Avalanche problem

[hunterdan]

Hello,

I just bought a 2004 Avalanche Z71 with the 5.3. Here's the issue...it's a little complicated

OK, during test drive I cranked it up and turned on the AC. It blew hot so I turned it off and just checked out the motor and trans. The engine ran great with lots of power and the trans shifted perfectly. I drove it for 45 minutes getting it up to temp and punching it here and there. I tried the AC a few more times but it still blew hot. After the test drive I told the dealer about the AC so he went out and tried it and it started blowing nice and cold. He thought I had pushed the wrong buttons but I knew I hadn't because I owned one of these before...

I ended up buying it and it drove and shifted fine for 75 miles. All of the sudden it started loosing power like a rag was in the exhaust and then it started slipping a little between 2nd and 3rd. I changed the trans fluid hoping that would fix it but it still slipped between 2nd and 3rd with the engine bogging still.

Last night I decided to disconnect the neg battery connection and reset the computer. When I went to loosen the connection it was really loose and I disconnected it by hand. I waited 15 minutes and reconnected the cable. I took it for a spin and it was running and shifting perfectly with no slipping and lots of power. Funny thing is my AC blew hot for 20 -30 minutes just like on the initial test drive and now is ice cold.

When I came to pick up the truck from the dealer I showed up an hour earlier than I had told them. The hood was up and the windows were all down. I asked if it was blowing hot again and why the hood was up? They said they had just left the windows down for fear of locking the keys in it and the hood was up because the were checking fluid levels. Before I could take possession of the truck they had to take it to TireMaxx and have it inspected. They claimed it had a new battery installed 4 months ago and had not finished it's cycle. I guess none of this last paragraph matters but seems to me that these guys knew there was an issue....

I guess I'm just wanting to see if anyone else has experienced slipping and loss of power due to weak battery or bad connection/ground? I'll update this thread with results after some miles down the road.

Thanks, Daniel

 

[Mac5005]

I'm guessing bc the PCm controls the shifting, any intermittent electrical issues can cause all sorts of weird issues.

The shifting and line pressures are controlled with electronic solenoids, so electrical issue is plausible for the trans issues.

As far as hot air, could be one of door motors.

On my 04 Avalanche, I once got hot air on driver side and cold air on pass side.

I unplugged Hvac fuse under the hood to reset the Hvac system. I then turned key on, but didn't start and didn't push any Hvac buttons. This resets the blend doors and Hvac computer controller thing in the dash.

After I did the reset, it has worked fine.

Dealer wanted $1800 to remove dash, windshield, center console and seats to change the 4 $60 door motors in the Hvac system.

 

[hunterdan]

Thanks, I did the reset and now it is blowing cold on both sides. Turns out after reading your comment ...mine was blowing cold on pass side and hot on drivers side also. Trans is doing good after computer reset and tightening the battery ground.