Hi I have a very weird case of wild vents, I know this has been posted before but my case is different. I have a 1996 5.2l 1500 reg cab, when in park I can rev the truck up and the vents don't go to defrost, and in 1 gear usually it doesn't go into defrost but in higher gear (especially on the hwy) it switches to defrost. I have changed the check valve, I have added a check valve to HVAC control. I have added a vacuum tank after the check valve on the keg, I removed since it didn't fix anything. I don't know what else todo, I don't think it's a vacuum because cruise works and the vents work at idle or in park. Thank you for any suggestions I'm really lost.

 

Put the tank after the check valve for the HVAC controls. It's still the same old problem, losing vacuum on larger throttle openings. In higher gears, you put more of a load on the engine for the same acceleration rate, hence, less vacuum. I don't think you can ever get rid of it completely.... but, the additional tank will help mitigate the symptoms.

 

So no there is no way to completely remove the issue? I couldn't find the factory vacuum reservoir?

 

No not really. The factory one is under the cowl

 

Yes there is. With electric vacuum pump.

 

Exactly. That would permanently solve the issue.

 

Or eliminate as much vacuum dependant things as possible. I used an electric cruise control from another ram in my truck I sold.

 

Seems a little crazy to install a vacuum pump on a gas truck? How much would the canister after the HVAC check valve help? Will I see little difference with the canister, the vacuum pumps seem to be a bit pricey for my taste and I don't like all that stuff under the hood, also did all early gas 2nd gens have this problem off the dealership lot?

 

Yes but 98 and above had a TSB issues where they installed a check valve that has a mini reservoir in it on the HVAC line

 

Yep, it's a common problem as the trucks aged. I don't think they originally came with two check valves, may have come with none..... don't know. Will the additional canister make a difference? Depends on the size. Bigger it is, the less of an issue it will be. Might even be able to find room under the cowl to mount it. So, out of sight.