LT1/LT4 Tech 1993-1997

Weird heater problem very weak heat

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Old Nov 9, 2011 | 09:31 PM
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Default Weird heater problem very weak heat

I could have swore when I bought this car last year I had heat,but anyways.
Over the summer air dam was modified a/c condenser pulled out new radiator new stat new water pump new hoses and I wired both fans to cone on when key is turned.
Now to the heater issue all vents work and operate Luke they should and even though a/c is out when I flip it to cold the air blows colder.
I have bled this sucker and for the life of me the heater core bleeder still bubbles I even rev the motor with bleeder open and got a good stream
I even pulled fan relays out and got temp up to 220 and air was Luke warm
I played with controls and it seems everytime I turn on/off the back on I get some heat but nothing to run home and tell mom about
So any ideas? Places to check?
I smell no coolant temp is barely one notch below half and carpet is dry.
This is a 1993 z28 btw thanks for your help
 
Old Nov 9, 2011 | 09:55 PM
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Hmm maybe bad thermostat or the heater core is clogged.
 
Old Nov 10, 2011 | 05:50 AM
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My guess would be a clogged heater core. That or the plenum that directs airflow over the heater core is not operating properly.
 
Old Nov 10, 2011 | 07:09 AM
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Is it in behind the dash area? I have hit on the black cover

Also am I supposed to hear a flap door when changing the selector for hot and cold cause I do not
 
Old Nov 10, 2011 | 08:14 AM
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Old Nov 10, 2011 | 08:15 AM
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look at number 16 on the list to see how to flush the core.
4th Gen LT1 F-Body Tech Aids
 
Old Nov 10, 2011 | 09:01 AM
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i dont think i have slam but airflow does change

if i flip it though i get heat then it gets cooler im gonna see whats behind door #1 lol
 
Old Nov 10, 2011 | 05:36 PM
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Originally Posted by grabbem88
Is it in behind the dash area? I have hit on the black cover

Also am I supposed to hear a flap door when changing the selector for hot and cold cause I do not
There should be two plenums. One that directs the air out the heater vents, defroster or dash vents, and a second one that controls the amount of air that is forced through the heater core.

The heater core is always going to be the same temp (once the engine reaches operating temps), and the second plenum is controlled by the temperature control **** on the dash. When it is set to hot, it directs almost all of the air to go through the heater core, hence hot air. When it is set to cold, it allows almost all of the air to bypass the heater core, hence cool air. Depending on how you have the temp control set on the dash, more or less air is forced through the core.

So, if you have already verified that heater core is not clogged (Craby posted the troubleshooting procedures), then it must be the plenum controlling how much air is forced through the heater core.

Or, it is possible that the box the heater core is mounted in is clogged with leaves and other debris. I only mention this scenario as my old Jeep Grand Wagoneer was notorious for allowing leaves and other crap to get into the heater box and clog the heater core and not allow much air to flow through it. So whenever I didn't have much heat, I would open up the heater box and clean out all of the crap - then I would be roasting in that rig.
 
Old Nov 10, 2011 | 07:36 PM
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there is a flow restrictor in one of the heater hoses, it may be plugged.
 
Old Nov 11, 2011 | 08:35 AM
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Really? That might be why it won't bleed I just get bubbles
 



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