Heater question -- penguin sighting

[green71]

Boise in February is a time when a young man’s thoughts naturally turn to THE HEATING SYSTEM IN HIS CAR. How on earth does this thing work? Or more appropriately, how is it SUPPOSED to work?

I can get heat by pulling up the red-handled lever between the seats, but it’s kind of an ambient heat that doesn’t seem to come from a particular source. And although the heater blower motor seems to be ducted to the warm air guides/heat exchangers, turning the blower motor on via the dash lever produces no heat at all. It just blows cold air into the car. Defrosting the windshield is particularly a drag.

Does this sound like it’s to spec? Or is my system screwy?

Thanks,

Mark

[Pritchard]

It sounds like your system is working the way it is supposed to. The top two controls on the dash are for unheated air only. Thus the cold air when you slide the upper arm to the right. The red lever near the gearshift turns on the heater blower in the engine bay and opens the butterfly valves on the heat exchangers to allow heat into the cabin.

To get the most heat out of your swystem, ALL pieces of the heater ducting must be in place. Even the gasket pieces under the fan shroud. Why? Because the engine fan is what moves most of the air that you will receive heat from. The lever-controlled blower in the engine bay only acts as a booster when the car is at idle.

Check to make sure that you have everything mostly leak proof (for the air being blown into the HE from the engine cooling fan) under the car. This is where most of your heat will come from.

Or do like I do, wear more clothes!

Good Luck

Pritchard

[Dave at Pelican Parts]

Check the FAQ, it answers the "how does the heater work" questions.

In short, the lever between the seats turns on the heater blower only when it's pulled up all the way. The lower slider on the dash directs warm air up or down.

--DD

[green71]

I’ve read the FAQ’s and it seems that my system functions as the FAQ describes.

Are there two blower motors? One for heat, one for fresh air? Was the heater blower an option that my car or model year (1971) might not have? I don’t hear a motor come on when I pull up on the floor lever. Where would this blower be located?

Thanks,

Mark
1.7l Frigidaire

[RichMason]

The heater motor is in the engine compartment. You can hear it when the engine isn't running but the key is turned on (and the lever is pulled up). If it doesn't come on check your fuses and relays. A I understand it, these motors can also just freeze up from disuse but this can often be overcome by sticking your fingers (with everything turned off!) into the motor and turning the fan to get the bearings moving again. As pritchard pointed out, the system has to be in great shape to really generate heat and it will always work best when you are taching 4K or more. Good luck!

[Dave at Pelican Parts]

Yup. And the fresh air blower is up under the cowl in front. Two blowers.

70-72 cars had a heater blower up on top of the fan shroud, pretty much in the middle of the engine bay. It had two outlets, one going to each side.

73-74 had a heater blower on the left side of the engine bay, mounted on the car's body. It had one outlet only, which went to the left-side heat exchanger only. The "J-tube" on the right side was capped off.

75-76 had the same location and blower as thhe 73-74, but there was a splitter on the outlet and one hose ran to each of the two heat exchangers.

--DD

[prattrc]

When my heat is on full blast and coming through the windshield vents, I can definitely tell where it's coming from. When I have it towards my feet, it's a kind of that ambient feeling, like you said.

Either way, I can't have it on for longer than a few minutes at full blast, or I start melting. It does take a few minutes to warm up, but after it gets hot, it's nice 'n toasty.

I drove my 72 with headers from Atlanta to Nashville in January one year. It was below zero in the mountains. I had to alternate sitting on one hand and steering with the other. I forgot my gloves. Ambient heat? It could be worse, I s'pose.

[green71]

Right on. All the hardware's there; my guess is I need to chase down an electrical fault.

Thanks for the help!

Mark

[John Rogers]

Look through the tech articles for the one that shows how to add the two extra three speed fans in the front trunk. Seems like a lot of the air gets lost somewhere between the heater boxes and the front valve system and this is with new flex hoses, flappers, etc. I added the fans to our stock 914 and in a half mile the hot air will blast you out! Good luck.

[scotty914]

see my post free heat upgrade

it does the same thing as the fan upgrade ( the one the fans up front ) , but uses the fresh air blower instead of a 120 dollar kit and no need to use tons of tape and jury rig it with tape

[Arlen]

Funny thing with my heating system (up here in Pullman WA at WSU, it gets freakin COLD) is that every so often I get this light headed feeling. Whenever someone else rides in it, the tell me they feel sick, "What is that EXHAUST smell?".

