Multitude of issues on my 98

I know its a no no to post in both forums but Im not sure where this issue fit best. Mods if this fits on tech forum better than the other please do what you will

Ok 1998 SE 4.0 with AW4 trans.

I have some issues all may be related but they more likely unrelated lol.

First I have a voltage issue with my compressor running. At stops my voltage falls from 14 to around 9 and lights dim at night. Headlights, dash lights etc and the jeep will start to idle poorly. Also as I come to a stop I notice my rpms will pick up a bit then drop down, sometimes multiple times before smoothing out. Start moving all is well with this issue until randomly it happens again at another light.

Second, with my AC on my braking seems to have changed from good to pretty stiff, almost as if there were a vac leak. the booster seems to lose some of its effectiveness.

Thirdly my jeep will have a slightly erratic idle during normal operation. I noticed today that it seems to clear up quite a bit when my ac is in the on position. With ac off it wants to idle around 600 with ac on around 750. The jeep also struggles to heat the cabin with heat on full blast, it does warm up a little when in motion but the heat cools off at stops and at idle.

I am thinking I must have a vac leak on something controlling the hvac system that gets nullified as the rpms increase. It also must be nullified or minimized when the high idle kicks on when the ac is switched to the on postion.

These issues are driving me batty! It seems the voltage issue is from a bad ground/bad positive bat cable that I know about but the other issues are driving me nuts.

How do you smoke test an engine to find a tiny vac leak? How about the part of the ac that the vac lines go into with the little diaphram near the firewall? Are those prone to fail and leak? Recently the jeep has been a taking longer to start than normal when cold, but fires up instantly when warm. It runs strong and evenly though all rpm ranges except that issue with the idle. Im stumped!

Little help here lol

Thanks!

Vacuum leaks can be found with water, spray and listen for the idle to change.

It is normal for the idle to go up when the AC is running... Hunting for idle speed could just be a dirty IAC. Easy to remove and clean. If the IAC is filthy, I would reccommend removing the TB and giving it a bath. Remove the sensors prior to cleaning so as not to damage them with the cleaning chemicals.

If the booster is leaking, the brakes go soft.

A faulty T-Stat will prevent the heep from getting to temp properly.

Voltage dropping.... Start with the grounds. I have a dedicated ground running from the Alternator directly to the battery. Most likely an over kill but... If the grounds do not get it done, remove the alternator and have it tested. Short list of problems to be had.

Thanks for the response o Gauge!

So far I have Cleaned the TB and IAC, replaced the tstat with a staun 195 and the rad cap.

I am going to have the alt tested tomorrow.

Is there a way to check the booster? I know alot of guys pull the booster hose and listen for air to rush into the booster.

Gahhhh!