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High pressure reading same as low pressure side

azvette on Thu October 25, 2007 10:55 AM User is offline

Year: 2003
Make: Chrysler
Model: PT Cruiser
Engine Size: 2.4 Turb
Ambient Temp: 90
Pressure Low: 30
Pressure High: 30

Started the car yesterday afternoon and the A/C would not produce cold air. Put the gauges on, and when the compressor engages, both the low and high side drop to 30 and stay there. Any suggestions?

mk378 on Thu October 25, 2007 11:47 AM User is offline

You're not measuring properly. I think some of the PT's had a last minute "redesign" leading to the inculsion of an extra "high" port which was actually on the low side, just for confusion.

Also of course, be sure the valve wheels on your manifold are CLOSED while measuring the operating pressures.

2POINTautO on Thu October 25, 2007 5:32 PM User is offlineView users profile

For your learning process, look around the entire system so you can understand about the low pressure hose and the high pressure line. Some Volvos and others, do not even have a low pressure fitting for the DIYer to top the system off.

I wonder why they put a high pressure fitting on the low side, to service faster at the factory from 2 high pressure feed hoses.

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Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

azvette on Thu October 25, 2007 5:38 PM User is offline

Thanks for the tip!

After a little searching I found TSB 24-010-02, which addresses this:

24-010-02 04/01/2003 A/C , except turbo model -
There are two ports on the A/C lines near the accumulator. The port in the liquid line on top of the shock tower is for factory use only and should NOT be used for measuring compressor discharge pressure. Use the port located near the compressor.

I was using the port on the shock tower, so this seems like it could be the cause of the identical high side readings (even though I am working on a turbo model). I'll check it out later today and reply with what I find.

azvette on Thu October 25, 2007 5:45 PM User is offline

Quote
Originally posted by: 2POINTautO
For your learning process, look around the entire system....

A good suggestion, no doubt.... but it's amazing what you can't see inside this engine compartment. There are probably worse cars out there, but this thing has to be a mechanics' nightmare.

azvette on Thu October 25, 2007 9:05 PM User is offline

Okay, I put the car on stands and removed the right front inner fender well (which is the only way you can see 90% of the compressor). I took about 20 minutes looking everything over. I followed every A/C line for its entire length. I inspected every side of the compressor I could with an inspection mirror and felt by hand. There are a few places on the compressor that cannot be seen or touched. I could not find any other ports in the system. At this point, if there is a third port in there somewhere, I really doubt I could get a connector on it.

Any other ideas? I'm open to any suggestions.

Chick on Thu October 25, 2007 9:39 PM User is offlineView users profile

What was the staic pressure and the outside temp taken at...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

azvette on Thu October 25, 2007 10:07 PM User is offline

90 degrees
around 70psi. (I didn't record the exact reading, it but that's what the pressures were returning to when the clutch disengaged.)

Chick on Thu October 25, 2007 10:10 PM User is offlineView users profile

Ok, have the system refrigerant recovered, then recharge into a deep vacuum the amount on the underhood sticker, cooling should return and pressures will fall in line....I believe the system is just about empty.. Charge liquid into the vacuum until it won't take any more, then start the AC and finish off with gas until you get the exact amount in..

I am at home and can't seem to find which compressor it uses.. Almost like Chrysler is keeping it a secret. But the static pressure should be around the same as the ambient temp around it, in other words 100 degrees under the hood, static should be around 100psi..Your system appears to have just gas left..."If" it uses a Variable displacement compressor it is even more likely to be empty..

DO NOT charge liquid with the AC running thru the high side of course...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

Edited: Thu October 25, 2007 at 10:17 PM by Chick

2POINTautO on Sat October 27, 2007 1:22 AM User is offlineView users profile

OK, how are you going to vacuum it out, do you have any AC equipment, the internal system is not air tight, meaning, the LO side and the HI side are really connected with a restriction, not any type of blockage.

Vacuuming out the suction line will get the job done. Vacuum pump, a manifold gauge set and one can of freon hooked up but no hole pocked in it yet. The LO or HI pressure hose can be put on the pump and the other hose can be hooked up the the suction line of the car, arent you lucky you have a choice. Suck it dry, leak check it, pop the hole in the freon can to let it suck into the system, start the car, turn on AC, put the rest of the can in a bucket of hot water to allow the gas to enter the system.

When you change cans, be sure to bleed out some gas from the car while screwing the can onto the service hose to bleed out the air from the hoses. Keep the top of the can upwards so liquid does not flow into the car.

