A/C presure High

Hey guys,

Got a problem.
My A/C does not blow cold air anymore. 2000 5.3. I went to Advanced Auto and bought the recharge kit. The directions says to put the hose on the lower preasure side, except there is no valve on the low preasure hose. So I put the dispenser over the only insertion valve I see while the engine was running just like the instructions wrote. But when I put the dispensor the gauge showed about 150 PSI (red zone), probably because it is the high preasure hose, and not to add feon but I had a more serious problem.. My question, what could it be? Where is the low preasure insertion valve?
Any ideas? I am not very familiar with A/C systems in general.

Thanks in advance

Low pressure hose should be right below the high pressure hose. The connection on the recharge kit should only fit the LP side (bigger connection, covered w/dust cap). Did you have to force the connection on?

The problem is that there are two ports what appears to be on the high pressure hose and no ports on the low pressure hose. The low pressure hose is the larger hose, correct?
I placed the can on the only port it would fit and that is what read the 150 PSI

For a 2000 truck to not blow any cold air I might assume there is a leak. Air in the system can cause high pressure. Having said that, I don't know if I would trust that gauge either. Look for any oily residue all around your ac lines and fittings.

Everything looks good as far as no oil residue.

It sounds like you have a leak. 1st you need R134A not freon. 2nd find the low side of your system. The low side valve is smaller than the high side. Start looking at the compressor. The high side has smaller hoses. The low side has larger hoses. Find the plastic cap on the low side (smaller fitting). Connect the R134A bottle to that side.

Like I mentioned before.. there is no cap for the low pressure hose, or at least I can not find it. The High pressure hose has 2 caps.

If the caps are right on top of the compressor the smaller one is the low side.

Silverado is right and I have the same setup in my 03 cheby. I am going to watch this thread incase someone with knowledge of recharging and the location of the lowside valve for these trucks. I was advised that that switch on the acumulator might be faulty. I get ac at first start and goes off occasionally just to be irritating. Almost ready to go to the stealer to get answers.

I will check the next 2000 I see.

Like I mentioned before.. there is no cap for the low pressure hose, or at least I can not find it. The High pressure hose has 2 caps.

As weird as it seems, you're right. I just checked my 00Silvy and it's the same setup? Low and High ports on the same line.

After reading this again today I had to run out and pop the hood on my 03. I could tell you everything about my 97 I used to have but I haven't hardly opened the hood on this one. The two fittings are on the same line but there is a junction in between them and what looks like a pinch in the line down from the low pressure fitting. That pinch is what holds the orifice tube which seperates low from high sides.

The two fittings are on the same line but there is a junction in between them and what looks like a pinch in the line down from the low pressure fitting. That pinch is what holds the orifice tube which seperates low from high sides.
This makes sence, Ill work 0on it tomorrow thanx

This makes sence, Ill work 0on it tomorrow thanx

Pitch that wal mart death kit.

You need a recharge gauge set with the low and high side gauges to recharge and or check the system.



With compressor jumped and running post back you low and high side readings at idle and at 2K.

With a ac recharging gauge set.
Like one of these.http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets


http://www.ackits.com/merchant.mvc?S...ory_Co de=DIY

Low side should be close to 30 lbs.
If it is dropping under 25 lbs the switch will cycle or shut off compressor.

Wal Mart DEATH KITS

You cannot properly and safely recharge an air condition system with them.

The one side stop and go gauge does not tell you what your system is doing or is over charged or undercharged.
A overcharged or malfunction air condition system can reach over 500 lbs of pressure.
Enough to blow up that can or system and freeze you at first and the burn you or blind you and if any propane /butane in there blow and light you up.

The stop leak crap and who knows what kind of oil in the kits there will stop your system for sure.
Just like pouring super glue in it.
And some kits even contain freon with a butane mixer.
Good for a big blast.

