Duster Heat?????

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gunbunny

gunbunny

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I've read some other posts, not really finding a good answer to my issue, so here goes.
74 Duster /6 no air.
I'll just write it the way I expect my techs to with the 3/C's
Complaint: Wife says heat doesn't work!
Tech Notes: Checked coolant, OK. Replaced older weak radiator cap as precaution. Checked heater hoses, both are warm to touch, Checked blower motor, works at all speeds. All hoses and ducts are present and in working order. Checked function of heater box doors and cables, all seem to be free and working properly.
Function Test: Started car, allowed to heat up.
***NOTE**** Turned on heat, hot air blew thru duct immediately followed by cold air.
Cold air is over powering the warm air that system is trying to produce.
Cause: Further inspection of the heater box has revealed that, there is a significant draw of cold air from the right side fresh air duct when the blower motor is in use.
Cure: ????

Ok, this is where you come in! My initial inclination is to block the fresh air duct. But that's not right. I was also wondering about the seals on the heater temp door, but then, I get to wondering if the blower motor needs the air in order to circulate. The seals didn't seem bad, but I also didn't give them a love affair look either. I was on my knees in the cold.
The short term solution is to block the fresh air duct. The fan can pull enough air from the passenger cabin to keep from burning up, and the air temp will rise, in theory.
Ideally I just rather the wife not drive the car, but we have 2 down. She managed to blow the brake lines on truck the other day, and she blew the Jeep up this fall. I got the 3.7on a stand trying to put it back together between paying work, and she brings the truck in to me. So besides not letting my wife drive at all any thoughts, suggestions?
 
on the passenger inner fender, is there a vacuum operated valve that opens and closes? one of the heater hoses runs to it, then from it to the fire wall, is this working properly? I put a small ball valve in place of it on my son's duster, cured the issue, open for heat, closed for air.
 
It's supposed to pull its air from right cowl opening.
There isn't a hot water cut off valve where there isn't a/c .
To flush the heater core..Take the heater hoses of engine end and drape them over the right fender. Use a garden hose to flush the heater core in both flow directions until the water runs clear.
 
I would just buy a new heater core. Easy to change and they're $35, IIRC. It's about a 2 hour job taking your time.
 
I had a slant one time that did not make very good heat
Come spring time it started running hot.
Turns out most of the water pump impellers were about corroded off.
 
If both hoses are good and hot, it's not a plugged heater core. "Just feeling," check the top main radiator hose and then feel the heater hose next to it. you should not feel much difference

You may feel some difference between the two hoses at the heater, but not a lot. In any case the cooler one should be 'good and warm.'

Is the engine running up to temp? Do not go by the gauge.

If both hoses are luke warm you may have a water pump impeller broke (rusted) loose off the shaft.
 
67Dart273 said:
If both hoses are good and hot, it's not a plugged heater core. "Just feeling," check the top main radiator hose and then feel the heater hose next to it. you should not feel much difference

You may feel some difference between the two hoses at the heater, but not a lot. In any case the cooler one should be 'good and warm.'

Is the engine running up to temp? Do not go by the gauge.

If both hoses are luke warm you may have a water pump impeller broke (rusted) loose off the shaft.
Click to expand...

There can be a small amount of water flow and the heat will migrate in both hoses even with no water flow. Go feel the cold water supply line of most water heaters while standing idle for proof.
He said he gets hot air initially ( migrating heat ) followed by cold air so air flow isn't the problem. He didn't say engine runs hot so water pump isn't the problem.
I don't mind being wrong. It happens. lets let the thread starter prove me wrong.
Cheers
 
Yep, partially (mostly) plugged heater core.
Both hoses luke warm can just be because of restricted flow.
 
While my current Dart is strictly a warm weather vehicle (no way am I gonna let salt get to it!), my recollection of the '70 Dart I had back in the day was the heaters in those cars were never any great shakes to begin with. In temps much below 15-20° out, it was pretty feeble, even when new. I did find that if I ran it in defrost it seemed to heat a bit better, I also put in a 205° thermostat which helped some too.

Your idea of blocking off the fresh air intake and if you left the passenger's side vent door open you'd have enough airflow, and just recirculate inside air. Never thought of that back then. Wouldn't hurt to try.

I suppose it could be a heater core, but every one I've ever had to replace was because it leaked, not plugged. I suppose you could try flushing it. I know, loads of fun in below-freezing weather.

For some reason, a lot of those old Mopars had wimpy heaters...I had a Horizon in the 80s that was as bad if not worse. On that one I added a 2nd heater core over the intake as a pre-heater. Not really practical on an A-body though...
 
RedFish said:
There can be a small amount of water flow and the heat will migrate in both hoses even with no water flow. Go feel the cold water supply line of most water heaters while standing idle for proof.
He said he gets hot air initially ( migrating heat ) followed by cold air so air flow isn't the problem. He didn't say engine runs hot so water pump isn't the problem.
I don't mind being wrong. It happens. lets let the thread starter prove me wrong.
Cheers
Click to expand...

