Heating Mystery

[jpr2013]

So a little background, I've got a 78 SC that's had a 1986 3.2l swapped in. The engine blower is the big stock unit. The car has footwell blowers and has manual heat (two levers between seats). The under dash wiring appears to be a wild mess, and it wouldn't surprise me if whoever did the conversion introduced some issues into the wiring system.

Basically as soon as I got it, I noticed tons of heat at my feet. Pulling up and pushing down on the levers increased the heat somewhat but didn't really reduce the amount of heat. I read up on the flapper boxes and my first project was getting under the car, lubing and adjusting the flappers. I thought I'd largely fixed them. Then I ran into some issues with my voltage regulator which turned into a new fan housing . . . long story short, the car sat for about 4 weeks while I waited on parts, got the new parts coated, and got everything reinstalled.

Now that the car is running again, it seems like my heat issue has gotten even worse, although that may just be a function of the fact that it's July in Houston. Additionally, I've now noticed that no matter what I do with the levers (between the seats or at the dash), the footwell blower on the driver's side is dumping an enormous amount of very hot air into the footwell all the time. It never turns off. Long-term I'd like to backdate the heat and get rid of the engine blower, but for now I want to be able to drive the car without extra heat being piped in. There are, as far as I can tell, two issues:

1. Clearly whatever I did with the flapper boxes was not enough since heat is still getting in. I know I need to get back under the car and look at these again. I may need to replace the cables and/or the flappers.
2. I don't know why the footwell blowers are blowing at all with the levers down. Whatever the issue with respect to the flapper boxes, the footwell blowers are making things much, much worse.

I'm just about at the point of just pulling the footwell blowers (which make this into an unbearable issue rather than just an uncomfrotable one) or even cutting the hoses to the flappers so no heat can get up front.

So, any thoughts on possible solutions besides what I've laid out above? Alternatively, any suggestions for how to absolutely prevent heat getting up front but in a way that's easy to fix? I don't think I need heat at all in Houston (knock on wood), at least not right now, so I'm inclined to take an easy fix so I can ferret out these issues further down the line.

TIA for any advice.

[86 911 Targa]

The.very first thing I would is to obtain a circuit diagram.

I was not aware that your model/year had footwell blowers.

Pm me as needed.

Best

Gerry

[jpr2013]

Thanks, Gerry, I'll see what I can dig up.

I didn't think the 78 had footwell blowers either, I'm assuming they were added when the conversion was done.

[dyount]

I'm wondering if the engine compartment blower is stuck on possibly? Not sure of the manual cars but with autoheat the blower won't come on until I turn the knob far enough and the sensor says it's good.
Wondering if there's a sensor to your controls? Sensor would run a whiteish wire to the flapper box drivers side

[creaturecat]

unplug at footwell blower.
recheck flappers. adjust/repair accordingly.
heat escaping/entering on one side only?

[jpr2013]

Originally Posted by creaturecat

unplug at footwell blower.
recheck flappers. adjust/repair accordingly.
heat escaping/entering on one side only?

Definitely worse on the driver's side. Passenger's side only gets a bit unless you pull up the red floor lever.

[jpr2013]

Originally Posted by dyount

I'm wondering if the engine compartment blower is stuck on possibly? Not sure of the manual cars but with autoheat the blower won't come on until I turn the knob far enough and the sensor says it's good.
Wondering if there's a sensor to your controls? Sensor would run a whiteish wire to the flapper box drivers side

That could be, as I know the footwell blowers should run while the engine booster fan is on. Any easy way to figure that out (unplug a fuse/relay or something)?

I don't recall a wire run to the DS flapper box, but I'll check it out when I get under the car this weekend. My understanding is that for a manual heat car, the floors level should also actuate a switch that activates the engine blower.

[creaturecat]

undo the wire to the flapper box. lubricate the assembly - make certain it "springs" open.
leave it unhooked for the time being, if need be.

[jpr2013]

Originally Posted by creaturecat

undo the wire to the flapper box. lubricate the assembly - make certain it "springs" open.
leave it unhooked for the time being, if need be.

That's a thought, it'll be months before I need any heat (if ever), so why not unhook it and leave it shut?

[creaturecat]

Originally Posted by jpr2013

That's a thought, it'll be months before I need any heat (if ever), so why not unhook it and leave it shut?

you wanna leave it open.
not shut.

you will still have heat from the pass side, if needed.

[darrin]

why not start by trying to fix the flapper box completely/comprehensively now? -- that way you won't need to do the same job twice (first disable and then REALLY fix when you need the heat to work) -- suspect that if I took the suggested course of action, I'd only remember that the drivers side heat was inoperative when trying to use it to defrost a fogged up windshield during a heavy rainstorm or an early winter blast.

