Fixing a Vaccuum Leak?

[behemoth]

Alright, today we managed to fix my 4x4 by clearing out a blockage in the vaccuum line.

Now my AC compressor turns on and off.

I read somewhere that this can be caused by:
a bad relay (dobut it)
too low freon (doubt it)
vaccuum line being exposed to normal air (sounds about right, considering we took the lines off to fix the 4x4)

How do i re-vaccuumize (definitely not a word...) the vaccuum system?

[olinar]

I haven't a clue but I will definitely recommend a Haynes manual. Best $15 bucks I ever spent for my truck.

[skife]

check the autozone website for their "z-net" thing, they have vacuume diagrams and stuff.

[drg]

You need a vacuum pump.

Note several things ...
- Low refrigerant indicates a leak but it doesn't necessarily mean you have zero pressure in the system.

- How fast does it cycle on and off? A system that can't hold pressure would cycle extremely quickly, if it could cycle at all, I believe.

- A system with zero pressure can be invaded by normal air, which contains water, which can corrode the system internally and compromise the oil in the system.

- You really need to pull a proper diagnosis with an AC gauge set before you start fixing anything.

[Lohman446]

Very few modern AC systems use vacuum to control the AC compressor - vacuum to control the climate control system under the dash sure, but very few use vacuum to control the compressor. Most use an electrical AC clutch to effectively turn the AC on and off.

Vacuum (as you are thinking of normal vehicle vacuum) and the AC system pressure are not related.

[mustangii]

year, make of truck?

many modern vehicle have done away with vacumn controls on the ac. They use motors to open and close the doors in the hvac housing. If this is an older vehicle, like say an 02 and older dodge truck vacumn leaks will cause the ac/heat to cycle from floor to panal to defrost when vacumn drops, as in wot operartion, or going up a hill with the cruise on. Sometimes the criuse will even drop out because of low vacumn. The ac will short cycle because of low refrigerent because of the low presure switch. Vacumn has no control over the operation of the compressor cycling.

edm

[behemoth]

Alright.

That was just my guess, heres the whole story...

AC works two days ago.

Yesterday, take the truck (99 Chevy Blazer) to work to change the shocks. We get the shocks done, and my boss wants to look at my 4x4 (it hasnt worked since i bought the truck.)

We play with the vaccuum lines to fix the actuator, and get it to work. ( i was happy)

So, i'm thinking it has something has to do with the vaccuum lines, because after a little google fu, i find that the AC compressor will cycle on and off repeatedly if the vaccuum lines have been exposed to normal air pressures, the refrigerant is low (which i doubt because when it DOES kick on, its cold as ever.) or something electrical has been damaged. Well, we didnt do anything electrical, so i'm guessing the vaccuum lines.

We DID have to remove the battery in order to get to the 4x4 actuator, but i dont think that could've messed up anything electrical, because everything else works fine...

I dont know...

Also another question while i have you guys here...

Can a battery "pulse"?

I've had a small issue with all my lights on my truck flickering, and the voltage meter doing its little side-to-side dance while this happens.

I've always thought it was the alternator, simply because it seems to flicker in and out while the engine is turning, you can hear the engine going and the lights flickering in synch.

But then when we took the battery off to check the 4x4, we kept the car idling on the alternator with no battery attached, and the lights didnt flicker at all, so i'm wondering if its the battery (i replaced the terminals, but it still does it...)

[drg]

I am not sure about the use of "vacuum" here. Vacuum as regards typical vacuum-actuated components in a car refers to engine vacuum, which is constant as long as the engine is running. However the AC refrigerant is in a separate closed system which is under pressure.

So a temporary opening of the engine intake system to air (i.e. a vacuum leak) causes no lasting effects, but may make the engine run poorly until it is closed. If the AC system is compromised, that is a different story.

Generally speaking you can diagnose just about everything wrong with your AC system's functioning by using the aforementioned AC pressure gauges. Start with that.

[bornl33t]

well you're problem is acutally the vehicle. Blazers are well know as problems.

[MANN]

well you're problem is acutally the vehicle. Blazers are well know as problems.

lol.

ohhhh. you are talking about the competition problems they give to ford's exploder.

[MANN]

We DID have to remove the battery in order to get to the 4x4 actuator, but i dont think that could've messed up anything electrical, because everything else works fine...

Can a battery "pulse"?

I've had a small issue with all my lights on my truck flickering, and the voltage meter doing its little side-to-side dance while this happens.

there is a bad ground on some blazers from the computer (GM bultin). I can get more info on it if you are interested, but it sounds like you have electrical problems somewhere.

[skife]

i'd try a different battery first.

same lights flickering thing was happening to my toyota.

[bornl33t]

lol.

ohhhh. you are talking about the competition problems they give to ford's exploder.

ya know, I have no clue about explorers. all I know is that those 90's blazers were crap. for the record I own chevy, ford and dodge. So don't go there.

[MANN]

ya know, I have no clue about explorers. all I know is that those 90's blazers were crap. for the record I own chevy, ford and dodge. So don't go there.

hmmmm. my 96 blazer has 240k miles on it. Not sure what blazers you are talking about, but the 95+ models imo are some of the best small suvs on the road.

[bornl33t]

Good for you! My brothers cause fire when the clutch on the AC seized throwing the belt into the compressor. Then resulting fricktion caused a total loss. You got a lucky one!