AC hi on low pressure side no cooling

[AZyeaha]

AC hi on low pressure side no cooling-fixed

I have a 2000 beetle tdi. The ac suddenly was blowing warm. Checked with gauges low side running at 60 -70 hi side normal 200-225. switched out expansion valve got same readings. Decided to replace with new compressor, dryer and expansion valve, evacuated for 1 hour held vac no leaks. Charged system was getting close to normal readings cool air, next day back to hi pressure on low side warm air?? I had blown out all the lines, drained the new compressor of oil, distributed the required amount of oil between compressor dryer and evaporator. Turned the compressor by hand many turns before charging, also after first can of 134 turned by hand before startup, then charged. I have now noticed the fans do not come on with ac. Compressor engages still hi pressure on low. Jumped the fans to stay on while running with compressor engaged still same readings. I will have to replace the fans, power is getting to them as volt meter tested, direct current to fans only run on hi low terminal direct current no run. I'm I missing something here or could my internal Refridgerant Control Valve be bad in by new compressor?? Meanwhile I will work on the fan issue and double check the condenser is clean and not blocked by debris. AC reading were made in Arizona heat around 100-105 deg. at several times. I have done many compressor and recharge/repairs projects on other model cars, no problems Thanks for any insight to this issue

 

[AZyeaha]

replaced cooling fans

Replaced cooling fans they work great, still same compressor engaged no cold air.

 

[wmgeorge]

And how did you charge the system by weight or ?

Thought for the day, are you in the re- circulating mode or bringing in outside air, on our Beetles the compressor holds the low side at 18 - 22 lbs and the temperature control just dumps hot air from the heater core to warm it up if your too cold.

 

[AZyeaha]

charged

I charged with 2, 12 oz cans @ 340 grams each. System sticker notes 700 grams +50. Blew out as much oil as possable all lines, condenser and evaporator before putting 4 oz back in, new dryer as well. I don't believe I over charged it. re-circulating mode.

 

[DIESEL DAZZLER]

Ac

Check the heater control lever under the heater box above the tunnel.The lever pops off the mix door .Can reached from pass side by moving center consule back.The lever fits one way,so you might have to line it up and push it back on.

 

[wmgeorge]

I charged with 2, 12 oz cans @ 340 grams each. System sticker notes 700 grams +50. Blew out as much oil as possable all lines, condenser and evaporator before putting 4 oz back in, new dryer as welll. I don't believe I over charged it.

Sounds like your close enough. I'd check the re-circuculating mode some times the flaps stick. Or the temperature control that dumps the hot air from the heater core when you set the control warmer. If that was stuck or the cable came off and your in the not cool temperature setting.

 

[AZyeaha]

I do hear the flaps move when the controls knobs are turned. I will double check the connections. Will a stuck mix door really make the low side pressure high? I get the reading as soon as the car is started and not even warmed up. I'm not sure how much 134 is in the system right now as I was bleeding some off in case of overcharge. I could empty evacuate and start over. But I'm not sure anything would be different.

On my 97 Jetta it did the same thing. Replaced the compressor, dryer, expansion valve. Lasted about 2 years. Then same numbers as Beetle I'm working on now. However I came across an article explaining how the refrigerant Control Valve is finicky and can be replaced with a bolt. This makes the variable stroke compressor to a standard one. I did it and had satisfactory results as an experiment. Down side, evaporator may freeze up, but in Phoenix not as likely. I can send the article pdf if anyone if they would like it. One note bolt size 13mmx26mm fine thread not 7/16 as mentioned in article.

I'm not ready to do that to the Beetle as that compressor is 1 week old and under warranty.

 

[wmgeorge]

Well since only a few things can cause high low side pressures. A high heat load on the evaporator would be one, but that would also tend to increase the high side pressure. If your expansion valve was overfeeding the suction side would be higher than normal and the line coming back to the compressor would be cold.

My best guess not actually seeing the system would be whatever is controlling the pressure inside the compressor, as controlling the variable displacement is either bad or needs adjusted. That is after you have ruled out the recirculating door position and other issues above.

 

[AZyeaha]

I'm going to check the mix doors. I popped the back cover of the original compressor off to inspect, it is very clean no particles what so ever. This was just to rule out as much as possable debris in the system. I think it is a Refridgerant Control Valve failure. I could probably put one in the old compressor they are about $50. It will probably take some time to see if I can warranty the new compressor, put the old one back in so at least the car can be driven. I'll update as I go. Thanks

 

[Ski in NC]

If heater flap is culprit, when you first start car with engine cold, it should blow cold until engine heats up.

 

[AZyeaha]

Read a few older threads a few had the exact symptoms hi low side at 70. They replaced the compressor or RCV refigerant control valve. AC compressor company will warranty the compressor I have now, sending another to me. I'm 99 percent sure its the RCV. Discharge, vac and fill again. Online AC supply Co. Polar Bear has them for $30. I may gamble and get one for my original Beetle compressor as the internal is very clean and my Jetta could use it.

 

[wmgeorge]

Read a few older threads a few had the exact symptoms hi low side at 70. They replaced the compressor or RCV refigerant control valve. AC compressor company will warranty the compressor I have now, sending another to me. I'm 99 percent sure its the RCV. Discharge, vac and fill again. Online AC supply Co. Polar Bear has them for $30. I may gamble and get one for my original Beetle compressor as the internal is very clean and my Jetta could use it.

Makes sense to me. I am not sure how they are doing the control. On the big commercial units there are a several ways. Some read suction pressure by a diaphragm of some kind and either disable the suction reeds or bypass internally hot gas over to the suction side. Some have an external valve that is controlled electronically to adjust the loading and unloading of the compressor.

It looks like the SANDEN is reading suction pressure and using a pin to either bypass hot gas over or disable a suction reed.

 

[KLXD]

I thought they were variable displacement. I have my old one to dissect some day.

 

[AZyeaha]

You can susbtitute a 13mm x 1" fine thread bolt and nut for the RCV. You will have to monitor the evap temps when you do this as it may freeze the evap.
Look at http://www.aircondition.com/tech/que...-Control-Valve valve and reeds in right pic.

Download the PDF and it has the article.

this has the compressor diagram http://www.ackits.com/diagrams/Sanden2.pdf

 

[Genesis]

The Sanden compressors are variable-displacement; I would not substitute a bolt but rather would fix the bad valve.

 

[wmgeorge]

I'd like to have one just to tear apart.

I used my repaired AC yesterday for the first time on the road and 95 degree day. This is after replacing the clutch coil. It was over charged and cycling on the HP switch, a little charge adjustment and it seems fine.

 

[AZyeaha]

Well switched out compressor with another new one, supplier replaced, deep Vac'ed out, charged, Blowing 32-34 deg on 108 deg day. Pressures are 18-25 lo 190-210 hi. On another note when replacing compressors if the manufacture says the compressor is oil charged, be sure to drain and measure that amount from compressor. I had specifficlly asked if the oil charge was the full amount needed they replyed I would have to add a couple oz. This may have contributed to hi, lo pressure.
Completly drained replacement compressor 4.5 oz came out that is a full oil charge. Or just a faulty unit to start with.