No heat

[nkostop]

So my 01 Tahoe's heat recently stopped working after a road trip, right when I turn it on, it blows hot for maybe 10 seconds then goes cold, any ideas?

 

[Danny3737]

Could be a partially plugged heater core.

 

[rockola1971]

Have you checked your coolant level?

 

[nkostop]

My coolant level is fine, it's odd, heat works somewhat under load, but not at idle

 

[rockola1971]

Could be thermostat suck open or a problem in the HVAC like malfunctioning blend door. Whats your temp gauge show when its blowing heat and then when its not?

 

[nkostop]

Temp gauge is almost always just below 210, doesn't change after warmed up

 

[rockola1971]

Do you have automatic climate control or manual knobs? Im leaning towards a hvac system problem. A quick and dirty would be setting your controls to max heating and use an infrared thermometer to measure the inlet and outlet temp of heater core. When you have a no heat problem im curious what the temp measurements at the inlet and outlet are at the heater core.

 

[nkostop]

Update.....it's been a while but I performed a total of 3 heater core flushes. The first 2 did nothing then I realized I needed to back flush it. A rather generous amount of pebbles/rocks came out... Heats blowing at 165° now, compared to 65°

 

[SmileB44Death]

Do you have automatic climate control or manual knobs? Im leaning towards a hvac system problem. A quick and dirty would be setting your controls to max heating and use an infrared thermometer to measure the inlet and outlet temp of heater core. When you have a no heat problem im curious what the temp measurements at the inlet and outlet are at the heater core.

I’m having the same problem but my defrost doesn’t work to. Both of th heater inlet/outlets were cold after a 40 min drive and operating at the right temperature

 

[rockola1971]

I’m having the same problem but my defrost doesn’t work to. Both of th heater inlet/outlets were cold after a 40 min drive and operating at the right temperature

If your inlet hose is cold too then my guess is that you are real low on coolant.