My slant never ran hot, until spring.
The water pump was shot.
A quick check is grab the fan blade and wiggle it side to side.
If it moves at all it's wore out.
The heater core could be plugged or for some crazy reason mice made a neat
In the heater ducts.
 
Describe your climate control buttons. Without factory AC, I suspect yours is just a manual cable control. My 64 & 65 A's are like that. My 65 Newport is non-factory AC, and has a 4-button pnuemo-electric push-button, but I haven't heard those ever came in A-bodies.

If a simple manual cable, check that it works. If you remove the glove-box liner, you have a clear view of the cable and fresh air door pivot. I think the only temperature control is the driver opening the fresh air door more and/or changing blower speed. I prefer that to my 80's M-B with their funky auto temperature control that has a mind of its own (descended from 50's Mopar design I read).
 
RedFish said:
There can be a small amount of water flow and the heat will migrate in both hoses even with no water flow. Go feel the cold water supply line of most water heaters while standing idle for proof.

Cheers
Click to expand...

I should have mentioned to check the hoses with the heater in the "full on" and fan high. If you don't get heat out of the thing and seconds later check the hoses, and they are both hot, you have some sort of airflow problem, like damper doors, etc.

This is "heat exchanger 101"

The reason you don't get much temp drop in a properly operating system across the hoses is simply that there is so much coolant flow.

I can guarantee you that if the heater core is plugged enough to cause "cold" output, the outlet hose will be cold when the blower is on high
 
Do this and you'll get your heat back. Be sure to REVERSE flush it. It took me twice on the '73.

[ame="https://www.youtube.com/watch?v=D0bWaFeX0Go"]1973 Plymouth Valiant heater core flush - YouTube[/ame]
 
Try reverse flushing first. If you have a compressor, turn regulator down to 20psi and reverse blow out. If no success, reverse flush block. If no success, flush radiator. If no success, get a temp gun from Harbor Freight and find out where cold spots are. I don't think it's the WP but there always a chance.
 
Sorry it took so long to get back.
OK, now I had a chance to actually bring the car inside and do something with it.
I changed the thermostat and flushed the system. Pressurized the system just to be sure and that was good. burped the system of air and I'm pretty sure there is circulation.
No heat!
Now what!
So I felt the heater hoses, the input hose is hotter than the hinges of hell! the output, cold as ice.
So I'm guessing I either have a clogged heater core or a bad heater core.
Sooooooo
It was to hot to go back and try to flush again, Monday is another day and I'll put some pressure on it then.
 
That was my first thought when you posted, but in the OP you said both hoses were warm.
 
gunbunny said:
Well, in -11F cold, 30F water feels pretty dang warm! :eek:ops:
But inside, not so much.#-o
Click to expand...


lol

I would try and reverse flush it like mentioned above with both hoses disconnected so you're concentrating on just the heater core, that couple with some bursts of compressed air, might clean er out.
 
Reverse flush it and have an extra length of hose to catch what comes out in a bucket for a visual. After you reverse flush it run the flush the other way. If you have good flow through the heater core with a water hose hooked up to it, it's not blocked.

If you still don't have heat after reconnecting everything and the return hose is still cold then look at the water pump or for a blockage up front. Run water through the hose to check that the hose itself isn't collapsed inside or the nipple plugged with corrosion. I think after doing a core flush, I'd replace all the hoses anyway and check the nipples. If everything is clear, move onto the water pump as others have suggested. There's not much to the system, you just have to start at one end and work through it. The only thing that you can't really see or inspect with hose flow is the water pump impeller.

One thing you didn't mention, is this vehicle new to your family? Did it have heat before that you know of?

The one thing I was wondering about when you say you get a burst of heat and then cold makes me wonder if there's a loose blockage like a big flap of RTV that's gotten loose in the cooling system and gets pushed up against an inlet of something.
 
Like I mentioned above, it took two tries before the heat would remain working. You can see the goop that came out on the first pass.

The second time I rigged this arrangement so I could run water through it for an extended time without having to stand there and hold it.

Pay careful attention to the output and input of the heater core. Inflow is normally the hose closest to the center of the car, so push water the opposite direction to reverse flush it.


[ame="https://www.youtube.com/watch?v=kPSlcrqXCC8"]Redneck heater core flushing device - YouTube[/ame]
 
Well, I've had the car not quite 2years now. But never drove it in the cold weather until this year. So, that is new to me.
The car had to become a daily driver, but thankfully just for short trips.
I'll flush the heater core at the shop again. We have a power flush system at work, I know nothing about it, but I'm going to ask and get an education.
At the very least, it will reclaim my 2gal of new coolant.
 
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