AC overhaul - Compressor upgrade? Condensor?

[L31MaxExpress]

I have the factory coolant diverter valve that seem to be working. My issue comes in specifically at speed. 2krpm in the city is around 4* C colder than 2k rpm on the highway. I get instant couple of degrees of temp drop idling slowing down to less than 45mph off the highway exit.

Sounds like the cycling switch may be cutting out too early. I have seen numerous examples of the stock switch start cutting out the compressor as early as 60 psi and cooling drastically suffers. Change the switch and the systems will go right back to cooling correctly. I carried a spare stock switch in the glovebox of my Express van for years as it failed more than once. Then I found the R134a thread older style adjustable switch. That switch is still living over 10 years later. I would fit it with an adjustable switch myself and dial it in to cutout just before the evaporator core freezes into a solid block of ice. I checked the 87 G20 van the other day and the cycling switch is cutting the compressor at 18 psi on it. 18 psi is equivalent to the refrigerant boiling at 25F. R134a would need to cutout at 21 psi in theory. R152a has nearly 2x the latent heat of evaporation of R134a requiring substantially less refrigerant to do the same work in the evaporator core.

Four Seasons 36496 is the R134a thread adjustable switch and it is calibrated at 22 psi out of the box. OE application includes a 1994 G10/20/30 van. 37219 is the connector replacement for that switch.

 

[PlayingWithTBI]

Four Seasons 36496 is the R134a thread adjustable switch and it is calibrated at 22 psi out of the box

Will that one work with an upgraded R12 system like, in an 88?

 

[L31MaxExpress]

Will that one work with an upgraded R12 system like, in an 88?

No but 36674 will. It has the 7/16 thread vs the metric thread on the prior part number. Spec sheet shows the 36674 as a R134a retrofit switch for a R12 system and it is claimed to have a 21 psi cutout out of the box. The connector is the same for both. The 87 G20 has a UAC switch equivalent to the 36674 on it. Took about 1/2 turn CCW adjustment to cut out where it does now.

 

[L31MaxExpress]

Will that one work with an upgraded R12 system like, in an 88?

This is right before the cycling switch cuts the party in my 87 G20 with the engine at 2,000 rpm. It has been very humid here in the aftermath of the recent hurricane and the evaporator core has not frozen enough to reduce the airflow in any driving condition. Going down the road or at 2,000 rpm, after 2-3 minutes, the compressor cuts out briefly and any ice built up thaws off quickly and it is back to cooling cold again in ~20-30 seconds. The air blows about 10F warmer when the compressor cycles off so I can tell the cycling switch is doing its job.

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[PlayingWithTBI]

No but 36674 will. It has the 7/16 thread vs the metric thread on the prior part number.

This guy? FWIU There's a valve behind the switch so you don't lose any of the charge, right?

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Edit, try this again...
www.amazon.com/Four-Seasons-36674-Mounted-Pressure/dp/B000CHETAS/ref=sr_1_1?crid=14N6DZNTFRZ4M&dib=eyJ2IjoiMSJ9._6eI8xnk3qy9pfPDHlHyRfjj1-P6xxbL7GU5Wei1OBnrZYrkJ5EApcO1NdNywUAGIt8Lugg4DHXlhsUCSc3aTQ7JycTCLRGsNVJ2KCxqPrgzHGgYUogUe7r-pKH8SlmbxpVjJ1D58CRpLXfijitKlqKdZ9--XWukmSjgNeBgIWmRXLDXW2H37R-B5H1ItBufcRCAJ7MUTaCTafXddnLenG39DRRMvVyL3w93RHpSnJ8.sOaHZShALVXTRCaj0qPf-CVyFNv7fdkxSEW1VsRqKKA&dib_tag=se&keywords=four+seasons+36674+switch&qid=1721247911&sprefix=four+seasons+36674+switc%2Caps%2C1302&sr=8-1

 

[L31MaxExpress]

This guy? FWIU There's a valve behind the switch so you don't lose any of the charge, right?

If the job was done correctly the fitting has a schrader core in it. Spin the switch off and it will release a small puff of refrigerant. Change the o'ring, put a little pag on it, spin the new one on and you will lose another small puff. Not enough refrigerant loss to even worry about. I am sure that little puff of refrigerant also purges the air out of the switch keeping it out of the system.

 

[L31MaxExpress]

This guy? FWIU There's a valve behind the switch so you don't lose any of the charge, right?

xc_hide_links_from_guests_guests_error_hide_media

Edit, try this again...
www.amazon.com/Four-Seasons-36674-Mounted-Pressure/dp/B000CHETAS/ref=sr_1_1?crid=14N6DZNTFRZ4M&dib=eyJ2IjoiMSJ9._6eI8xnk3qy9pfPDHlHyRfjj1-P6xxbL7GU5Wei1OBnrZYrkJ5EApcO1NdNywUAGIt8Lugg4DHXlhsUCSc3aTQ7JycTCLRGsNVJ2KCxqPrgzHGgYUogUe7r-pKH8SlmbxpVjJ1D58CRpLXfijitKlqKdZ9--XWukmSjgNeBgIWmRXLDXW2H37R-B5H1ItBufcRCAJ7MUTaCTafXddnLenG39DRRMvVyL3w93RHpSnJ8.sOaHZShALVXTRCaj0qPf-CVyFNv7fdkxSEW1VsRqKKA&dib_tag=se&keywords=four+seasons+36674+switch&qid=1721247911&sprefix=four+seasons+36674+switc%2Caps%2C1302&sr=8-1

That is the part number. The ones I have bought come with a plastic shipping cover protecting the protruding male terminals from getting bent. It slides off before install. I only mention that because somebody in a FB group could not figure that out a while back.

Here is the matching connector. It is not polarity sensitive. One wire goes to each wire off the stock connector.

Edit...I give up trying to get a link to the connector. 37219 Four Seasons.

 

[PlayingWithTBI]

Here is the matching connector. It is not polarity sensitive.

Hmmm we're having the same problem can you post it without the https:\\?

 

[L31MaxExpress]

Hmmm we're having the same problem can you post it without the https:\\?

www.amazon.com/Four-Seasons-37219-Harness-Connector/dp/B000E0QWDK/ref=mp_s_a_1_1?crid=3BWM63RPPA40V&dib=eyJ2IjoiMSJ9.kErizEI0FuzHDYhqaEwCRzVmPjWk2iJ4tA8PH8EE_hXKpcJA-Tr4z2upSAJPeuF0fU4WA8UJA0M62JNPkGhra9wCT2kQqqv46EuWock5kznrL2LTAINLEWVLMWM_mnZ2b4MS3OCiCK5M9FDDUHx0qjCPQLSlhOjXMRtWIT3BidvztJW_drtZi0DZH8r0Na2vCi-sAkKq-cmL2oRad-cBmg.m3EPlDwutv_5N1-eoDfQfDAssLEYFnrxF55SwK-ejzk&dib_tag=se&keywords=four+seasons+37219&qid=1721248592&sprefix=four+seasons+36674+switc%2Caps%2C1401&sr=8-1

 

[L31MaxExpress]

Hmmm we're having the same problem can you post it without the https:\\

What do you know that worked! ROFL.