Heater dosent work

[lukecp]

I went to turn on the de-frost the other day, and with the heater turned all the way up, it wasn't even blowing lukewarm air. No difference between it and the normal tempertaure air.

Last spring i put in a new heater core and a new blower motor, but neither made the heater work as good as it should. I still got cold in the truck all the time. I think this is because the heater core is supposed to be insulated against the heater box by something, and mine isn't.

Anyway, my coolant level is full, so why am i not getting any heat at all? Could one of the baffles in the heater box be messed up?

I have been toying with the idea of getting an aftermarket heater and ditching the stock heater all together since it never has worked very good, even with the new blower motor and heater core.

[cdowns]

it's very common for the diverter flap to fail on these trucks . it's the squareish box inside the cab by the passengers feet, you usually end up buying a new box

[lukecp]

I'll take a look at it. Do i have to pull out the box to look?

If i have to get a new box....i think i will just go with an aftermarket heater and ditch the stock heater. It will be nice to clean up the firewall.....

[allgmcs]

It is probably the flapper. It makes a difference where it is if the truck has fact air or not, but you can fix it either way. After a new heater core and functioning flapper (diverter), the heater will run you out of the cab when it is below freezing.

[71-longbed]

now you have heater problems ...wierd

[lukecp]

lol...it is werid. How is yours coming along?

[71-longbed]

i need to call around for heater motors ..then this weekend i'll get her done with the help of my brother ....

i have 1 question ... when i remove the hood hinge to get to the motor ... do i have to remove the spring first .... i think it would make things easier ... but i've never messed with my hinges ... any suggestions from you pro's ??

[COBALT]

...or you could have the problem I had. I rebuilt my heater box on the firewall when I replaced my heater core (complete with new weather stripping, sealant, etc.). I forgot to connect the cable to the little metal door inside the box when I re-installed the box. After warming the truck up I wasn't getting hardly any air. Until I moved the heater control back and forth and realized I had a little too much slack I realized the cable was detached. Once I had it reconnected it worked great!

[lukecp]

I just yanked out the hinge w/o removing the spring. Before yanking the hinge, make sure you can't wiggle out the blower motor. I couldn't on mine....i think it would be worth the try. Also...lay a towel down on your cowl panel. Then if you acceditly let the hood get away, it won't mess up your pretty ochre paint

[lukecp]

Cobalt, where did you get the wheaterstriping? Was it the insulation that goes around the heater core itself?

I was looking at aftermarket heaters......$190 for a nice one...i will just try to fix the stocker, lol. I may just make a trip to the junkyard....the heaterbox under the hood is pretty torn up anyway.

[COBALT]

I got a kit from LMC. It actually worked out pretty well.

[lukecp]

Ok....thanks for the help.

I may go home next weekend so i can tear into this and fix it before it gets cold. I don't want to work on my truck while it is parked along the side of the street, lol.

[GMC Jim]

I repaired both the temperature door and the defroster/floor outlet door. Used a 2-part expoxy mix with fiberglass cloth on both sides of the doors as they were almost broken away from the hinge pivot....This stiffened the doors as good as new or maybe better...Also adjusted and reglued the rubber seal around the edge of the doors.... Re-assembled and everything works fine....and be sure to lubricate the control cables while you have things all apart!...
If you have to replace the blower motor; get the one used with airconditioing as compared to the standard blower.....The standard blowere used with heater only draws 6.25 amps and RPM of 2550 to 2950. The blower used with air conditioning draws 16.5 amps and RPM of 3700 min. The diferent blower motors are interchangeable and a considerable difference in output using the blowere designed got air condition units.

[GMC Jim]

sorry for the spelling in above message....meant that there is a considerable difference in oputput between the two blowers available... I used a graphite speedometer cable lube for the control cables.........Jim

[lukecp]

Well i found the problem today. The heater control cable had fallen off the baffle, and wasn't opening the baffle that lets the heater in. I hooked it back up at the heat works!

Also, when i put in a new heater core this spring, i didn't seal the heater core up against the heater box and firewall with anything. Could that be allowing cold air to blow past the heater core, and if it does need to be sealed, what can i seal it with?

Thanks for the help!

[71-longbed]

i put in the new blower motor today and still nothing ... so i guess i should check the heater resistor ...... anyone ever done one of these .... any tips or trick .... is there an easy wasy to remove the glove box lining ???

thanks

[lukecp]

One other thing to check....make sure your ground is good to the blower motor.

[71-longbed]

clean that grounf up really good ..still nothing ..... im hope its that resistor ....

[lukecp]

Well if it is grounded and has 12v it should work....try jumping the new fan motor from the + battery terminal to and see if it starts blowing.....possible you might have gotten a bad motor.