I have just replaced the heater blower and control panel on my 914 and the front trunk blower now works for the first time The previous owner to me covered over the dash vents with vinyl, so I have uncovered and trimmed around these too.

I have totally stripped out the interior, sorted any rust (er... none ) dynamatted the whole interior, put in extra soundproofing, fibreglassed over and repaired the back pad where the board/wood had perished and fitted a new grey loop carpet set from Appearance and Performance, phew. Looks fabulous and returning to perfect condition

Now as I understand it, the dashboard levers work like this...

1. Top lever

FRESH air vent and fan control

2. Middle Lever

Controls direction of FRESH air delivered by above lever (left footwell, right dashboard.)

3. Bottom Lever

Controls direction of HEAT from 4 below. (Again far left footwell, Right Dash vents)

4. Lever between seats

Controls rear fan and therefore HEAT into cabin.

So the front fan plays no part in heating the car whatsoever, just FRESH air.

HEAT is controlled directly by the lever between the seats (the direction of which is controlled by the 3rd land lowest lever on the control panel)

So, if I am correct with the above can you tell me why hot air only comes from the drivers side? It is really hot air on this side and blown with quite a force, yet the passenger side is cool.. I know there are differences between 73 and 74 cars in that the earlier cars (like mine) have a rear fan that only blows down the drivers side and later cars had a T piece which splits the air from the blower and connects to the passenger side, but is this why it is cold on the ps?? Surely it wasn't that bad from the factory in '73??

Long post sorry, but hopefully concise regarding my problem.. My wife is an Aussie and is complaining that she gets cold, so I'm determined to get more heat on her side if possible.

Cheers

You understand the system correctly. Note that there is air blown through the heat exchangers with our with the electric fan on. There is some air drawn from the engine cooling fan to do this. In addition to adding a "Y" and hose to the right side of the car as the newer cars have; you may check to make sure that your flapper valves on the heat exchangers are connected and are working correctly. This is the flapper valve that is located under the car- between the heat exchanger and the passenger compartment. Should be on on each side of the car. Each one has a hose that passes air into the hose that connects to the inner part of the rocker. There should also be a cable going to each flapper valve. These cables are connected to the center lever you described.

Often, these flapper valves malfunction, or are not connected at all. Also, the heat exchanger may have rusted. If so, it will allow most of the heating air to exit before it can go to the passenger compartment. If so, get a good pair of stainless steel heat exchangers to fix this.

JoeO

Awesome a very constructive answer thanks

There is air being blown through the under dash vent so that makes me think that the pipework is intact. But surely ALL of the air coming from the back through the sills should be warm as it goes through the heat exchangers first?

Therefore if there is a flow of air at dash end this means that all is working? or can cold air be forced down the sill pipes if the flapper valves have malfunctioned?

You're pretty much correct and dash controls you've got down pat. But here's a some clarification and info.

Edit: And I realize now that I'm really only expounding on what Joe already wrote, but I typed all of this already before I read Joe's reply so here ya go!

The electric blower motor is very weak and only does any real good at idle or below 2 or 2.5k rpm anyway. Mine doesn't work and I don't even care. I wouldn't bother putting the extra hose over to the passenger side. Just drive faster...

Why?

The floor lever once opened even a little bit, starts to open the heater flapper valves. You don't need the electric motor at all to get heat blowing. But as I said before, it does help below a certain engine rpm.

Why?

Once you reach 2.5k rpm+, the engine cooling fan blows so much air through the HE's and flapper valves that it overcomes anything the electric blower motor can provide (as I said, it's very weak anyway). You've probably already noticed that there is much more air when you're operating the car with the motor at higher rpm's.

Also...

You have to open the floor lever all the way to engage the switch to turn on the electric blower motor BTW. At partial opening, the electric blower isn't turned on, but doesn't necessarily need to be.

If you have no warm air on the passenger side, it's because the flow of warm air from the HE's is either obstructed, or your ducting is not completely installed or rusted away and full of holes. Or the flapper valve is not opening, stuck, rusted away and full of holes. Or your HE's are blocked, or rusted and full of holes. Or any of the heater hoses coming from the rear of the car that carry warm air are missing, blocked or full of holes.

You're probably getting the idea. Good luck!

How about if the flapper valve is completely missing

just had a look underneath and the passenger side Heat exchanger has nothing attached to it and the pipe going down the sill is capped off

Whoever had this car before me never drove it in the winter thats for sure!! So what do I need to find to re-instate it??

Flapper valve
Cable
Pipe?

Hi,
First to answer your question.
You will need the flapper valve and the pipe that connects that to the heat exchanger. You also will need the j-tube pipe that connects to the other port of the heat exchanger and comes up through the engine tin on the passeger side for the heater blower motor.

The cable that goes to the lever on the floor is one long cable bent in half...so get under there and look harder, it may still be there just sticking up in front of the engine doing nothing.

I live in a very cold climate and I found a few simple things to make the head super hot.
You re right that the top lever controls the fresh air fan and vents.
Leave that to the left.
The next one down, the middle lever controls the mixture of both hot and cold air...so leave that to the left.
The bottom one controls the vents for the heat...
Move that to direct heat.

I took off the hose that connects the fresh air box to the mixer valves on both sides of the car (under the dashboard, in the front trunk)
I took spray can covers and screw clamps and covered these ports, both on the mixer valve and the fresh air box.

This stopped all fresh air from entering the car and the front trunk.
I found the mixer valve seals were not very good and in 20 degrees or lower the cold air was winning the battle.

Now, my car is super hot and I need to open the windows in the winter...I can drive at any temp and be vert toasty warm.

Rich