More help here if needed and instructions too. In My Opinion, if you get this done at a shop with a recycle machine and they hood up both hoses to the suction line and reservice all that liquid to the suction line, I would let it sit for some time before turning on the AC to allow the liquid to go back to gas and equalize throughout the entire system. I think this would be fine and ask them if you can check it out the next day even, I would not take any chances on hydro locking the compressor.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

azvette on Mon October 29, 2007 3:09 PM User is offline

Thanks for all the help.

I traced some oil residue to a couple of pin hole leaks in the suction line. Everything else looked clean. I just picked up a new line, and I'll swap it in and add a couple of ounces of oil (and maybe some dye?). Then I'll vacuum it out and check for leaks.

bohica2xo on Mon October 29, 2007 4:27 PM User is offline

AZ:

Dye is always a good idea. The OEM's use it to reduce diagnostic time at the dealer level - if they spent the extra 40 cents, you should too.

Ignore that convoluted mess posted above. If you want to evacuate the charging hose (a good thing to do), convert your manifold to 4 ports - here is the link:

How to convert your manifold to 4 ports

On a TXV system like this you should avoid dumping liquid into the suction side. Doing that will rinse all of the oil from the compressor as it blows past the reed valves to equalize the system. Liquid should be added to the high side on a cold system with the engine stopped. Add as much of the charge as you can before closing the high side valve & starting the system. This is to make sure you have enough refrigerant to return some oil to the compressor while you complete charging.

Once you have a full charge, test the system at 2,000 engine RPM, cabin fan on highest speed, both doors open.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

azvette on Thu November 01, 2007 8:24 PM User is offline

Okay, here's where it's at.

I replaced the suction hose and added 2 oz of oil and 1/4 ounce of dye. I then vacuumed out the system for 30 minutes three times, waiting about 7 to 8 hours between each time.

With the car not running, I slowly added liquid r134a to the high side. The system took about 9 oz this way. Then, with the car and A/C on, I added the balance of the 18oz the sticker calls for. I used a digital scale to measure the weight.

The temp was around 87 in the shop.
At idle the low side was 33 psi, the high side 42 psi.
At 2000rpm, the low side was 24 psi, the high side 40 psi.
Static pressure was 52 psi.

The air was blowing cold(er).
Doors open, max fan, outside vent: 57 degrees
Doors open, max fan, recirculating vent: 47 degrees
Doors/windows closed, max fan, recirculating vent: 41 degrees

So, I still don't know what's going with the pressures, but the air is now working to some extent. Any comments?

Again, thanks for all the help here. I would not feel confident in attempting these types of repairs without this forum as a resource. I really appreciate everyone sharing their hard-earned knowledge and experience here.

Chick on Thu November 01, 2007 8:50 PM User is offlineView users profile

Are you sure your guages are working? are they good ones, or HF type?? You're getting cooling, and the pressures don't indicate it... Are you depressing the high side shrader valve, try pushing it down to fully open it..

-------------------------
Chick
Email: Chick

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Freedoms just another word for nothing left to lose

2POINTautO on Fri November 02, 2007 2:15 AM User is offlineView users profile

Try your gauges on another car and back to yours again, connection issue here.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

bohica2xo on Fri November 02, 2007 11:32 AM User is offline

Well, the good news is that your system is working.

Your pressure measurements are not at all in line with the system performance however. One or more of your measuring tools is not working properly.

First, you state a static pressure of 52 psi. This is about half of what it should be with a full system

Second, your high side pressures appear to be impossibly low for the vent performance listed.

Let's go through the basics:
Both manifold valves must be closed for testing
Any manual shutoff valves at the service connectors must be open.
With both hoses connected, you should show pressure on both gauges, and no refrigerant should leak from the center port of the manifold.

Assuming the manifold is in good shape, and used properly, the next suspect is the high side connector. Some combinations of port+conector have too much tolerance, and the schrader valve is not depressed. When you first install the connector, it travels farther & depresses the valve briefly. You get a static reading of the pressure stored in your hose.
Try squeezing the high side connector onto the test port as if you were installing it. If the high side shows a different reading, you have found the problem. Use a cable tie or hose clamp wrapped around the tube & connector to pull them together firmly while you test.

If the high side connection is working properly, then the calibration of the high side gauge is suspect. If you can borrow a manifold set, compare a second reading to yours on the same vehicle. Gauges can be tested / repaired / calibrated - but it is usually cheaper to just replace a faulty gauge.

Other items that may be affecting your readings would include an out of calibration thermometer or scale.

You can calibrate a stick type thermometer by using a thermos full of crushed ice & water. Put most of the probe in the water for 5 minutes. Read the scale while still in the water. If it does not read 32f, it can be adjusted. Use a small wrench on the back of the head - there is a hex there. Grasp the outer edge of the head, and twist it gently against the hex to align the needle with the proper temperature. If you have removed the thermometer from the ice bath for adjustment, re-check the calibration again after adjusting.


B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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