I've grown used to it, but usually leave my heat OFF, alternate hands while driving, wipe the windshield with a rag every few seconds... ahh, spring, so far away...

But what really set my nerves was when I saw a thick cloud of exhaust billowing out of the two front vent above the dash!

The heating system is wrapped around the exhaust system in this air cooled engine, no? Maybe a hole somewhere along they way, which is leaking exhaust into the heating tubes?

[HMeeder]

Ooooh, carbon monoxide, not good.

Arlen; does the ride home kind of get a floaty, cloud-nine feeling? You really need to find that exhaust leak before the medics find you with your eyes rolled up into the back of your head and a big fat drool spot on your shirt.

Seriously, the heat exchanger may be rusted and banged up and not worth a damn for heating the car, but it should never be venting exhaust fumes directly into the car. You quite likely have a leak at the head/heat exchanger junction. I would replace the copper exhaust gaskets. They crush down and form a good seal when carefully and evenly torqued down.

[Arlen]

Ya really, not good! I got the floaty head feeling back before I quit using heat. With the snow on the ground I'm not doing anything except finishing my sound system. When the sun comes back out and I can touch the chasis without getting freezer burn I'll find the source of the problem.

[RustyWa]

I just figured out my heating system and it works very well, even though my heat exchangers have holes in the rear part of the tin.

I didn't know that you could pull the floor lever "up" and you would just open the flappers. I was always pulling the floor lever "up and back" to it's furthest position which would open the flappers and turn on the fan.

Now it is much more comfortable in the cab. Just right.

[Joe Ricard]

I have been searching old posts and found some interesting stuff. The aux fan in the engine compartment is gang wired from the crazy seat belt interlock buzzer thing. (right?) at least on my 74. Found one fellow that just ingeniously rewired the thing to a switch on the dash. (this is where I want to go).
Dopy me I pulled the relay out and started to do a rewire job. OOps made thing alot worse. now I am into it deep. I am drawing my new wiring diagram and will post it if it all works.
HAS ANYONE BEAT ME TO IT N o need to re-invent the wheel here.
summer is about 3 weeks away down here should have it done by then.

[Dave at Pelican Parts]

Usually smoke and stink in the cabin when you turn on the heater is caused by oil that has dripped onto the heat exchangers. (It seems like you can have a leak at the front of the car and it will still find a way to drip on the heat exchangers...)

Actual exhaust leaks are much less common--but are much worse for you, because you often cannot smell or see them. You may be able to use a household CO alarm to see if you're getting carbon monoxide in the cabin. If so, then it is very likely that the exhaust pipes are indeed leaking into the heat exchanger part. As noted, this is Very Very Bad--possibly fatal.


The heater blower fan is run by the rear-most relay on the relay board. The relay is triggered by the lever on the center tunnel--this lever grounds the wire that runs to it, which is what triggers the relay to close. The Infamous Seatbelt Interlock Relay doesn't have anything to do with it, I don't think.

The Relay has only one real function, to keep the starter from working sometimes. Permanently join the two fat yellow wires (one may have a red stripe) together and it should be disarmed. There are other wires going to it, but they don't do anything once the relay is unplugged.

Ugh, that's not quite precise, but I'm having trouble expressing my thoughts. Some of the wires carry power to the relay connector, and another wire is crimped into that connector as well. The second wire carries the power to something else. If you cut off the connector, you have to splice those two wires together to make sure the "something else" still works. I hope that is clear.

--DD

[rdupre@houston.rr.com]

My heater hasn't worked since I got my car. Most probably because the blower was missing.

Last summer, I picked up another blower but it didn't work when installed (it does when you hook up power to the terminals though). Well it was too damned hot in Houston to worry about it then.

This thread is causing me to rethink it and see if I can get the little bugger pumping again.

[green71]

Mission accomplished. There was a spotty connection at the relay, so I cleaned up the contacts & popped a new relay in. I also cleaned the contacts at the lever. Everything seems pretty solid now, and the fan kicks up a good amount of heat.

Thanks for the help,

Mark