Heater just stopped working.

[Tengo1]

Just in time for the cooler morning drives to work this fall….

06’ H3. AC works fine. System blows air fine and increases and decreases as it should when turned up and down. System switches between floor, dash, and window as it should.

I noticed about a week ago when I drove to work the AC was still on from the night before and was freezing me out because it was around 50 degrees outside. I turned the AC off by hitting the button and cranked the dial to heat. After about a mile of driving I realized it wasn’t getting any warmer. Hit the AC button on and off a couple times and cranked the dial from hot to cold to hot again and it finally kicked on.

Today as I was driving to work it was cold again. Did the crank back and forth and nothing. AC button on and off, nothing. Never got it to actually blow hot air again.

Thermostat was replaced in 2015 and seems to be running as normal. Running temp is where it should be. Both heater hoses in the engine bay are hot to the touch. Again, AC works fine and blows cold.

I did the actuator calibration procedure I found I online. Listened to it as it went through all the changes. But it’s still just blowing cold.

I’m assuming it’s a bad actuator. Any thoughts? And is this a job I can do myself? What else should I test to ensure I have the right culprit?

 

[Happy Hummer]

Possible causes heater core clogged?
I agree though that it sounds like electronic issue.

 

[Tengo1]

My understanding is that if the heater core was plugged one of the two heater hoses would be cold. Both are hot.

 

[Jeepwalker]

1) Have you ever put regular water in the cooling system (unpurified)? Even with new anti-freeze coolant? Like tap water? If you have, that could be an issue. If you remove your radiator cap and look inside and see ANY mineralized build-up on coolant tubes, that tells part of a story.

2) Have you looked in the GM manual (Schwartzky website), to see if there are tests in the HVAC section to zero in on the hvac system problem? It might also indicate which actuator is failed (if one has occurred). They commonly fail on Jeeps ...I've replaced several. Sometimes it's not the motor that fails, but the cheap plastic end of the motor assembly cracks where it hooks to the heater box door shaft. When that happens, the motor reaches an end (say..closed), and can continue to rotate (slip on the shaft) when the damper door reaches it's seat. If that happens, the unit can't calibrate to determine where open and closed really are. So, sometimes an actuator motor can be working but not really positioning accurately (if the motor end has cracked). The heat/cool damper door has to close nearly 100% or the air won't be very warm. Now ...I don't know how big of an issue this is with H3's specifically. But in the automotive industry as a whole, this is a common problem with HVAC actuators. It's a classic case where if they'd spend another 5 cents in material they could have prevented tens of thousands of headaches and unnecessary repairs.

3) One can still have hot hoses and a heater core that's not flowing as much as it could. It's surprising that if you reduce the engine temp a little, or reduce coolant flow a little, the amount of reduced heat seems to be logrithmically less. And worse yet, if the flow is reduced in the center of the heater core vs the outer edges, you're still getting some flow, but not as much heat transfer at the part of the coil where you need it most. Heater core water passages are very fine so it' doesn't take much in the way of mineralized deposits to cut/reduce flow.

4) Backflush: If it doesn't turn out to be the blend door motor, You could try back-flushing the heater core. House pressure water hose pressure in reverse. Sometime crud can build up and a good back-flush can dislodge it. I've personally had a lot of crud come out of a heater core when backflushed. And the worse one I remember wasn't even a heater core that was 'plugged'. Wife's car at the time. But the difference it made in heater output was dramatic. If that didn't bear fruit you could rig a system and pump engine flush through the heater core. A cheap submersible pump from Harbor Freight in a small bucket would work.

Or flush the engine but use purified or RO water upon refill. Or buy pre-mix Dex-Cool.

 

[Tengo1]

*Update. It was the lower right actuator. After watching a YouTube video I stuck my phone camera down there and filmed while I turned all the controls. Watched the video after and sure enough the other two you could see turn, the bottom right never moved. Bought a new one at Autozone for $32 and threw it in. Ran the calibration procedure. And boom. Issue fixed.

 

[Jeepwalker]

Nice!!

Just in time for cold weather (if you can call NV weather 'cold' -- ha ha)

 

[RamRod]

*Update. It was the lower right actuator. After watching a YouTube video I stuck my phone camera down there and filmed while I turned all the controls. Watched the video after and sure enough the other two you could see turn, the bottom right never moved. Bought a new one at Autozone for $32 and threw it in. Ran the calibration procedure. And boom. Issue fixed.

Thanks for the update, glad to hear you were able to get it fixed. All too often these threads are not updated with the fix.

 

[Wild Bill]

Great! My H3 is doing the exact same thing. I back-flushed and all the other coolant related possibilities and I am certain it is a bad actuator. Bottom right one, huh? I'll have to try the camera on the phone trick. Did you have to remove the driver seat to get to it? Asking for a fat friend. ;-)

 

[Jeepwalker]

You can either see the drive motor by looking under the pass side dash ...or, I can't remember, ...if not you can drop the glove compartment. But look first though. No don't need to remove seat.