1999 T5M56 poor AC performance 20 F delta (OHIO issue - overcharged it)

Post by **abscate** » 07 Sep 2018, 04:11

I’ve lost performance since I replaced my compressor replacement in January 2018 . aC performance I mean.

I had a good35-40F delta at1500 rpm, now only getting20

Charge showing45 psi low side, 80F ambient, compressor on full time.

I’ll check cabin temp sensor?

Possible plugged orfice tube?

Possible blend door leak/ issue

Getting good sweating all the way to drier from firewall.

Post by **scot850** » 07 Sep 2018, 06:22

Check your cabin temp sensor is not plugged or faulty. No matter what you set the temp to if it is not working correctly then it doesn't matter what you set your temp to it will not sense correctly.

If you need another and can wait a week until I get back to Calgary I can pop one in the post to you.

Neil.

Post by **jimmy57** » 07 Sep 2018, 07:52

If it is cabin temp sensor then turning temp knobs to full cold will override and close blend doors to stop any heated air mixing.
If it has run for a few minutes and it is 80F ambient then 45 is too high for low side pressure. That could be as simple as overcharged or the new compressor is not pumping well. If you let refrigerant out and it improves you have your answer.
This is a time that no high side service port hurts.

Post by **abscate** » 07 Sep 2018, 09:57

jimmy - I can monitor high side from the OBD port via the high pressure switch, can't I? Is that reading reliable enough to troubleshoot AC?

Post by **abscate** » 07 Sep 2018, 11:53

Well, now my manifold gauges arent reading any pressure - but the system is sweating nicely....diagnosis - plugged gauges.

See why you never use sealer??

I got the pressure down to 32 and now am at 35F delta. Its still slightly overcharged, I think

Post by **jimmy57** » 07 Sep 2018, 12:04

Yes, if you have Vida or other scan tool. If you disconnect the a/c HPS the ECM will shut off compressor and it can't run fan properly.

If you turn fan to slowest speed, recirc selected, doors and windows closed, and run engine at 1200 or more and it doesn't come down to low 20's and cycle compressor in 4-5 min or less then it is very likely overcharged. If cooling fan comes on then you know it exceeded 190 psi and that speaks to compressor being healthy. If it turns fan on high then the high pressure is going over 260 and that is damning for overcharge. Not going to high fan with ambient in 80's is not indicative of it NOT being overcharged as 80's is cool enough to not push excessive high pressure with 4 to 8 ounce overcharge that could push low side to 45 psi.
I use the compressor cycling check on CCOT systems as aftermarket condensers and other parts can change the correct capacity a couple of ounces in some cases.

Post by **jimmy57** » 07 Sep 2018, 12:07

With the system set as described above it should go to low enough to cycle off and do a 40-60 second cycle. If the fan speed is increased then the low side will go to the 30's and not cycle. If it is a little overcharged it will cool great but low side will not drop to low enough pressure for switch to open compressor circuit and it will freeze after extended use especially after dark.

Post by **abscate** » 07 Sep 2018, 13:05

okay - idiot disclosure

I had 35F after recharging with just two cans, 680g Full charge is 750g per sticker, and I like to be on the high side for cold climate.

I thought I metered an extra 100g by weight into the system, which is when I lost the good Delta-T

Am I am idiot for trying to charge to spec instead of performance - which would have said "LITFA"

I was a little worried that, being in the low side, I was in the dangerous area of enough charge for good AC but not enough to circulate PAG.

Is that’s more of an issue for TXV systems than orfice systems?

Post by **jimmy57** » 08 Sep 2018, 08:51

The charge has to be very low, something below 50% before lubricant circulation is compromised. Too much and you have liquid going into return (suction) of compressor and hydraulic non-compressability and lubricant displacement becomes an issue.

TXV can have the issues of throttling too much and compromising lube. The use of temp probes "fixes" that. Of course a temp probe on a TXV system makes it sort of a hybrid since you now cycle the clutch as with CCOT.
Variable displacement compressor with TXV has been THE answer used widely. P2 XC90 with V8 or 3.2 I6 and all P3 and new models. You spec a slightly higher capacity giving you all you need for idle speed/hot weather and then you dial down displacement to keep a narrow temperature band and no clutch cycling and no freezing.

Charging by spec is the best way but I always verify on CCOT as these have more sensitivity to charge.

Post by **abscate** » 08 Sep 2018, 13:45

Thanks for sharing the Five rivers of information, Jimmy