GMC 3500 w/7.4L CC lb heater problems

[cigarman63]

My 98 heat stopped working. I flushed the heater core,but I couldn’t find the heater control valve. I had it sitting next to a 7.4 97-99 3/4 ton suburban with the hoods up. The suburban had the valve in line with the heater hoses, mine just has the hoses going into the firewall. Could there be another location?

 

[454cid]

My 98 heat stopped working. I flushed the heater core,but I couldn’t find the heater control valve. I had it sitting next to a 7.4 97-99 3/4 ton suburban with the hoods up. The suburban had the valve in line with the heater hoses, mine just has the hoses going into the firewall. Could there be another location?

You don't have one in the truck. If the engine is getting up to temperature, I'd suspect the blend door is not moving.

 

[movietvet]

Is it blowing? If is blowing, is it cold instead of warm? If is, then could be a blend door actuator or control head.

Can you get an infra red temp gun reading of the inlet hose at firewall, that would be the hose closest to engine and a temp reading at the outlet hose. How close in temp are they?

 

[618 Syndicate]

You don't have one in the truck. If the engine is getting up to temperature, I'd suspect the blend door is not moving.

+1
I've never seen a heater control valve in any of the 3500's that I've owned. Someone added the one in that Burb.

 

[454cid]

+1
I've never seen a heater control valve in any of the 3500's that I've owned. Someone added the one in that Burb.

I think the Suburbans did get them. I think Hotwheelsburban has mentioned it before.... could be a dual HVAC thing?

 

[618 Syndicate]

I think the Suburbans did get them. I think Hotwheelsburban has mentioned it before.... could be a dual HVAC thing?

It's possible.

 

[HotWheelsBurban]

I think the Suburbans did get them. I think Hotwheelsburban has mentioned it before.... could be a dual HVAC thing?

Yes it's a Burb thing. If Tahoe/Yukon 4 doors had rear air and heat, they should have them too. But the pickups never had them. So the coolant is always running through the heater core, and in hot climates this does affect the AC system performance. The square body trucks had this same basic setup, and Dad used to put a manual shutoff valve inline. Made the AC cool lots better in the humid SE Texas summer....