A/C Pressures after Conversion - Alfa Romeo Bulletin Board & Forums
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post #1 of 25 (permalink) Old 06-19-2012, 04:35 AM Thread Starter
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A/C Pressures after Conversion

The previous owner of my S did a cheapo conversion to R-134, but the compressor failed and I decided to do an almost full conversion.

New components installed:

1. New R-134a Sanden compressor (SD7H15 from Alfissimo)
2. New P-Flow condenser (see this thread: Parallel Flow Condenser Retro-Fit)
3. New Hannefin R-134 expansion valve
4. New Receiver/Dryer (from International Auto Parts)

I flushed the all the high pressure side hoses with mineral spirits and the spirits came out clean. Low side looked very clean.

4 oz of Ester Oil was added to the compressor prior to install. The system spec is 4.5 oz (AFAIK) and I figured there was probably still a half oz or so in the evaporator from the previous conversion attempt.

Everything installed with almost all new Buna 0-rings. The line from the evaporator to the POA valve was very very tight on both ends, so I decided to leave the old rings on either end of that hose. All the rest are R-134 spec o-rings.

Pulled a vacuum for 60 minutes. I then let it sit for about 45 minutes and it held the vacuum.

Charged the system with 3 - 12oz cans of straight R-134a (no stop leak, oil, etc). That makes for about 36 oz vs. the 44 oz spec for R-12. I charged the R-134 as gas through the low side fitting. I noted that it seemed to take the gas slower than the systems on my Jeep Grand Cherokees. Took about 15 minutes per can it seemed. Charged upright while rocking the can. I tried to keep the can warm as well.

I was surprised that after 12 oz or so went in that I still wasn't getting any cooling out the vents. After 24 oz, the pretty much the same, maybe a little cooling. Even after 36 oz, it wasn't cold. So, I let the system run. No unusual noises, compressor was quiet and ran continuously. The low side lines after a while started to get cold, but not what I'm used to with my other US made cars. High side lines were warm but not overly hot.

After a while I finally started to get some cool air out the vents (60s). HVAC system was on Recirc, manual full cold, fan speed 3. And BTW, it was not a hot day . . . ambient was in the mid 70s.

I then took it out on the road and that helped get the vent temp down to the high 40s or so.

In all, it just seemed that it took quite a while to "settle in" whereas in my other cars, that doesn't happen.

Now for the pressures. The fan kicks on normally (I have not done Steve's high speed fan mod, nor the heater shutoff valve yet, but will). Here's what I'm getting at idle, off idle, and static pressures.

I'm a little concerned that the low side is too high, and also that the static pressure is too high. The pressures hold pretty steady, but you can see the high pressure rise until the radiator fan kicks on, then it comes back down normally.

Still not satisfied with the air temp out the vents. Anybody see anything that I'm doing wrong?

*************************

UPDATE: Checked this morning and static pressure was 70 psi engine cold. High pressure was probably just hot engine compartment . . . Duh. Pressures this morning with a cold engine are:

Idle: Low 28 psi, High cycling 160-230 psi
Off Idle: Low 34 psi, High cycling 170-230 psi
42F air out the vents. Ambient temp about 70F

ADDITIONAL UPDATE (System has been running well for about 6 weeks)
(Hot day >90F, engine at operating temperature)
Low 38 psi steady, High 175 psi steady, both measured at idle
45F vent air after cooling down cabin
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91 164S

Last edited by Roadtrip; 04-27-2013 at 06:10 PM.
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post #2 of 25 (permalink) Old 06-19-2012, 09:46 AM
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I rechecked my 164L

System low side went up to 40 as high side rose to 220 and fan came on low side dropped back to 35 as high side came down to about 150 when fan cut off.

Shutting system off low side went up to about 100 and high side stayed about 150.

I would add another 12 oz can to your system and see if that helps.

I put cans in hot water bucket to force gas in faster.
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Daily drivers: USA models - 1991 164S Black Beauty II ALFISTO;

Daughter's current ride: BB1 my 164L and Her Granddads 2002 Ford Taurus is back up.

