So I have a vacuum issue affecting the A/C...

[Dredwolf]

Mainly the blend and fresh air door regulators, since when accelerating, Air stops blowing from the vents. And sometimes it takes a couple of tried to get the airflow to move from defrost to the vents. Blower motor works all speeds, I have A/c and heat.

Before I tear into this thing, I don't mind having parts on-hand I may not need, it beats multiple trips to the parts storer. If anyone has a suggested parts list, please reply with it.

[XJ Wheeler]

I've had the same problem with mine for a couple years and i'll be interested to see what others say.

Its going to be vacuum related. The default setting for loss of vacuum is defrost, that's why it goes to defrost and not to vent under acceleration.

Sent via messenger pigeon - i talk, he types.

[4.3LXJ]

You just have to eliminate vacuum leaks. Easier said than done. Check the vacuum reservoir first. Then the hoses for cracks

[Dredwolf]

PO tossed the ball reservoir when he added the "killer thump system, with HUUUUGE battery cables", but i found one at the local u-pull and installed it, before crafting one from PVC.

Still had the issue, no change. I guess check/change all the lines under the hood first, coming back from the reservoir?

Are any of the regulators more problem prone than the other?

A/C is ICE cold in this XJ, with little heat issues so far, so I want to try and make this thing work.

[4.3LXJ]

I would start from the intake manifold. That seems to be where you get cracked lines at

[ParadiseXJ]

I would be looking for (as 4.3XJ says) from the rear half of the intake manifold...a 3/8" hose out of a brass nipple that runs from there to the vacuum reservoir. That is the ONLY vacuum source for the HVAC and the cruise control. Then check all the lines to and from the vacuum reservoir all the way up to the firewall.

Replace any hoses and/ or check valves if they are at all compromised (chafed, cracked etc.). Don't tape up the vac lines...Just buy new bulk vac line...it's cheap. The vac lines under the battery tray are the usual suspects.