Automotive Air Conditioning Information Forum

Hose pinch test.

Pinched both hoses as I don’t know which one is feed or return. No change.

Did test in garage, at 2k rpm, and vent temps the same as previous 2000 rpm test. There is no “center” vent. There are 4 vents spaced evenly across the dash. I was using the left of center vent near driver for temp measurements. I placed a second digital probe, in the right of center vent and that vent read 2 degrees colder.

I have yet to take the car to work (airport) which is about a 40 minute drive down 17 and then 10, which is a good test for 70+ mph speeds and consistent running and a chance to pull heat out of the car.

As an aside, the pulley on the Denso unit (new) is smaller then the pulley of the old unit, not much, but a front to front eyeball showed a difference. The crank pulley is larger then the Ac pulley, so looks like the GM engineers took into account the low rpm nature of the engine and made the compressor over driven.

I appreciate all the help and hope this thread contributed to the forum.

Do you recall or can you look up which OT you installed? The plastic part should have been all white in color with a single black o-ring and a 0.072" orifice. It's OEM part number 15-5151.

This is the O/T

https://www.amazon.com/gp/product/B00SL ... UTF8&psc=1

The part I received was all white, and identical in all regards as the OEM one I removed.

The link points to an OT that is the variable type, which have been troublesome and in some cases, don't work at all. The one you said you actually received sounds correct, though. I only wish we knew what the orifice size is. That's the most important part. A smaller orifice than the stock 0.072" would let less refrigerant through, and vice-versa.

That's one of the cheapest quality VOT around, and why it's 7:00 dollars.

I bought that two years ago, I wonder if they changed the item?

Did my drive to work test, OAT 108, 25 min I-17 at 70mph, blower on high, recirc on. Vent 47.8* Actually turned it down when I got to I-10, was getting chilly!

The actual vent temperature should drop a bit more with a lower blower speed because the air flowing across the evaporator has more "dwell time" to cool off. In other words, the air stays on the evaporator coils slightly longer with a lower velocity.

Are you satisfied with its cooling performance now, or would you rather try another OT? I'd probably replace the OT again. But I wouldn't blame you if you opt to leave it alone since you've done so much work on it lately, and it's cooling pretty good now.

I’m good with it for now. If I have cause to discharge the system, I’ll pull the OT. I’m going to order the part number listed here to have on hand.

Sounds like a good plan. When October rolls around and the average daytime temperatures in your area drop into the "cooler" 90°F range ( ), you'll be able to run the system in a more reasonable environment to see how it does.

Just posting a follow up for posterity.

Had a cooling fan issue (fans on high all the time) and the scanner live data showed a AC PRESSURE - HIGH. (Key in, engine off, AC not run). After several days of having the fuse for the fans pulled I took the car to a mechanic with a GM TECH2 scanner. Put the fuse in and fans operated normally. But, the mechanic noticed the AC PRESSURE - NORMAL. So, we both agreed it’s a faulty AC pressure switch, which commands high/low fan speeds based on high side pressure.

Also, this car has the dual climate zone. The passenger side actuator was found to be not moving the blend door to the full cold position consistently. This may have been the cause of me chasing inconsistent vent temps. New actuator installed and the blend door moves full range.

Lastly, until this episode with fans on high constantly, I had never heard the fans on high at any time with this car. In Phoenix with the AC on at idle, I would assume the fans would have been on high at some point.

I’m going to replace the pressure switch. I think it’s failure mode in sending the high signal is as inconsistent as it never before sending a high signal .