Hello, my ac got hot in the suburban, had it charged and still hot. i think it was blowing cold in the back, and hot in the front. Now it is hot everywhere. I did an internet search and completed a "reset" by removing an hvac fuse and following the instructions. Still blowing hot. Do i need to replace the actuator blend units (whatever you call them), all of them, or try something else? Also, got a nasty oil leak, either a valve cover, or maybe oil pan. Is a valve cover gasket a pain on these suburbans? Thanks so much.

 

On the valve cover gaskets - I had a 2003 GMC Yukon 5.3L - basically the same vehicle but the shorter version - and my 2006 Silverado 4.8L. I don't think the valve cover gaskets would be too much of a pain to replace. I just pulled up the page on doing this in my Haynes repair manual for the 1999-2006 model years, and it looks like you have to remove the top "Vortec" plastic engine cover, the air filter housing and, some brackets to shift the heater hose, along with the air injection check valves and pipe assemblies (those go into the exhaust manifold). You also have to disconnect a couple of vacuum hoses, and remove the ignition coils, presumably to get the clearance you need. If I had to guess, it will take a couple hours. You can review a detailed manual HERE: https://lemon-manuals.la

On blowing hot, that would be the air temperature actuator. The mode actuator controls where the air blows out, the temperature actuator controls the blend door. The one for the front is up under the dash, onto the the left (driver) side of the black HVAC box under the dash. The one for the rear is behind the cargo area cover on the right rear passenger side.

It would be kind of unusual for BOTH the front and rear actuators to go bad at the same time. I think I would be tempted to remove the actuator and see if you can control the blend door by turning the shaft manually, to see if that makes a difference, before replacing both front and rear actuators. There is always the possibility something is wrong with your climate controls, or even the air temperature sensor that is on the unit. Or else you have a charge, but something is not cooling properly in the system? Are the AC lines cold near the accumulator, back by the firewall on the passenger side, when the compressor is running?

If you have manual controls like my Silverado work truck, then there is no air temperature sensor.

 

If it's hot everywhere, I would 1st verify the components under the hood are working before going after the actuators. Make sure a/c clutch is engauging; you can also feel the lines from the compressor to verify one side is nice a cold.