A/C Won't Work

[ThatDrummerGuy95]

Okay guys, I'm 16 and new to this whole thing. I have a basic background knowledge of mechanics. I have a mechanic/welder for a father and I'm going to school for mechanics so it's a learning process. The A/C on my 97 Tahoe LT won't work. I replaced the compressor and gave it multiple freon shots. Could the lines be bad or am I missing something? All help is greatly appreciated. Please and Thanks, -Jesse

 

[DRAGGIN95]

It could be one of your pressure switch's, it could be low on freon, it could have no power, have you tried jumping across the low pressure switch on the dryer to force the compressor on?

 

[67chevymechanic]

Did you also replace the accumulator and orifice tube as well? If not, you should. Then pull a vacuum on the system for at least 30 minutes. I prefer 45 min-1 hour. (this pulls all the moisture out of the system). You can rent a vacuum pump and gauges from the parts store to do this. Then, let the vacuum suck in the freon until it won't take any more. That'll be enough to make the compressor kick on. Keep charging until you get a good cold sweat all the way to the compressor on the bigger line (low side). *When you're doing this, have the A/C on max, fan on hi, and I like to put the windows down.* This makes it take the most freon it can. If the compressor still doesn't kick on, I would investigate the low pressure switch, located on the accumulator. Good luck!

 

[ThatDrummerGuy95]

I haven't done any of that, I appreciate the advice! Thank you!

 

[Tempted]

Did check to make sure the pressure switch was hooked up? One way to determine if the switch is fouled is by simply jumping it. Unplug it, run a jumper wire in a loop and turn your AC on. The compressor WILL kick so long as it is operational. If the air doesn't blow cold then you have an AC mechanical failure. If it does blow cold, you have an electrical failure(switch).

 

[Tempted]

And I forgot to mention, many times when you fill a system it will not accept a charge at all until you do jump the switch.

 

[67chevymechanic]

...many times when you fill a system it will not accept a charge at all until you do jump the switch.

I mean no disrespect to you Tempted, but this is one of the reasons why you pull a vacuum. One to get the moisture out, and the other so you don't have to jump the switch. Just let the vacuum pull as much refrigerant in as it can and that should be enough to let the compressor cycle on and off. They usually turn on around 50-60 psi on the high side. BTW, my system takes about 4 12oz cans to fill it up.

On a side note, I have had some picky systems where I had to jump the switch to make them take anything. I usually plug the switch back in when it gets to 75 psi on the high side and let the switch take over again.

I guess everyone has their own way of charging an A/C system. It's kinda like asking 3 people how they change tie rods. You get 3 different answers. One guy whacks it with a BFH, the other one uses an air hammer, and the last guy uses a tie rod separator. lol.

 

[Tempted]

I understand, but he added cans and didn't pull a vacuum. That is why I suggested jumping the wires.

 

[67chevymechanic]

Gotcha. I've seen my boss charge up cotton pickers and tractors without pulling a vacuum. It does work in a pinch when the equipment is out in the field and there's no electricity around. And then when he charges from the 30 lb cylinders, for some reason he ONLY puts liquid in them. Then wonders why the compressors go out so quickly. While all the systems I've charged are still cooling.

 

[ThatDrummerGuy95]

Haha, I'll have to try this out when it warms up a bit. Thanks guys!