[jpr2013]

Originally Posted by darrin

why not start by trying to fix the flapper box completely/comprehensively now? -- that way you won't need to do the same job twice (first disable and then REALLY fix when you need the heat to work) -- suspect that if I took the suggested course of action, I'd only remember that the drivers side heat was inoperative when trying to use it to defrost a fogged up windshield during a heavy rainstorm or an early winter blast.

I take your point—there’s a lot to be said for just crying once. But there are other projects I’d prefer to spend wrenching time on, and I think after my recent adventure with a voltage regulator issue turning into replacing the fan housing, I’d prefer to just be able to enjoy the car (driving the car in Houston summer is brutal) and put hours in on my other projects (door stop reinforcement, swap decklid for new one with whale tail, replace door cards). I feel like the way this is going it ends with replacing the flapper boxes, the cables, and the ducting, and frankly I’d like to defer it.

Anyway, I think this weekend I’ll take another shot at adjusting the cables and lubing the boxes. If that doesn’t work I may go ahead and try to get the boxes off the studs to see if there are issues I can’t see going on.

[smadsen]

If the flapper doesn't fully "dump" heat, even by a 1/16" mal-adjustment, it can become insufferably hot in the cabin on a warm day. My "control wire" had been bent and trimmed several times. The only fix was to open the heater controls on the cabin tunnel and thread new ones down thru the cable housing. Before adjusting and locking it down, loosen the flapper with some spray lube so it easily seals against the flapper box. The adjustment should leave a little tension on the "control wire" to make sure the flapper stays sealed in the "dump mode." In other words, you have dump 100% of the heat, not 98%.

[jpr2013]

Originally Posted by smadsen

If the flapper doesn't fully "dump" heat, even by a 1/16" mal-adjustment, it can become insufferably hot in the cabin on a warm day. My "control wire" had been bent and trimmed several times. The only fix was to open the heater controls on the cabin tunnel and thread new ones down thru the cable housing. Before adjusting and locking it down, loosen the flapper with some spray lube so it easily seals against the flapper box. The adjustment should leave a little tension on the "control wire" to make sure the flapper stays sealed in the "dump mode." In other words, you have dump 100% of the heat, not 98%.

Now this sounds exactly like what had happened to me, I adjusted the wire, things were better, over time they got bad again. I'm still going to pull the boxes off to do a real thorough cleaning and potentially have them coated (I'm thinking cerakote given how cheaply my local shop will do it), but I'll go ahead and get the cables ordered as well.

[creaturecat]

my solution costs $0. will keep you going. - for the sake of 10 minutes work.
plan on doing some swearing putting the new cables in place. : )

[jpr2013]

Originally Posted by creaturecat

my solution costs $0. will keep you going. - for the sake of 10 minutes work.
plan on doing some swearing putting the new cables in place. : )

Ha! I hear you, creature, thanks again for the advice. Maybe I'll have second thoughts. I'll probably end up going your way!

[Solamar]

Originally Posted by jpr2013

Ha! I hear you, creature, thanks again for the advice. Maybe I'll have second thoughts. I'll probably end up going your way!

If you do decide to pull off the heat control boxes, pre-treat the studs/nuts with a good penetrant. If your car ever lived in a corrosive environment, those little nuts seize to the studs and snap them off from the tub (they are welded to the tub). Don't force them...

[Solamar]

And seeing as how you live in a warm climate, I'd seriously consider backdating your heat - get rid of the engine blower, footwell blowers etc. With just the main engine fan you will get plenty of heat.

[jpr2013]

Originally Posted by creaturecat

my solution costs $0. will keep you going. - for the sake of 10 minutes work.
plan on doing some swearing putting the new cables in place. : )

Originally Posted by Solamar

And seeing as how you live in a warm climate, I'd seriously consider backdating your heat - get rid of the engine blower, footwell blowers etc. With just the main engine fan you will get plenty of heat.

Originally Posted by Solamar

If you do decide to pull off the heat control boxes, pre-treat the studs/nuts with a good penetrant. If your car ever lived in a corrosive environment, those little nuts seize to the studs and snap them off from the tub (they are welded to the tub). Don't force them...

Back-date is definitely the plan. Just been trying to sort through the many, many threads on the topic and figure out how to get the parts I need. One hesitation is that there seem to be some fitment issues with the left side turbo heat duct our host offers, though reviews are mixed on that point.

I’ll be careful with the studs, that’s one thing everyone seems to agree on!

[smadsen]

I see the cables are $10 each from our host. The cable housings are a bit more pricy.

They are a bit of a pain to get to. Much easier with an assistant to push/pull the levers while someone under the car observes the flapper movement/sealing and locking down.

A good "while you're there" is to change out the Delrin parts in the shift mechanism, since the center console has to come off to get at the heater controls.