Hi all,

Hopefully someone has seen this problem before and can help. The HVAC mode on my 1997 Ram 1500 Laramie SLT Cub Cab 4x4 is stuck on defrost with a little bit of air coming from the the floor heater duct. The Heat / AC temperature mode switch seems to be working fine.

Any clues where I should start looking to get the mode selectror switch working again. I suspect its a vacuum issue and I already see that one of 3 lines coming off the vacuum resevoir is plugged with a screw. It's the line that T's right off the top of resevoir. Can anyone tell me where each of these lines should be going and connecting to?

I think a related vacuum issue is that the truck goes into 4 HI and 4 LOW fine, but when I bring it back into 2 HI it takes quite a while (driving) until the front axel actually fully disenages and the 4WD light goes off.

Any and all help, suggestions will be helpful. I did not see much on these types of issues in the Service Manaul. It also did not say where the lines form the vacuum resevoir atatched to.

Thanks

 

My truck is also stuck on defrost so I can't help you much in that department. How long does your 4x4 take to disengage? I know my truck needs to roll in forward or reverse to fully disengage but if we are talking about a mile, then that's a big difference. What about engaging? 9 times out of 10 these types of 4x4 problems are actuator problems.

 

Major leak in the vacuum lines somewhere.
The line going through the firewall with the A/C lines is where mine was chaffed through.
The inline check valves are noted for going bad... this can also be a contributor.