No Heat? Was there a mouse in the house?

[Larrybrook]

Hey guys I was hoping to get some advice from y'all on why I don't get good heat and what to do about it.

Brief history: I bought my 74 Targa in pieces, and it took several years by the time I re-built everything and put it all back together. I'm 96.3% sure I put all the heater hoses/ductwork back the right way (although I never found the water pump or radiator??? HA!)

Current Status: She's finished now but when I close? the heater vents (beside drivers seat) and switch the fan to high; I only get very cool air with the occasional piece of fluff blowing out...but the cavity around my feet feels nice and toasty.

What to do? Where is the blockage most likely located? I haven't seen any evidence of mice since I got the car so I can only assume it was before I got her.

Of course…there’s a 3.7% chance I put the hoses/ductwork on wrong…

[javadog]

Couple clarifications needed.

By "Close the heater vents beside drivers seat" do you mean you are pulling up on the two red-tipped levers between the seats?

When you switch the fan to high, what control do you mean?

JR

[ossiblue]

javadog has you on the right track.

The two levers between the seats opens the heat ducts when you pull them up. I believe the 74 also has a fan in the engine compartment attached to the heater hoses that will boost the hot air into the cabin--check to see if ducting is attached and the fan is working.
The fan switch you turned on is, I believe, the lever on the dash. That only operates the fresh air blower in the trunk--cold air (top lever on the dash panel). If your feet are toasty, it sounds like the heater is working. If you want to direct the warm air to the windshield, use the red dash lever and slide it to the upward pointing arrow.

[Larrybrook]

Couple clarifications needed.

By "Close the heater vents beside drivers seat" do you mean you are pulling up on the two red-tipped levers between the seats?

When you switch the fan to high, what control do you mean?

JR

Yes, Pull up on red tipped levers, thus allowing warm air into duct work, and the fan is indeed on the dash wich is supposed to pull all that warm air up to where it's need the most...right?

I recon I'm just going to pull the hoses/pipes/tubes off in the spring and get busy with the shop vac.

Make sense??

[dan79brooklyn]

I would check the cables and the heater box that connect to the heat exchangers, you can reach under there and feel that the flaps are closing and opening when you pull up/push down on the lever near the e-brake.

[javadog]

Originally Posted by Larrybrook

Yes, Pull up on red tipped levers, thus allowing warm air into duct work, and the fan is indeed on the dash wich is supposed to pull all that warm air up to where it's need the most...right?

In a '74 911, there are no fans to boost the heated air output. This started with the '75 models. The red-tipped levers open valves under the car that admit heated air into the cabin. This air is diverted from the engine cooling air and so the quantity of heated air sent to the cabin is directly proportional to engine revs.

The lower red-tipped lever on the dash controls where the air is sent. When positioned to the left, it sends the air to the footwell vents. When positioned to the right, it sends it to the windshield vents. Any position in between splits the air proportionally to both.

The fan that you are activating by using the top lever on the dash controls the fresh air only, which is unheated air drawn from the outside through the grill at the top of the trunk lid. The middle lever controls where this air is sent, in the same manner as the lower lever controls the distribution of heated air.


JR

[tcar]

Originally Posted by Larrybrook

Couple clarifications needed.

By "Close the heater vents beside drivers seat" do you mean you are pulling up on the two red-tipped levers between the seats?

When you switch the fan to high, what control do you mean?

JR

Yes, Pull up on red tipped levers, thus allowing warm air into duct work, and the fan is indeed on the dash wich is supposed to pull all that warm air up to where it's need the most...right?

I recon I'm just going to pull the hoses/pipes/tubes off in the spring and get busy with the shop vac.

Make sense??

No. It's a complicated system.

Re-read the above.

When you pull up the red levers you are OPENING the heater vents, not closing them as you said.
There is a FAN in the rear, also that's supposed to go on when the red levers are pulled up. Yours sounds like it's not working. It's on the upper left (driver's) side of the engine, toward the front of the car by the firewall.

The fan that you are talking about has NOTHING to do with the heater. All it does is pull in COLD air from the vent on the front hood. Nothing else.

[Craig]

Javadog and ossiblue are right on in their description of how the heater system works. From your description that you get heat down by your feet, I think the heater hoses and heat exchanger connections are working fine, and the red levers between the seats also are working.
You just have to remember that if you turn on the fan in the dash, you also have to adjust the other 2 controls in the dash for heat/direction also.
Just keep playing with the controls in the dash, and you will eventually get it figured out.

I have had mine for 10 years, and still have to mess with them to figure it out every time I use them.
Craig

[javadog]

Originally Posted by tcar

When you pull up the red levers you are OPENING the heater vents, not closing them as you said.
There is a FAN in the rear, also that's supposed to go on when the red levers are pulled up. Yours sounds like it's not working. It's on the upper left (driver's) side of the engine, toward the front of the car by the firewall.

Actually, he was stating it correctly. The heater valves are normally open, discharging the air back under the car. When heating is called for, the valves are closed and heated air heads to the cabin. Semantics, maybe.

And the '74 he has never had the engine fan. That began in 1975.

JR

[tcar]

Originally Posted by javadog

Actually, he was stating it correctly. The heater valves are normally open, discharging the air back under the car. When heating is called for, the valves are closed and heated air heads to the cabin. Semantics, maybe.

And the '74 he has never had the engine fan. That began in 1975.

JR

Thanks. I just assumed that it changed with the bumpers. I knew my '73.5 didn't have one. Silly.

[Larrybrook]

Wow...I guess I haven't been operating the dashboard levers properly. I'll figure it out in the spring. Deffinitly no fan in the engine compartment/firewall, I know the heater valves are working perfectly, I replaced them and lubes up everything down there...AND like I said, there's plenty of heat around my feat, just cold air on the windsheild and the occasional piece of fluff, which made me think of mice.

No worries gentlemen, I appreciate your imput.

This is my first Porsche, I had NO IDEA they were this complicated/foreign. But what a wonderfull way to learn, re-assembling what someone else took apart!!

Cheers!

[tcar]

These cars have 3 separate systems (if they have A/C) that are not integrated.
1. Heater operated on the floor (except for the red lever to direct heat to floor or w-shield)
has a fan in the rear on '75 and later cars.

'74 and earlier cars use the engine cooling fan to act as a heater blower.

2. Fresh Air - operated on the dash with another fan in the 'trunk' in the front.

3. A/C - if you have it, controlled on the console, or on the kneepads, with another fan in the
smuggler's box.

If you are running the fresh air fan with the heater, you are defeating the heater. Move the upper lever(s) on the dash all the way to the left.

[doug_porsche]

So thats how the heater controls work!

I figured it was easier to put headers on the car. That way I was never tempted to try to figure it out.