Drop Axle Issues on New t800

I just bought a Kenworth T800 Quint axle dump truck. I got it from an auction so I have no prior history.

The drop axles seem to have a mind of their own. I can't get them to do what I want. I released the parking brake and they all went down. But now I cant get them to go back up. I tried putting it in reverse, tried flipping the axle switches back and fourth and no luck.

Hoping to find someone who has some experience with these. Not really sure where to start troubleshooting.

Thank you

 

Yes. I let the truck build 100+ psi. The driver that delivered my truck said it took a really long time to build air but it’s building fine for me.

I did drain all my tanks and had a lot of water in a couple of tanks. Made me think that I could have ice built up somewhere. But it was 50 degrees here yesterday so I thought it would have thawed out.

 

I pulled the dash panel and the switches look to be air operated. There’s an air line on each side of the switch. No electrical wiring.

 

this is super helpful!! Thank you

I think I could have a combination of problems. My truck is suddenly not building over 90 psi. But I can’t hear any leaks anywhere. And my air tanks are humming, I wonder if my air dryer is failing. It has a brand new filter on it But the dryer itself is old

I did find a couple of rips in some of these airbags on the lift axles too.

I’m gonna check all these valves that you pointed out.

 

I had a spare compressor governor sitting in my garage. So I swapped it out. I started it up and The truck was airing up to 120. The air has to be above 110 for the axles to go up and down. But once the truck is fully aired up, the axles are working. I’m not used to air bags and forgot how much PSI they need to operate.