francesconyc

So, I finally located a strange noise I was hearing from the back and it was the heather fan.
To detect it, I simply remove the heather fan relay on the back and the noise goes away.
Now, if I remove the relay and the motor stops, I notice a smell of plastic burn, that goes away if I put back the relay on his position.
Maybe is it a coincidence, but is it possible that the heater fan has other duties in the car?

Also, do you know if the heather fan is always on?
or does it go on if you turn the defroster on?
(in my car I have that weird **** by the brake lever with the temp nipple sensor on the roof)
I have no idea if the PO of my 82' SC was using the heather (I think he never drove in winter/snow/rain) so probably he never noticed
also who knows if that **** even works... I hear some strange noises when i turn it down to 0

Mark Salvetti

So with your car, you have autoheat with the **** that has settings from 0 to 10? The fan in the engine bay runs if that **** is set to anything other than 0.

There are two flapper boxes under the car (in front of the engine) that open and close depending on whether you are asking for heat in the cabin. Most of us have manual heat, with two red levers where you have the control ****. Pull the levers up and the flappers open (via a cable) and the fan in the engine bay turns on.

The auto heat system has a servo motor that operates the cables to the flappers. When you turn the **** to zero, the motor is probably trying to close the flappers. They may be rusted stuck. Or the actuation rod popped off the motor.

Mark

francesconyc

Yes my car the auto system

i didn't know there was a servo for flappers, that may explain the whirring strange noise then i set the **** to 0

if your is manual does it mean the hear blower is always on, and the flaps are th only thing to prevent hot air to come inside the cabin?


What I'm asking is if i can disconnect the motor for now until i will install a new one (i juts ordered the motor in pelican)

francesconyc

This is the video of the motor
engine is off
Only battery is on (ignition on on the key switch)

I probably had the heat set to above 0
but i have to check again as I didnt know about it

oldskewel

You can just unplug the heater blower motor. Its purpose is only to blow air past the exhaust heat exchangers up to the cabin for further blowing and distribution.

That is a common failure.

In general, the HVAC systems in these cars (mine is an '85, so is different - and that's another challenge when trying to learn from other people; mine is manual, but automatic became standard soon after '85) are more complicated for the user than in most cars. So, it's probably worth some effort to figure things out. That will help both with knowing how to use it and in figuring out what parts may be broken. In my car, I think the front blower motors (in the L+R footwells) both failed as well.

francesconyc

so, I tried today to unplug the blower
(to be fair, I also tried in the past a couple of times), and I every time I unplug it, sure the noise thank god goes away, but I start noticing some smell of hot plastic in the cabin,
again, it maybe a coincidence but today a friend of mine was my passenger and he noticed the same

also we noticed some random light smoke? / vapor? from the ac vent? has the same smell as you would feel when you smell the exhaust...

So, I'm wondering if the role of the blower is not only to channel hot air from the engine to the cabin but or also to remove hot air from the engine and keep it fresh
I think the plastic smell could be coming from the black plastic hose from the blower box which gettign very hot because the blower is off and stop the hot air right there...

Anyway, it's hard to troubleshoot now:
I still don't have the answers:

• IS the heat blower fan always on as soon as you turn on the ignition? can nay body please check?
• OR the fan is activated concurrently with the ****?
• does the heat blower have only the role of heating the cabin?

not my car, just an example

Mark Salvetti

OK, as I said in my response a couple of days ago, with your auto heat, the blower in the engine bay is off if your **** is set to zero. It turns on at any other setting. If you had manual heat with the levers, the blower is off if the levers are down, and only turns on if you lift them up. The only purpose of the heater blower in the engine bay is to provide heat.

The corrugated duct to the blower is the suction. It is pulling hot air from under the engine shroud. There are two hoses leaving the blower (one is #2 in the photo above). Each of these hoses goes down through the engine tin and connects to the heat exchangers near the rear of the car. The hot air sucked from under the engine shroud is pushed through the heat exchangers, where it gets even hotter. The hot air exits the heat exchangers through hoses towards the front, and passes through the flappers. These are closed if you have the heat off, open if you have heat on. If the flappers are open, the hot air passes through hoses in each rocker to the dash.

