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1990 GMC Suburban compressor and other parts...new question at bottom of post.

kd7kmp on Wed July 06, 2011 7:58 PM User is offline

Year: 1990
Make: GMC
Model: Suburban
Engine Size: 5.7
Refrigerant Type: R-12

Hey all,

I have a 1990 GMC Suburban that has completely lost it's charge of R-12. I believe the compressor is of the R4 variety which I understand is quite noisy whether new or not. Anyhoo...

A hole developed in the system and all the R-12 is now gone. The compressor was really noisy to begin with. I would rather convert the thing to R-134a than replace parts and continue with R-12. I have looked at a PFC for it, but I don't know what fittings to purchase to mate it to my existing lines (if someone has done this conversion with a PFC, please let me know). I plan on replacing the rear TXV, o-tube, o-rings, accumulator, condenser, compressor, etc, for the conversion. There are two things I'd like to know: 1--I've seen 6mm condenser that fits w/o modification which is supposed to be R-134a compatible. Does this unit have the correct fittings for the stock lines? 2--are there brands of compressors out there which provide better/less noisy R4 compressors than others?

It's not been too hot here in Utah, but I still want to have A/C that works reasonably well. I have all the necessary tools (gauges, vacuum pump etc) to install the parts and get it charged up. Thanks for the help.

Kevin

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I've already done a search!

Edited: Thu July 21, 2011 at 2:24 PM by kd7kmp

kd7kmp on Fri July 08, 2011 6:35 PM User is offline

Anyone have time to give some advice? Thanks.

Kevin

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I've already done a search!

TRB on Fri July 08, 2011 6:49 PM User is offlineView users profile

I don't know anyone that has adapter to convert your line to a PF condenser. 6mm is better than a T & F but still not as efficient as the MPMV condenser.

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JJM on Fri July 08, 2011 9:46 PM User is offline

If the system was simply leaking, why replace all those parts? Fix the leak, replace the accumulator, charge with R-12, and call it a day. It will probably be cheaper overall. A retrofit are rarely fun, and often does not yield the cooling of an original R-12 system without lots of modification - all of which costs money.

Every condenser out there is R-134a "compatible" but it doesn't mean it will perform well. You'll really need parallel flow condenser, which is going to involve fabricating hoses and fittings, not to mention adding a HPCO, R-134a service valves, smaller orifice for R-134a, XH7 or XH9 desiccant accumulator, readjust the CPS... and still you might end up banging your head against the wall.

Also after 20 years, all the hoses probably have to go, or you risk another leak...

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com



iceman2555 on Sat July 09, 2011 3:29 PM User is offlineView users profile

This vehicle should be quite easy to convert to 134a. The condenser utilized on this vehicle is most common in a PFHE model. A bit of research indicated several after market companies that produce this unit.
The issue with hoses...esp the rear units do represent an issue..however, it appears that this vehicle is going to stay in your 'stable'. A friend has one of these units and dearly loves it. It has over 300k and runs very nicely.
Back to the retro fit issue. If you desire to upgrade the system...not a retro fit...but a true upgrade....then look at new hoses for the rear unit. The Front manifold assembly is readily available and will utilize 134a type barrier hoses. The ADRD's offered today utilize the upgraded desiccants to function with 134a. Not sure if any one offers a 12 type desiccant today. Back in the mid to late 90's almost all ADRD mfger's had already converted to the 134a spec'd desiccants.

If the rear hoses are not available...or too expensive....these are easily made...a few fittings...some bulk hose.....a crimp job....and viola....new hose assembly. One could also consider that the rear unit is no longer needed...this too can be easily rectified.

This vehicle would be a great candidate for a upgrade...esp if one were to complete the upgrade in a straight forward manner. The use of a PFHE condenser will make the job much easier. The largest problem encountered with retro fitting was in the inefficiency of the R12 condenser to handle 134a. Utilizing the new condenser design will allow for a FULL recharge of 134a to R12 refrigerant...no more guesstamations concerning how much.....just charge the darn thing to OE spec's....and motivate down the high way.

The orifice tube should remain the standard GM unit...or perhaps..the CADDY replacement (yellow) but the standard GM unit will work great. Most all TXV are made for 134a and this should not present a problem for the rear unit.

The issue of the HPCO was a requirement from Uncle Sam...however, have seen many retro's that never had them...the R4 utilizes a PRV and this should be sufficient for operation of the system. The issue with HPCO was a result of an attempt to modify a system (r12) to allow the use of 134a and the higher operational pressures without having excessive venting. The PRV system is still utilized today and functions as it should. The new design condenser will aid in eliminating the excessive pressures normally associated with retro fitting. This does not fall under the retro fit banner....seems to me you simply wish to upgrade your existing system.....go for it....!!!

The noise issue with the R4 is always going to be there....it is the internal design of the unit that produces some of the noise. Have serviced this compressor for more years than I care to remember...some were noisy and some were not....the average noise issue is no normally more excessive than normal engine noises. If excessive noise is encountered...it is normally a failure of the compressor to be lubricated or charged properly. Just my $.02 worth on that issue.

Use a replacement R4 service the system properly (no recharge by cans) and the system should cool as well or perhaps...a bit better than 12.

One word of advice...the condenser on this vehicle can be installed upside down....make sure it is installed properly.....the flow does make a drastic difference.