If you are going to do it do it right and safe.
Here is what you need to start with.
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

In the older days you could just throw in a can and go.
But over the years just adding freon is getting harder to do.
Newer systems have to have the correct amount of freon down to the ounces.
Most will need pumped down and vacuumed down and the right and amount of oil and a set amount freon charge installed to get the air to cool right and the system to last.
If an air condition is low there is usually a leak that needs fixed and also a lose of lubricating oil from system.
Also air and moisture enters a low system
If you are going to try to do it get the proper type air condition gauge set with the low and high side gauges.
Hook up the gauges and get a reading with compressor running at idle and at 2000 rpm on the high and low side.
Post back pressure reading and we can help you.
MT

Hey There, I hope you are having luck on your AC. I am a licensed AC tech in south texas, and I sympathize with you :)

I tried reading my silverado's ac pressure and was stumped. The design is such that, the pressure is dropped across the orifice tube. It acts like the expansion valve in older systems. I finally figured that out after scratching my head and swearing there is NO low side hose.

You definitely should flush, vacuum, and recharge that truck before things get worse. You are going to be shocked what you find on that orifice!! It is a filter that lies between those two fitting you found on the one hose (low and high side).


Good luck and let me know if you need any step by step on how to flush, vacuum, or recharge the system. I am a big fan of DIY. I use an old refrigerator motor to vacuum out all my systems and it has been working great for 5 years. I have fixed many a system with it.

Good Luck!

How often should the cmpressor cycle on and off. Is this a sign of low charge if it cycles

If it is cycling on and off at idle, like on for 3 seconds, off for 5 seconds, yes this is a sign of low charge.

You can bypass the pressure switch at the dryer but I wouldnt recommend it. You should have it serviced. When a system is low on freon, it is also low on oil. This can cause your compressor to go out.

How often should the cmpressor cycle on and off. Is this a sign of low charge if it cycles


Yes and no.
High side pressure to high and bad pressure switches and orfice tubes and over heated condensers and evaporator core problems can also cause cycling.

With compressor jumped and running post back you low and high side readings at idle and at 2K.

With a ac recharging gauge set.
Like one of these.
http://www.ackits.com/merchant.mvc?Screen=CTGY&Store_Code=01&Category_Code=RefrigerantGaugeSets

http://www.ackits.com/merchant.mvc?S...ory_Co de=DIY

Low side should be close to 30 lbs.
If it is dropping under 25 lbs the switch will cycle or shut off compressor.

How often should the compressor cycle on and off when engine is idling or is this a sign of low charge. What should the hi side be at idle and at 2k rpms?

How often should the compressor cycle on and off when engine is idling or is this a sign of low charge.
answer when ever it pressure drops down around 25 lbs.
is this a sign of low charge"?
Answer yes and no.

Give us your low and high side readings for more help.
MT

High side depends on the charge in system and the ambant temp and the air going threw the condenser.
200 -250 is good high side pressure.

Thanks for everybody's help and info. I will let you know what the outcome is once I get the gauges.

Well, I ended up taking it in and found that the A/C Compressor is locked up and needs a new drier/acculator. $1000

I have another question. I do not feel like spending $500 on a new compressor, but I will if I have to. What is the best brand of Compressor and do you think a Remanufactured will be ok? Most of the ones I am finding come with a 3 month warrenty.

I have had good luck with both NAPA and All Seasons rebuilts.

Is the Drier the samething as the Accumulator?

Yes. If your doing it yourself make sure to get new gaskets, seals and O-rings.

You have two ac fittings. Of the two pipes, the LARGE pipe is the LOW pressure, the SMALL pipe is the HIGH pressure! Do not force freon on the hight side or you can say bye bye to your compressor.

If your AC quit working, try tapping on the low pressure switch with the back of a screw driver or something. The low pressure switch can stick sometimes espically if the ac hasnt been run much. The low pressure switch is the little ele switch in the side of the receiver drier.

Well, I ended up taking it in and found that the A/C Compressor is locked up and needs a new drier/acculator. $1000

I have another question. I do not feel like spending $500 on a new compressor, but I will if I have to. What is the best brand of Compressor and do you think a Remanufactured will be ok? Most of the ones I am finding come with a 3 month warrenty.

3 mo. warranty is not much.:grinyes:
4 season and murry rebuilts are junk.
If you are going to do it go a new compressor.
Check local parts places on new compressot prices.
Also ACkits.com

Thanks for the heads up MT