New parts hauler but not car hauler 2004 Jeep Grand Cherokee Overland 4.7L H.O. V-8

Needing TLC non-blackbeast the 93 164L

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post #3 of 25 (permalink) Old 06-19-2012, 10:40 AM Thread Starter
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It's cooling well today. When I put the gauges on it, a gauge hose seal in my high side connection started to let go and I lost some gas before I could disconnect it. I'll check it again in a couple days. I might need to add a little to replace the bit that came out the connection, but I think 12oz will be way too much. I'm going to just let it run as it is right now for a few days and see how it does. I've got to get some new gauge set hoses anyway since the seals on a couple are shot.

The pressures I'm getting today very closely mirror yours.

John Stewart
74 Spider
91 164S

Last edited by Roadtrip; 06-19-2012 at 03:13 PM.
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post #4 of 25 (permalink) Old 06-19-2012, 05:37 PM
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Max idle low pressure should be about 45. Sometimes they like to be run for a while at speed to settle the A/C down and cool well. Maybe while the oil is being distributed in the system?

Red 1991 164S, Black 1991 164S, Red 1987 Milano, 1972 Berlina, 1973 Berlina rebuilding SPICA engine
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post #5 of 25 (permalink) Old 06-19-2012, 05:45 PM
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40F air out of the vents is pretty darned good! Any colder and you're going to start icing up. That may even be too cold: on the Milano the spec is something like 47F out of the vents to prevent icing.

Anyway, you're only going to get cooling in the car if there's air moving over the condenser. If it's like the Spider, the trinary switch should trigger the fans to run very shortly after the A/C turns on. If the fans aren't running when the car is sitting still you won't get any cooling.

Tom

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1963 Giulia Spider (1750 engine)
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post #6 of 25 (permalink) Old 06-19-2012, 08:44 PM
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Y'know what? I'm wrong. Spider fans cycle on at high side 220 and off at 180PSI. So it takes a bit for them to come on and then they cycle.

Carry on.

Tom

1991 Spider
1963 Giulia Spider (1750 engine)
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post #7 of 25 (permalink) Old 06-19-2012, 11:41 PM
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Radiator cooling fan should come on about 215psi on 164 and to further aid cooling be sure when green dot on over recirculation button on a/c panel recirc door on evaporator box behind false firewall actually closes.

Also check for good seal between evap box and blower motor housing at round connection joint. Hard to check all 360 degrees.

Another issue that can cause engine heat to get behind false firewall is bad rubber hood seal on top of false firewall. I have installed a smaller flexible hose inside that hollow seal so it will seal tighter against bottom of hood.

Also important that expansion valve pig tail sensor clipped to large copper tube and sealed with rubber tar tape from surrounding heated area. Later models also have frost switch sensor attached to same pipe and sealed with tar tape, too.

Earlier models have frost switch sensor tube going inside evaporator box into evaporator core like GTV6 and Milanos.

One thing that can't be easily checked is temp doors seals inside blower motor housing even if stepper temp lever closes doors. This is why we have installed manual shut off valve in heater hose coming off rear rear (front head on 12v and rear head on 24v V6 models).

Ciao, Alfisto Steve
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Daily drivers: USA models - 1991 164S Black Beauty II ALFISTO;

Daughter's current ride: BB1 my 164L and Her Granddads 2002 Ford Taurus is back up.

New parts hauler but not car hauler 2004 Jeep Grand Cherokee Overland 4.7L H.O. V-8

Needing TLC non-blackbeast the 93 164L

"A day without an Alfa whine is like a day without sunshine"

Last edited by Alfisto Steve; 06-19-2012 at 11:49 PM.
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post #8 of 25 (permalink) Old 06-20-2012, 08:54 AM Thread Starter
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Fan comes on normally with A/C, so the trinary switch is working correctly.

I also replaced the OEM fan switch with a 85-90 VW Golf 2-speed fan switch. Low speed fan 180F // High speed fan 195F vice the 198F/205F OEM. I also put a correction resistor inline with the gauge temp sending unit to make it more accurate with the IR gun. So far the A/C doesn't seem to have affected engine temp at all, but we haven't had any real hot days yet.

Seals on the boxes are good as I can tell. False firewall seal looks like new.

I haven't gotten any new monkey poop, so I had to use the old stuff. As soon as I can find some, I'll put new on the frost and expansion valve coils.

HVAC controls inside seem to be doing the job well. I can tell a difference in Recirc vs. outside air.