Read this: https://www.pelicanparts.com/techart...tem_Repair.htm

I think auto heat functions by adjusting the flappers. There is an inspection door on the auto heat console facing the passenger seat. You can look inside and make sure all the cables are connected and moving.

I doubt the odor is from the hose overheating. More likely coming from a problem with the fresh air blower in the front trunk, by the wipers. Is it running? On the dash there are four sliders. The one at the top right controls the fresh air blower. I think the blower is off if the lever is in the middle setting, moving it right speeds up the fresh air blower.

Mark

francesconyc

Thank you Mark always very thorough!
I'm only a month-ish old owner so I'm still learning to "auscult" my car.

this is what happens in my car:
- when I turn the key ignition ON (position 1, not start 2) the rear heat blower starts running immediately. This may be due to my auto-heat **** not working properly –(my **** suspiciously spins 360 so who knows if it goes to zero...)
- my flapper lever is all pushed down... but god knows if it's working or not (PO didn't know much, as he was a summer driver only)
- my auto-heat **** is set to zero, but the plastic also spins all around so maybe who knows if is set to zero
- the temp sensor nipple on the roof is there, I guess it doesn't matter to troubleshoot it yet.
-my fresh air fan works (noisy but works)


What to do NEXT
I guess to troubleshoot this I should do the following (and let me know if I'm missing something)

1. remove the fuse for the AC blower, so at least i remove a variable from the picture
Question: are all the ventilation ducts connected or the AC has separate ducts never mixed? my ac fan but doesn't seem to work but this is will be addressed in another "episode"
2. maybe remove the fuse for the fresh air. again to have less noise and other variables to confuse me
3. check under the car if the flappers are working or not (open/close)
Question: how do I get under the car? can I inspect visually lying down or do I need at least a ramp?
4. remove/disconnect the auto-heat box between the seats, and check if the potentiometer/switch is working mechanically first
Question: I can use a multimeter here I guess... anything I should check specifically? voltage etc?
5. replace the motor. this is no doubt something I need to address ASAP because the noise is unbearable at this point

am I missing anything?
essentially I want to at least understand
-why the rear blower start running immediately,
-why do I feel it smells like hot plastic (does the rear blower provide any cooling effect on the ducts?) - this smell could be coming from the AC vent by any chance? I may be correlating wrong things happening together...

Mark Salvetti

Something is definitely wrong with the auto heat controller. Sounds almost like the **** is disconnected, it shouldn't spin like that. I'm sure that is why the heater blower turns on all the time - the broken auto heat **** is set at something other than zero. You'll have to open up the box and see what is going on in there. Sorry, I don't have auto heat, so you'll have to try searching. You can target a Google search like this:
Rennlist: Porsche 911 auto heat repair
Pelicanparts: Porsche 911 auto heat repair

You'll get search results mostly from the forums. You may need to try different search terms after the colon.

• You'll find the front AC blower (in front of the fuel tank) is not fused. One of those German electrical mysteries (like no fuse on the instrument lights).
• AC is not separately ducted, other than a vent under the dash I believe. Sorry, I don't have AC.
• You probably won't be able to get far enough under the car to do much with the flappers without jacking the car up. Sounds like you have the auto heat with the red lever? That is a backup for emergencies, it is normally down. But if you have a helper and they pull up on the lever, you should see the flappers close. Just remember never to just use a jack to lift the car if you are getting underneath. Always use jack stands, ramps, or a proper lift.
• Definitely try pulling the fuse for the fresh air blower behind the dash and see if you still smell plastic or see wisps of smoke coming out of the dash vent (which one by the way?). Wisps of smoke is a very bad sign and not likely coming from the engine bay. Be very careful with this, you don't want a dash fire.

