1996 tahoe weak heat/ flow

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Natedawwg

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I have the driver and passanger side actuators replaced new heater core stat coolant temp radiator hvac control panel and the heat/flow is still not that good
 

JeremyNH

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You didn't mention the blend door. Passenger side is the recirc door (air source selecttor inside/outside the cab) and the drivers side is the mode door (directs blower discharge to upper vents, lower vents, defrost, etc). The blend door is in the middle of the dash mounted on the heater box. It controls the mix of hot and cold air so how hot or cold the air from the vents will be. Same part as the recirc door actuator. I had to replace mine a few years ago. Took the old one apart and found the main drive gear was cracked.
 

Natedawwg

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So i replaced the blend door and watched it move with adjusting temp.
I also put a new heater valve/ solenoid with 2 vac lines yesterday i have vac and power 14v on white but .(008 - 0.010 0.011 0.013 .014 consistant )on black i tried jimmy'ing it around to see if it was a chaff or break but no fluctuation it seemed normal almost from .(008 to .010 to 0.11 .013. .014)(still consistant)but nothing when jimmying it around like still read .008 to .014. When turning to cold i belive the plunger is suppose to suck in on heater valve but mine does not but i have vac and power so im a little confused. Im assuming the blend and the heater valve/solenoid are some what connected and i think its mixing hot and cool air also thinking does the gear that the blend door mounts to is bad not just gear but the whole mechinisim that sits in that box ? Also the stat does seem to work opens 1 line before 210 and drops 1.5 lines. 195 stat 16 psi cap i also noticed the coolant looking into the radiator does not flow at all from driver side to pass. Water pump does work and it does not over heat. No vac leaks
 

Natedawwg

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A/C evaporator plugged with debris?

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Weak electric power to HVAC blower motor?

Weak, aftermarket blower motor?

Blower fan not securely attached to blower motor shaft?
Is there a mechinisim behind the blwnd door?
 

east302

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So i replaced the blend door and watched it move with adjusting temp.
I also put a new heater valve/ solenoid with 2 vac lines yesterday i have vac and power 14v on white but .(008 - 0.010 0.011 0.013 .014 consistant )on black i tried jimmy'ing it around to see if it was a chaff or break but no fluctuation it seemed normal almost from .(008 to .010 to 0.11 .013. .014)(still consistant)but nothing when jimmying it around like still read .008 to .014.

Going by memory here, but the solenoid should just have a voltage and ground to it. If you have vacuum to the heater valve when the panel temp dial is in the “MAX” detent (and no vacuum when it isn’t) then it sounds like the solenoid is working correctly.

When turning to cold i belive the plunger is suppose to suck in on heater valve but mine does not but i have vac and power so im a little confused.

If the spring-loaded plunger on the valve can be moved up and down with marginal effort, then the valve is likely fine. Are the vacuum lines connected correctly on the solenoid?

Top line is from the PCV fitting, bottom one goes to the water valve.

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Im assuming the blend and the heater valve/solenoid are some what connected and i think its mixing hot and cool air

The valve only closes to shutoff coolant flow to the heater core to maximize a/c performance. If the plunger is down, the valve is open and shouldn’t impact coolant flow provided that the hoses are correctly installed.

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thinking does the gear that the blend door mounts to is bad not just gear but the whole mechinisim that sits in that box ? Also the stat does seem to work opens 1 line before 210 and drops 1.5 lines. 195 stat 16 psi cap i also noticed the coolant looking into the radiator does not flow at all from driver side to pass. Water pump does work and it does not over heat. No vac leaks

The blend door just sits in the box, no gears or anything. If the position indicator dial on the actuator is turning smoothly, then that should rule out any binding in the box.

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Natedawwg

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Going by memory here, but the solenoid should just have a voltage and ground to it. If you have vacuum to the heater valve when the panel temp dial is in the “MAX” detent (and no vacuum when it isn’t) then it sounds like the solenoid is working correctly.



If the spring-loaded plunger on the valve can be moved up and down with marginal effort, then the valve is likely fine. Are the vacuum lines connected correctly on the solenoid?

Top line is from the PCV fitting, bottom one goes to the water valve.

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The valve only closes to shutoff coolant flow to the heater core to maximize a/c performance. If the plunger is down, the valve is open and shouldn’t impact coolant flow provided that the hoses are correctly installed.

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The blend door just sits in the box, no gears or anything. If the position indicator dial on the actuator is turning smoothly, then that should rule out any binding in the box.

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you have vacuum to the heater valve when the panel temp dial is in the “MAX” detent (and no vacuum when it isn’t) then it sounds like the solenoid is working correctly.
So i have no vacume at the valve i have it at the solenoid on the fire wall i switch from hot to cold on max and the plunger does not go up. Im going to double check to see if anything bindes. I did see it move all adjustments the ac evaporstor got some debri in it not giant but i cant get a light in there and try to see through it withouth taking dash out
 

east302

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If the plunger is down, the valve is open and coolant will circulate through the heater core. Possibly a hole in either the vacuum lines to or from the solenoid, but if you’re chasing a “good air flow but low heater air temperature” problem then the open valve isn’t going to be an issue unless the hoses are on wrong.

Meaning - you only want that valve to be able to close if you want to block coolant to the heater core to increase a/c cooling performance. That’s all that it does, it’s either open or closed. It doesn’t modulate coolant flow to the core or have any control over heater performance when it’s open.

If the interior components of the system check out (sounds like they do), and you’re getting cool/warm air instead of hot, then I’d be looking at coolant flow.

How hot are the hoses at the firewall? Make sure the hoses are installed correctly at the water valve since they “look” kind of wrong when they are installed right.

If the air temperature is sufficient but air flow through the vents is not, then there’s a restriction at the evaporator, the blower is weak or air is leaking out of the air box sections…foam insulator bad, rubber edges of dampers are rotted, air box case is broken, etc.
 

bretcopsey

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i also noticed the coolant looking into the radiator does not flow at all from driver side to pass. Water pump does work and it does not over heat. No vac leaks

My 95 3500 ran at normal temp and would hardly put out any heat from the heater last winter. This past summer I used Prestone flush with distilled water and drove it that way for a few days. After this there still was barely any flow trickling out the tubes when looking into the radiator with cap off and engine running.

So, I drained the radiator and refilled with fresh distilled water and more flush for round 2 and left it idling in the driveway, radiator full enough to cover all but the top most rows of tubes and cap off. It took a couple hours, but the scale was eventually eaten away and the water flowed freely through the tubes. My thought process is if the radiator was that bad, the heater core probably was too.

For good measure, after draining round 2 of flush from the radiator, I also flushed the heater core through both hoses with a garden hose, what came out looked like mud but it eventually flowed clear. I also used the blow gun on my compressor to blow out the inside of the evap box.

Lastly, I disconnected upper and lower hoses from the radiator and removed the thermostat, then reinstalled the thermostat housing and upper hose on the intake. I then placed the garden hose in the upper rad hose and ran the engine for a few minutes with the lower hose feeding into a storage tote. Picture is the crap that came out after 2 flushes were already done.

I was dead set on trying everything I could think of to avoid pulling the dash to replace the heater core. And I’m happy to report that it worked and this winter the heat is so good I can’t keep it on high once the engine is up to temp.
 

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