John Stewart
74 Spider
91 164S
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post #9 of 25 (permalink) Old 06-20-2012, 01:47 PM
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Next time you can wire the condenser fan to run at the get-go of charging or put a box fan in front, also like Steve already said, warm water in a bowl helps a lot to get the freon to flow in from the cans. I have had to do that on my 164 as well or it seems to take forever.
Charles

-'91 164L 5 speed 229k miles and counting
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post #10 of 25 (permalink) Old 05-31-2016, 05:29 PM
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Completed the modification and installation of a new Sanden SD7H15 compressor this weekend, and todayI finally got my AC working again after the front seal in my original 709 that had been rebuilt once before failed a couple of months ago.
With an outside air temp of 84F today, static pressure was 90 low side/90 high side.
With the engine running and the AC system on, average pressures were 30 psi low side/ 160 high side, and the pressures gradually increased to 44 psi low side/ 240 psi high side when the fan kicked on and the pressures dropped back to 30 psi low side/160 psi high side, and the pressures then cycled back up to 44/240. Got r56-58 degree air at the center vent (although air blowing under the driver seat felt cooler for some reason). In any event it's still humid here in Dallas, so that may be as good as I'm going to get.
I should add that I installed one of those VW fan switches a few years back, so the fan kicking on may be different than the Alfa spec for that reason.
Any suggestions?
Do the pressures look good/is the system over or undercharged on R134?

Last edited by CMalfa; 05-31-2016 at 05:33 PM.
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post #11 of 25 (permalink) Old 05-31-2016, 05:50 PM
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I should add also that I noticed that the foam around the evaporator looks to be in bad shape, at least from the top, anyway. Would jamming some new foam on top without removing the evaporator to replace the original foam help? Or just a waste of time?
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post #12 of 25 (permalink) Old 05-31-2016, 07:03 PM
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4Seasons 59010 - A/C system sealing tape

Anything you can do to keep hot air from getting sucked in around evaporator to fan housing coupling will help the cooling.

I buy 2 1/2" "monkey goo" a/c expansion valve sealing tape such as 4Seasons 59010 by the box (probably 50' roll). It works great to seal around coupling and expansion valve and lines.

http://www.streetsideauto.com/p/four-seasons-59010/ realistic price but out of stock

Way way bad Bad price https://www.amazon.ca/Four-Seasons-5.../dp/B000DCNG2E

Good price Four Seasons 59010 - Free Shipping on Orders Over $99 at Summit Racing

Ciao, Alfisto Steve
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Daily drivers: USA models - 1991 164S Black Beauty II ALFISTO;

Daughter's current ride: BB1 my 164L and Her Granddads 2002 Ford Taurus is back up.

New parts hauler but not car hauler 2004 Jeep Grand Cherokee Overland 4.7L H.O. V-8

Needing TLC non-blackbeast the 93 164L

"A day without an Alfa whine is like a day without sunshine"

Last edited by Alfisto Steve; 05-31-2016 at 07:13 PM.
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post #13 of 25 (permalink) Old 05-31-2016, 07:17 PM
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A 30 degree temperature drop from outside air to air coming out of the vent is very good! Your not far off that.

Red 1991 164S, Black 1991 164S, Red 1987 Milano, 1972 Berlina, 1973 Berlina rebuilding SPICA engine
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post #14 of 25 (permalink) Old 05-19-2017, 07:09 AM Thread Starter
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2017 Update to this thread.

It's been about 5 years now since I reconfigured my A/C system to R-134a. It is still running well. The system has been very consistent in losing about 12 oz of refrigerant during the year, which I attribute to the old non-barrier R-12 hoses.

I thought I'd post some pressures that you might expect from your system, should you do a conversion similar to mine and have to top off every spring.

Before adding 12 oz of R-134a today (OAT 80F):

Pressures:
Low 37-40 psi
High 170 psi

Vent temp 50F on recirc, fan speed 4

After adding 12 oz of R-134a:

Pressures:
Low 25 psi
High 200 psi
Vent temp 45F fan speed 4, and slightly lower with fan speed 2 and I expect even lower with car moving at speed and cabin cool.

John Stewart
74 Spider
91 164S
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post #15 of 25 (permalink) Old 05-19-2017, 10:31 AM
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Same deal here, I have to add a can every year to get it cooling again. I've gotten to the point that I just use a simple short hose, and don't even get the whole gauge set out. Just add a can in the spring it's good all summer. Same with the old 240 Volvo, the old R12 hoses just leak a bit I suppose.
CD

-'91 164L 5 speed 229k miles and counting
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