Mark

francesconyc

About the heat:
yes, something is wrong with auto-heat
also, I remember that it used to make a whirring noise when moved from 0 to another number (probably a servo to open/close the flappers?)
I ordered a new ****, and worse scenario I found on eBay the entire heat box for $380

since I had the car I have never been able to get air blowing hot air, other than a very faint hot air coming from the sides, which can explain the almost dead motor

(I will check the flappers when I get to a friend with tools in spring and I can jack it, do a bit of maintenance, oil, brake pads etc)

About the AC:
btw, my user manual reads the AC blower has its fuse (position 20 blue 25AMP)

this makes me think that I replaced it at the same time I disconnected the heater motor, which was the first time I felt the smell...which led me to think the smell was due to the non-running motor and not the AC

the ***** of my AC don't do anything not even warm air (i tested with a friend listening close to the smuggler box but no change in noise if i rotate them back and forth — i have no freon to test it properly btw)
...so maybe the AC is seized?? HENCE the burning smell and a whirring noise from the front?
I better remove that fuse!

francesconyc

yes I do have only one red lever

I wonder if I can simply try to "feel" the flappers (without jacking for now) with my arm hand/to see if they are open or closed.
or maybe just take a picture with my iphone...

I cant find images of their exact location though...seem near the sruts??

if they won't close, then i can buy new ones and plan to get on some ramps/stands

Mark Salvetti

You know, I think you can see the flappers if you remove the rear wheels. Look up and in front of the rear shock absorbers. Some photos and rebuilding tips here. They can be pretty badly rusted: http://forums.pelicanparts.com/porsc...per-boxes.html

That fuse you highlighted is actually for the evaporator blower inside the smugglers box. The factory didn't fuse the front AC condenser fan (in front of the fuel tank) until 1987 or so.

Mark

francesconyc

Thanks Mark (you are a living Porsche encyclopedia),

those pics of the flappers are more clear… I could try reach with my phone to take a photo or jack the car and take a photo (i might even have a boroscope for plumbers somehwhere!)). Ultimately i only need a confirmation the cable on/off works or not– for now.

for the AC, maybe I don’t understand how it works, but in my car –inside the “smuggler” box – there is a black housing for what i think is a fan, right? Are you saying there are two fans?
Either way, I think the smuggler blower is what is pushing cold air into the cabin right? if so then it may be the cause of the light smoke/smell.
If I understand correctly (maybe not haha) the front condenser fan is to lower the temperature of the condenser?

I’ll start removing the fuse and see if it stops (also stop the whirring noise)


(now I understand why people delete the AC. so many parts to maintain for so little benefit, ugh!!!)

Mark Salvetti

You have at least two blowers in the front trunk and probably three. There is the blower for the evaporator in the smuggler box. The evaporator is where the liquid refrigerant is allowed to expand, turning it to a gas and lowering its temperature. The blower forces warm air through the evaporator heat exchanger. This cools the air and then it enters the cabin through the dash vents and through a vent under the dash.

The vaporized refrigerant is now warmer (having picked up heat from the air that it cooled) and now the refrigerant needs to be cooled so it condenses back to liquid before it goes into the compressor. A 911 with factory-installed air has two condensers to cool the refrigerant and turn it back to liquid. One is under the grill on the rear deck lid. Air is pulled through that by the engine fan. There is also a small condenser in front of the fuel tank. There is a blower there, forcing air down through the condenser to provide cooling. You can see the condenser from under the front of the car. This is the second fan in the front trunk, and the one that is not fused.

If you have dealer-installed AC, you won't have this front condenser. My car didn't have one. I only had a condenser under the rear deck lid.

The third blower is under the front cowl by the wipers, and behind the fiberboard blower cover. This blows fresh air into the cabin, and is independent of the AC system. I think there is a good chance your plastic odor is coming from this blower.

Mark

francesconyc

(I have no idea who installed the AC but my model seems to be SC with a sport "package": rear spoiler whale-tail, front spoiler, and I guess AC/ and auto heat were part of it, maybe)

The fresh air blower in my car seems to work, it's noisy but it will push fresh air without any smell. and when I turn it all down (actually lever all to the left)
the air stops completely.

I saw with my eyes a faint smoke/vapor from the central vent, that's why I think the AC could be the culprit.

anyways, I will do all these tests on Saturday and report back