Heating the cab pickle! Help please

[nateshrek]

I have a 65 gmc, and I just replaced the heater core under the hood. The blower motor was replaced at some point (not by me) and seems to work fine, all three speeds. All the under dash hoses are connected with no clogs. After reading maybe people saying their new heaters were roasting them out, I figured mine would do the same. But after flipping the switch, it's more like a light to medium fart, not hurricane gussy. But seriously it barely blows enough to feel with your hand over the vents.
Any ideas as to what I can do to get more airflow into the cab?
One thing I may add, when I installed the blower motor with cage onto the unit that bolts to the firewall, the hole that is in the box, right overtop the top of the cage, was scrapping. Is that tolerance between the bottom of the box and the cage to close not pulling enough air?
Please anyone with ideas, let me know

Thanks guys.

[pimpston65]

Originally Posted by nateshrek

I have a 65 gmc, and I just replaced the heater core under the hood. The blower motor was replaced at some point (not by me) and seems to work fine, all three speeds. All the under dash hoses are connected with no clogs. After reading maybe people saying their new heaters were roasting them out, I figured mine would do the same. But after flipping the switch, it's more like a light to medium fart, not hurricane gussy. But seriously it barely blows enough to feel with your hand over the vents.
Any ideas as to what I can do to get more airflow into the cab?
One thing I may add, when I installed the blower motor with cage onto the unit that bolts to the firewall, the hole that is in the box, right overtop the top of the cage, was scrapping. Is that tolerance between the bottom of the box and the cage to close not pulling enough air?
Please anyone with ideas, let me know

Thanks guys.

ive heard of folks putting the cage on backwards, did you install that blower as a unit? or did u put the cage on then installed it? i ask for your sequence of events in order to see if there was a chance the cage go put on backwards...

[nateshrek]

Doesn't the cage only go on one way? Since it's kind of "dished" so the bottom of the cage reaches the bottom of the motor housing?

[pimpston65]

Originally Posted by nateshrek

Doesn't the cage only go on one way? Since it's kind of "dished" so the bottom of the cage reaches the bottom of the motor housing?

there was a post awhile back where a member was able to put it on incorrect. can you post a pic of it? without tearing too much apart of course...

[pimpston65]

does it look like this? which is incorrect

[pimpston65]

it should look like this!!!

[nateshrek]

Thanks for the picture bud, I'll have to check it out tomorrow when I have some daylight. You don't happen to have a picture of a correctly installed one do you?

[nateshrek]

Lol sorry I didn't see the second picture. I'll look tomorrow

[ACK]

From what you're describing, you have the thrift air heater. If Pimpton65's diagnosis isn't the issue, here's some additional thoughts:

If you're barely feeling a breeze coming out the defrost or bottom heating vents, good chance there's a rodent or mud wasp nest in the heater box. Disconnect the heater control cable and unbolt the heater box inside the cab and see if there's any blockage.

If air is blasting out, but it's not hot, some culprits include:
- Air pocket in the heater core
- The hoses on the heater core are swapped
- Thermostat stuck open

Good luck and let us know the outcome.

[jtrichard]

show us a pic of how the hoses are run

[nateshrek]

Originally Posted by jtrichard

show us a pic of how the hoses are run

Doesn't the 5/8 from the thermostat go to the 5/8 on the core? Then the 3/4 from the water pump to the 3/4 on the core?

[BR3W CITY]

Just for comparison, I have a heater system that is at minimum 20 years old, and at most, original to the truck.

I'm not sure "which" heater I have, but I don't have a/c, just the regular "pull for heat" and rotate the thing for how high. On high, it blows like a "3" from a more late model vehicle. It does however make plenty of heat. I've never had it out in less than ~45*, but it made enough to warm the cap thoroughly and defront sorta. Its more than I'd expect from a 50 year old truck.

[nateshrek]

Well,i couldn't sleep last night and at 11 pm busted out the work lights. The cage was on the motor wrong,so I fixed that And it helped but still not what i was thinking. Maybe I'm expecting to much. As fa. As stuff in the box, i just disassembled the whole thing and paint it. The only part that has not been touch is the part from the firewall to the vent tubes inside the cab. But the truck has not been sitting. Maybe that will be the next step...
Thanks for the replys back guys. Keep'em commin?

[aerotruk63]

Have you tried going over the cab body and blocking any holes that you can see from inside? Are your door weatherstrips in good shape?
These old trucks are steel against cold, no insulation. Body panels are sucking the heat out.. Just think of the cab body as a core, and you little heater core is trying to compensate.
What temperature is the truck operating at?
One thing I installed on my 62 K10 was a Bus Style inline block heater. If your doing short distances, the truck will not get to optimum heating temp.

[ACK]

Just checking to see if you've narrowed down the issue. Have you warmed up the engine and checked the hose going into the core to confirm it's hot? If it's not, the issue is in another area.

Aerotruk63 is right. I replaced my heater core this past fall. I'm running a 4.1L with thrift air, door and cab seals are in good shape, no carpeting or sound deadening material. On a cold PA day, it takes about 10 minutes for truly warm air to start flowing, it takes a good 10 miles of driving before it gets real toasty in the cab. I typically run the heater on medium speed unless I'm at a long stop light, then I will crank it to high and take advantage of the extra radiator heat build up.

[Greg63]

Is the blower motor correct? You say it was replaced before you got the truck - maybe the motor spins in the opposite direction?
Greg.

[nateshrek]

Hey just an update. The heater is working better now, keeping the fluid levels up. Now all I have to to is seal the cracks and hole. Thanks for all your help gentlemen.