Heater is blowing weak

[polizei]

Hey Guys,

I did a search but couldn't find a thread that speaks to the issue I'm having. The heater in my '87 Carrera isn't working right. When I turn on the heat controller that sits between the driver & passenger seats, I hear some noises and feel a very light flow of heat coming out of the side vents. As I move the dial from 1 to 9, I don't feel any difference in the volume of heat coming out.

I've confirmed that my engine compartment blower is functioning fine, and since I'm getting some heat into the cabin, I assume there's no problem with the heat exchanger ducts & valves. Do you think my footwell blowers have died?

Thanks!

[86 911 Targa]

Andy,

Have a look at the flappers.

They may be stuck partially open.

Gerry

[polizei]

Originally Posted by 86 911 Targa

Andy,

Have a look at the flappers.

They may be stuck partially open.

Gerry

Hi Gerry - Thanks for weighing. If the flappers are partially opened, would that explain why I'm barely any airflow is felt coming out of the side vents at position 9? If it were just a flapper issue, I'd expect to feel a good amount of air being pushed out at position 9.

Thanks!

[86 911 Targa]

Originally Posted by polizei

Hi Gerry - Thanks for weighing. If the flappers are partially opened, would that explain why I'm barely any airflow is felt coming out of the side vents at position 9? If it were just a flapper issue, I'd expect to feel a good amount of air being pushed out at position 9.

Thanks!

Not sure I understand your response.

However, have a look at the flappers while some-one else
runs the heat.

Gerry

[wrxnofx]

If the blower motor in the engine compartment is actually working and you're getting virtually no air in the cabin I'd suspect the flappers, too. Since you mentioned position 9, you must have autoheat. Therefore, it's possible that the servo motor in autoheat box doesn't work or the arm connecting the servo motor to the linkage fell off.

As Gerry suggested, lay under the back of the car so you can see one of the flappers. Then have a friend turn on the key and turn the autoheat knob to 9. You should see the flapper valve rotate the open holes closed (which is also opening the corresponding valve plate inside the flapper housing, allowing air to flow fully into the cabin).

Regardless of whether the footwells are seized or not (which you can easily check by removing the kick panels), there should be a decent amount of air flowing into the cabin at position 9 on the autoheat dial.

[strikee]

Also check the ducting is actually connected to the top of the flappers. It might of come off, partially or completely.

[jlex]

I had to replace the control link that goes between the arm of the servo motor and the cable link to make the flappers actuate on my '85. That link is inside the box where your 1-9 heat control indicator is located. There's a little door on the passenger's seat side. Open that door & you'll see what I'm talking about. When mine was broken, I could hear the servo motor operate, but it's arm was unattached due to the broken link. If the link's kaput, the flapper boxes won't receive the signal to open. IIR, I took the passenger seat out to repair it for more room although you can struggle with it if you elect to leave the seat in.

[86 911 Targa]

Originally Posted by jlex

I had to replace the control link that goes between the arm of the servo motor and the cable link to make the flappers actuate on my '85. That link is inside the box where your 1-9 heat control indicator is located. There's a little door on the passenger's seat side. Open that door & you'll see what I'm talking about. When mine was broken, I could hear the servo motor operate, but it's arm was unattached due to the broken link. If the link's kaput, the flapper boxes won't receive the signal to open. IIR, I took the passenger seat out to repair it for more room although you can struggle with it if you elect to leave the seat in.

Replacement is nicely covered in the Bentley manual section 801-2 & -3

Gerry

[Luccia at Pelican Parts]

Bentley Manual here for those who need it: Porsche 911 (1974-1989) - Repair Manuals

Also, we do have a tech article that covers the heater system. Maybe it'll be useful to you or others that are running into some heater issues. Can view it here: Porsche 911 Heater System Repair|Pelican Parts DIY Maintenance Article. Good luck!

[polizei]

Thanks everyone! I'll take a look today and report back.

[polizei]

Originally Posted by wrxnofx

If the blower motor in the engine compartment is actually working and you're getting virtually no air in the cabin I'd suspect the flappers, too. Since you mentioned position 9, you must have autoheat. Therefore, it's possible that the servo motor in autoheat box doesn't work or the arm connecting the servo motor to the linkage fell off.

As Gerry suggested, lay under the back of the car so you can see one of the flappers. Then have a friend turn on the key and turn the autoheat knob to 9. You should see the flapper valve rotate the open holes closed (which is also opening the corresponding valve plate inside the flapper housing, allowing air to flow fully into the cabin).

Regardless of whether the footwells are seized or not (which you can easily check by removing the kick panels), there should be a decent amount of air flowing into the cabin at position 9 on the autoheat dial.

OK, so I just watched the flappers as the heat was turned on via the dial between the driver & passenger seats. It closes the holes about 75% on both the driver & passenger sides. It closes at a painfully slow rate. Any suggestions on how to fix this? I'm wondering if I could just try removing any slack of the pull cable at the flapper.

Thanks!

[86 911 Targa]

[QUOTE=polizei;9320186]OK, so I just watched the flappers as the heat was turned on via the dial between the driver & passenger seats. It closes the holes about 75% on both the driver & passenger sides. It closes at a painfully slow rate. Any suggestions on how to fix this? I'm wondering if I could just try removing any slack of the pull cable at the flapper.

Thanks![/QUOTE

Prior to any "intrusive" actions, use WD40, and, lots of it while exercising the flappers.

You should be ok from here forward.

Best,

Gerry

[911obgyn]

Check the hoses from the flapper box to the front of the car, and check the rear of the heat exchangers behind the bumper for open areas. The engine fan and the blower in the engine compartment move air through the heat exchangers on the exhaust to the front of the car. The servo does take a few seconds to move the flappers.

[polizei]

Originally Posted by 911obgyn

Check the hoses from the flapper box to the front of the car, and check the rear of the heat exchangers behind the bumper for open areas. The engine fan and the blower in the engine compartment move air through the heat exchangers on the exhaust to the front of the car. The servo does take a few seconds to move the flappers.

Good call! I found a massive hole by where the passenger side high temp air duct was resting against the exhaust manifold. When I turned the key & heating system on, I felt quite the breeze coming out of the hole

I had 3" ducting. I'm going to replace it with 2.5" and wrap the manifold and muffler with exhaust wrap. Hopefully that will be the trick.

Thanks!