Any questions..post them....someone will respond.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

TRB on Sat July 09, 2011 4:36 PM User is offlineView users profile

Ice, are those the 6mm condenser or a veined PF model?

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

kd7kmp on Thu July 14, 2011 10:11 AM User is offline

Thanks for the help, guys. I really appreciate it.

Kevin

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I've already done a search!

kd7kmp on Thu July 21, 2011 2:24 PM User is offline

I am finishing up the conversion, but I have one question left...the TXV bulb was simply clamped to the rear evap tube. Should I wrap Prestite tape around it, or is it not a big deal? Thanks.

Kevin

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I've already done a search!

iceman2555 on Thu July 21, 2011 5:42 PM User is offlineView users profile

Clamp and insulate the temp sensor bulb of the rear evap.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

kd7kmp on Fri July 22, 2011 9:59 AM User is offline

Hey all,

I got everything put in, drew a vacuum for 30 minutes (which it held), and charged it with 4 pounds of R-143a which is a bit less than 80% of the original 5.25 lb R-12 charge. It was 93 degrees when I charged it. Parked with the engine at idle I was able to get the vent temp down to about 58 degrees; pressures were around 50 psi for the low side and 300 psi for the high side. At 2000 RPM the vent temp was around 53 degrees; low side pressure was around 50 with high side around 275. I took it for a spin around town where vent temps dropped to about 48 degrees; I don't know what pressures were for this.

Although I'm quite happy with the performance, I'm wondering if I need to add a bit more refrigerant. To me the pressures look to be okay, but I would expect the low side to be a bit lower. The new condenser is a 6mm unit which appears to have smaller tubing than the oem tube and fin condenser. Anyway, what do you all think? Let me know.

Kevin

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I've already done a search!

mitchedo on Fri July 22, 2011 8:10 PM User is offlineView users profile

I have done this conversion on a 1991 Suburban V2500. I bought a parallel-flow condenser and fittings to fit to it. I then went to EVCO House of Hose and had my factory lines rebuilt with new hoses and the new fittings. I'm in Bountiful if you want to come by and have a look sometime.

It never did work as well as R-12, but it works reasonably well except for a slow leak I've had a difficult time chasing down. I think I've traced it to the splice Tunex put on the evaporator when they totally hosed my system and charged me $800 for the privilege.

I bought all my stuff from the site sponsor, and can attest that Tim is a stand-up guy.

edit: looks like I should have read to the end of the thread before posting. You seem to have good performance out of yours. Did you adjust the low pressure cycle switch to compensate for the difference in P/T curve for R-134? ...might give you a bit cooler vent temps.

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Doug
Home of the "Tunex Suburban Disaster"

Edited: Fri July 22, 2011 at 8:13 PM by mitchedo

kd7kmp on Tue July 26, 2011 2:22 PM User is offline

Doug,

I've purchased lots of components from the site sponsor in the past for replacement pieces on other cars. They're great to work with. As to adjusting the LPCS, I can't get the low side below about 50 psi at this point. I only have 4 lbs of refrigerant in the system now. I may try adding a bit more to see what happens. We'll see.

Kevin

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I've already done a search!

iceman2555 on Tue July 26, 2011 5:55 PM User is offlineView users profile

What type condenser did you obtain for this unit?
Also, it appears that the system is a bit undercharged. Suggest to work up to the 90 % charge rate. A valid test for correct charge is to measure the inlet and outlet temps of the evaporator. MAX AIR/DOORS OPEN/HI BLOWER/ENGINE AT IDLE. Measure the inlet temp of the evap (cold side of the orifice) and the outlet (before the accumulator inlet). The vehicle should be operated with both units operational for about 10-15 minutes. Measure the temps as suggested. The temps should be as near to each other as possible. Temps should be within 5 degrees of each other. Ideally the inlet should be a bit warmer. If the outlet is more than 8 degrees warmer...add a couple oz of refrigerant and retest. Must allow system to stabilize prior to testing.
If excessive pressures are encountered....it may be necessary to add additional cooling for condenser...do not remove refrigerant to adjust pressure. This undercharge will effect lubricant flow and result in a serious compressor failure.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Tue July 26, 2011 5:57 PM User is offlineView users profile

When the system is properly charged...there should be no need to adjust the LPCO switch. Of all the completed retro's we have never made this adjustment.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Tue July 26, 2011 6:01 PM User is offlineView users profile

Should have taken time to completely read your post. With the 6mm you should not have to cut back on the re charge rate...go for a 100% 134a to 12 recharge. But do the test suggested in my earlier post.
Also do a temp drop test on the condenser. Should see 25-29 degrees.
Let us know...sounds like all is working pretty good.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

kd7kmp on Tue July 26, 2011 11:33 PM User is offline

Iceman,

I'll do what you suggested. Thanks for the help.

Kevin

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I've already done a search!

iceman2555 on Tue July 26, 2011 11:46 PM User is offlineView users profile

The 6mm pic was one of the upgraded condensers utilized with 134a. This change alone solves many of the issues associated with retro fitting a vehicle.
Not sure if we talked about a fan clutch...but insure that this is operational.


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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

kd7kmp on Fri July 29, 2011 8:39 PM User is offline

After adding the last pound of refrigerant the compressor started cycling the way it should, pressures came down some and I get vent temps around 45 degrees driving down the road. Thanks for all the help.

Kevin

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I've already done a search!

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