ac low pressure

[47papa65]

ac was not cooling very well. added one can 134-a and now low side reading is 55 at idle. goes down to 45 at 2000 rpm's. is this too high? 1996 rangere v6

 

[97RangerXLT]

45 to 55 is pretty normal pressure on the low side (55 is a tad high) depending on outside temperature. the hotter it is outside, the higher the pressure in the system. I have a temp/pressure chart somewhere...

Something to look at, this is the current problem with my truck. your low side pressure is only half of the equation. check your high side pressure as well. depending on the outside temperature it will be between 150 to 250 usually, and this will fluctuate as the fan comes on etc... My issue is that it shoots up to 350 and still no cooling. makes me think that there is something blocking the expansion valve (possibly a part of a deteriorating hose or o-ring) So my next check will have to be to have the system evacuated and take it apart...

But check your high side pressure as well. you will need a manifold guage set for that. you can get them for about 50 bucks at harbor freight, 90 bucks at o'reillys for a decent one.

AJ

 

[adsm08]

makes me think that there is something blocking the expansion valve (possibly a part of a deteriorating hose or o-ring)

Rangers don't have an expansion valve. They have an orifice tube. And the most common blockage is a blown up drier.

I've found the best way to test for a blocked orifice is a thermometer. If it's blocked the register temp will usually go up when the A/C is turned on.

 

[LearjetMinako]

The A/C system is really simple in design. The compressor is the only moving part. So if your compressor is working, and the system still retains its freeon, then most likely it will be a blockage.

Seeing your truck is a 1994, if the A/C system is orginal, it might be time for a rebuild. Mine is 1996 model, and I've fixed mine twice before doing a complete rebuild of the system. And while I was at it, I upgraded a few parts. Now it can blow 36*F air out of the vents on a 90*F, and is keeping me cool in this 100*F heat wave right now.

 

[47papa65]

yesterday it was 101 here and my truck was blowing 55 degree air after 5 minutes driving. does this sound right?

 

[noahkenny]

Being a professional a/c mechanic something thats gets overlooked is a stopped up evaporator. Autos are not as bad as tractors and equipment but over time the evaporator stacks up with leaves and straw. This will cause poor airflow and vent temps along with low pressure readings on the low side. Most of the time you can remove the blower motor and look up in the housing and inspect the evaporator. You can also remove the blower motor resistor and inspect the coil too. Good chance you will find debris. The older the vehicle, the more trash you will find. Its a good idea to clean it out even though you are not having a/c problems. You will be really suprised how much better the a/c system will work after you do. Debris can also cause a fire hazard by buiding up enough to come in contact with the blower motor resistor and cause a fire. Have seen a few cars burn up from it. The evap coil stops up slowly over time so you dont realize the loss of airflow.

 

[adsm08]

yesterday it was 101 here and my truck was blowing 55 degree air after 5 minutes driving. does this sound right?

High 40s is preferable, but the system will have it's limits. Depending on humidity, 55 at 101 sounds darn good to me.