Slow to Cool - High Side 'Too High' 2010 Chevrolet

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Slow to Cool - High Side 'Too High' 2010 Chevrolet

Postby pgtr » Sat Aug 12, 2017 9:03 pm

Have a 2010 Chevrolet Corvette automatic w/ standard LS3 motor.

Last summer the car would occasionally take 1-2 minutes to start cooling.

This summer in the afternoons it is taking up to 5-7 minutes before it starts cooling. The RH side vents will show signs of cool air about 30 seconds before the LH vents. This issue ONLY occurs after the vehicle has sat for an extended period of time in the sun - about 3-4 hours in the afternoon. If the car sits for say 1 or 2 hours - no problem. No variation in the HVAC head unit settings seems to have any affect on the issue, auto/manual, recirc, dual mode on/off, cyclcing the on/off, etc...

Once it starts cooling - it is VERY cold. Going home in the afternoon on a 105F, outlet temps can hit 40 or even lower.

Since I only have a shot once a week on a Saturday or Sunday afternoons at troubleshooting - I really haven't made much progress. Here's what I've observed.

When it occurs the compressor IS engaged but the cool line is not cold to the touch - it remains relatively warm/hot from high ambient temps. At about 5 minutes the low side line gets cool to the touch. Same time the air starts cooling at the vents. This tells me there's probably nothing wrong w/ the air blending box.

I haven't had a chance to duplicate the issue w/ gages but here's what the gauges say when it is cooling at about 100F 50% humidity. Low side: 50PSI; Hi Side: starts at 275 can climb as high as 350 or sometimes higher - approaching 400ish when it's real hot and idling a while. Hi side seems way too high.

Service history: Under warranty dealer treated for 'smelly socks' odor and replaced the HVAC head unit - that was in 2012 when it was 2 years old. Nothing since then and no indication of refrigerant work.

Other than the miserable first 5 minutes driving home in the afternoons in 105F - it really blows cold. But that 5 minutes lasts an eternity w/ a black interior and a 130-140F interior temp. And I'm bothered by what seems to be a rather high pressure on the high side.

Overcharge? (which seems strange given it appears to be a factory charge from 7 yrs ago), Blockagage? ...

I'm going to try and duplicate it again and this time study the gauges while it's not cooling. My concern w/ taking it to a shop is that they'll not be able to readily duplicate the 'slow to cool' issue because it can only be duplicated once a day. They can of course see the high pressure reading any time.
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Re: Slow to Cool - High Side 'Too High' 2010 Chevrolet

Postby bohica2xo » Sun Aug 13, 2017 9:16 am

Recover & weigh the refrigerant.

If it is out of spec, then recharge with proper weight & re-test.

If it is within spec (unlikely after 7 years) pull the filter & inspect it.
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Re: Slow to Cool - High Side 'Too High' 2010 Chevrolet

Postby pgtr » Sun Aug 13, 2017 12:02 pm

Vehicle sat overnight in climate controlled GA. Rolled the car out of the GA, hooked up the gauges. outside ambient temp about 98 (still a little early - no triple digits yet)

Statically w/o engine running the low side: 75; high side 125.

Turned it on and here's what I observed. AC ON, Fan HIGH, AUTO OFF, Recirc ON, RH window down (so I could reach in and feel air temp, read thermostat...)

As usual, there was NO cooling for first five minutes.... compressor remained engaged and spinning whole time no cycling...

Lo side move slowly up and down between approx 65 and 75 (compressor was NOT cycling - just running), Hi side went up to about 150 and kinda sat there....

This continued for about 4 initial minutes... (there was perhaps a very very slight increase on the high side during this time...)

Several things tarted happening at about 4 minutes....

The high side started creeping up steadily albeit slowly... an electric fan could be heard to start spinning up front (can't see much on this car)... the low side stopped moving back and forth and stabilized at about 65...

Then in few seconds later cool air could be felt inside at the RH vent and the lo line was felt to be cold to touch.

From this point on - the inside temp were getting pretty cold - probably in the 50s. From the occupants perspective the AC is working after the usual 5 minute delay. The Lo side slowly but steadily dropped to 45 or so. The high side kept on climbing and climbing (the cooling fan (or fans?) is fully roaring by now) 275, 300, 350, 400 stabilizing at a bit north of 400 after 10 or 15 minutes (by then the low side had crept up to maybe 48 or so).

Car does not run hot at cruise or while idling. Can't see any blockage or debris on the condenser coils/radiator.

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Re: Slow to Cool - High Side 'Too High' 2010 Chevrolet

Postby pgtr » Mon Aug 14, 2017 7:47 pm

One final work-around I've discovered - which unfortunately mostly muddies the waters and confuses me...

In the afternoon when I'm facing a 140F interior temp and at least 5 minutes of heat... if I start up the car, pop the hood and, w/ the AC compressor running, simply unplug and reconnect the pressure switch - it causes the compressor to of course briefly cycle off and on once... But when I get back in - I'm only seconds away from cool air - NOT the usual 5+ minute wait sweating away!

Cycling the A/C switch on the HVAC H/U on and off, while it does cycle the compressor - does NOT have the same affect!

Further - I've been thinking that I have a purely mechanical or physical problem w/ the refrigerant, blockage, contamination. Maybe I'm dealing w/ more than 1 issue here.

Anyway the solution does get the coolant to start flowing and cooling almost immediately w/o waiting the eternal 5+ minutes - but obviously I don't want to have to do this trick ever time. It's still a bit slow. And of course there's the high pressures on the hi side.

Finally - I'll add that in re-reviewing the service records - there is also a record of the dealership installing a product called 'Frig Quiet' when they replaced the HVAC head unit and treated the odor back in 2012.

Also does anyone know what the factory spec is for how much refrigerant is to be installed in a 2010 Chevrolet Corvette?

Thanks for any feedback and suggestions on this strange behaving A/C!

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