A/C problem

[Richard 91]

I just replaced all the components under the hood on my a/c system, I brought to my local repair shop to get the a/c system charged. The compressor is not receiving any power.  I started trouble shooting and when  I turned on the a/c to max and turned on blower, the air only comes out of the defrost and not the vents.

 

Any tips on fixing that problem.

 

[eaglescout526]

4 minutes ago, Richard 91 said:

The compressor is not receiving any power.

 

Did you check the relay?

 

4 minutes ago, Richard 91 said:

I turned on the a/c to max and turned on blower, the air only comes out of the defrost and not the vents.

 

How does your vac lines from the canister under the bumper t the fire wall look?

[phatton]

The air vent system is vac. controlled - if the system looses vac. - air only comes out of the defrost.  If you pull the radio, you can see if the vac. line to the switch is attached .

 

[OldManComanche]

There are several air gates under the dash that direct air to different air vents. Engine needs to be running to provide vacuum to dashpots to open or close them. eaglescout526 is telling you to look for vacuum leaks.

  LOOK FOR

  AC fuse blown, the fuse is 25 amps and I have seen several that weren't making good contact in the fuse box 

  Wires not hooked up / bad connection to the low pressure switch

  Check the AC relay, is the relay getting power, is it working? 

  Run 12V to the AC compressor to see if the clutch works

   A list of all of the parts you replaced might help.

[Richard 91]

thanks for the tips I know my vac lines are rooted I will change them.

[Richard 91]

I have the dash apart but cannot figure out how to remove glove box the white vac line coming out by coolant lines is no good trying to find where it comes through fire wall.

[eaglescout526]

Glove box isn't removable. Youll have to remove the whole dash.

[ghetdjc320]

On 7/11/2020 at 8:08 AM, Richard 91 said:

I have the dash apart but cannot figure out how to remove glove box the white vac line coming out by coolant lines is no good trying to find where it comes through fire wall.

No need to go that far into the system unless you want to replace the evaporator core. Just check for vacuum going through the firewall where the ac lines connect to the expansion valve. That vacuum line feeds the vacuum for the hvac switch panel. 

[Richard 91]

where does the vacuum lines go to that are located by the expansion valve an how do you get to them?  Needed to leave this undone while visiting my new grand baby.

[eaglescout526]

One line goes to the heater valve and the other line runs to the vac reservoir behind the front bumper on the passenger side. I believe the gray/purple one goes to the vac cannister and the black should go to the heater valve. Youll have to see if your vac lines are still present and haven't been dry rotted out.

[Richard 91]

where do they plug into under the dash and how do you get to them?

[eaglescout526]

They all route to the back of the AC control deck.

[Richard 91]

Thank you for your help

 

[eaglescout526]

No problem. 

[Richard 91]

I JUST GOT MY TRUCK BACK FROM THE SHOP, THEY HAVE SERVICED THE A/C GOOD NEWS NO LEAKS BAD NEWS IS THE LOW PRESSURE READS HIGH AND THE HIGH PRESSURE IS LOW, MECHANIC THINKS THERE IS A BLOCKAGE SOMEWHERE. ALL HOSES, COMPRESSOR, DRIER, EXPANSION VALE AND CONDENSER  ARE NEW AND I BLEW OUT THE EVAPORATOR  COIL WITH AIR. THE ONLY THING I CAN THINK OFF IS THE LINE WITH THE MUFFLER ON IT WAS REBUILT BY JEEP AIR SO MAYBE THE MUFFLER IS CLOGGED. ANYONE WITH OTHER IDEAS?

 

[MJCARENA]

Do you have any actual readings from the gauges? 

[zomeizter]

Low pressure high and high pressure low, as in both pressures are the same or close to the same, means you have a bad compressor. Was the expansion valve replaced? It could also be clogged. Were all lines flushed to include the condenser and evaporator?

[Minuit]

Need gauge readings to be able to tell anything.

[Richard 91]

If this storm does not hit us Monday I will bring it back to the shop and try to get some numbers before they evac the freon out. To answer one question the compressor and expansion valve is new.

[silvertwinkiehobo]

You say the pressures are not in spec, but did you have any cooling at all? And, is the system set for R134a?

[silvertwinkiehobo]

A good system drops air temp at the central air vent about 40 degrees from ambient,, when the doors are open and the control is on maximum. If you have some cooling, but not what you should have, I'd think the system is over-oiled. Sometimes, that can happen. One tech does one thing, adds oil but doesn't tell anyone, the next tech adds more, not knowing it's already been done. Or, a compressor comes pre-oiled and someone adds more. Another thing to check is if the compressor had oil added to it but not cycled through by manually turning the clutch plate and shaft. I usually install the freshly oiled compressor, hook up the lines, then hand-turn the clutch plate to run the oil through the cylinders and out to the discharge line.

[purvis307]

I just joined the forum yesterday and this post was exactly what I needed Thanks a lot guys . I just bought my first MJ and I love it. Lot to learn.  

[purvis307]

89 Comanche.

[Jeffery Starn]

Check the vac system in the dash 

[Richard 91]

Well the a/c system is blowing cold air. I found a clog at the expansion valve, little bits of rubber was packed in there pretty tight. I still have to fix the vacuum leak, trying to find a new vacuum harness but that looks hopeless.