to keep me happy. In fact, in weather like we are currently having in TexASS, I run the heat dial on #3 or less (usually #s 1 or 2), and have the sunroof about 1/2 open at all times (including on the highway). I'm a freaky freakazoid, I know!!!

[Hams930T]

Originally Posted by Ronnie's.930

Chris,

I don't know how much hot air should typically come out from the side vents as I don't use them for heat, and in fact, have blocked off the hot air feed that comes to them from the foot well blowers (I removed the small duct that runs between them and the foot well blowers and then capped all of the associated spouts with aluminum tape). I did this because I really hate having hot air blowing on me, regardless of the outside temperature and I didn't want even the slightest bit of my precious a/c air leaking into those ducts.

And yep, the hot air movement at idle is basically just a trickle if the foot well blowers are not working. Mine are also INOP (motors are seized) and I have never repaired them since I do not need much heat to keep me happy. In fact, in weather like we are currently having in TexASS, I run the heat dial on #3 or less (usually #s 1 or 2), and have the sunroof about 1/2 open at all times (including on the highway). I'm a freaky freakazoid, I know!!!

I am typically running my heat on 2-3 with the windows down. I like the fresh air and the sounds. I guess over the past couple of days I definitely noticed the heat wasn't keeping up at a trickle. I am pretty certain my footwell blowers are INOP. I haven't started any diagnosis yet but I spent a good portion of my day at work reading up on the subject (instead of working....)

Oh well- she's about to go down for my spring project anyhow!

Chris