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Recharging A/C... fan not coming on

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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Re: Recharging A/C... fan not coming on

Post by xHeart » Fri May 31, 2019 8:43 am

bmdubya1198 wrote:
Tue May 28, 2019 9:23 am
...
I also grabbed some UV dye, I'm going to charge it with the dye this week and figure out this leak. With the adapter, I should be able to get it to take some refrigerant.
I'm waiting for warmer days to begin the procedure. But taking initial reading with manifold gauge to help chart next steps could happen this weekend. Weather here is still wet and on colder side but weekend forecast is sunny skies.

Reading manifold gauge took me to Pressure-Temperature Chart https://sporlanonline.com/literature/misc/Form1.pdf.


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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 » Fri May 31, 2019 11:15 am

xHeart wrote:
Fri May 31, 2019 8:43 am
I'm waiting for warmer days to begin the procedure. But taking initial reading with manifold gauge to help chart next steps could happen this weekend. Weather here is still wet and on colder side but weekend forecast is sunny skies.

Reading manifold gauge took me to Pressure-Temperature Chart https://sporlanonline.com/literature/misc/Form1.pdf.
It's certainly warm enough down here... the high today is supposed to be 87 and that's a cool down!
I just need to take care of some other stuff first on this car. VVT hub and instrument cluster need to be replaced. After that, I'll take care of the A/C.
As much as I'd like an actual cool down, I'm glad it's not raining!


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Re: Recharging A/C... fan not coming on

Post by xHeart » Fri May 31, 2019 8:19 pm

After few tries with manifold gauge I was able to pull R134a with engine running at RPM1800. At one point, before clutch engaged, the blue gauge was as high as 106 psi and white smoke started coming out of the low side connection -- turned the engine OFF.

10 minutes later tried again, and the ziptie compressor clutch kicked, but it engages/disengages fast, reads between 20-40psi. Air coming off the vents is still hot.

After I closed the low side valve and turned off the engine the gauge was at 82 psi.

It feels the self-sealing can is more than 1/2 full. Local Menards sells 12 oz. self-sealing for $4.90.

Is this a progress?


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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 » Fri May 31, 2019 9:37 pm

Hmmm... from what I've read, 20-40 PSI with the A/C on is correct range for these cars. I think the number I've seen is 37. I feel like mine was the same, but I know I had next to nothing in my system. It was doing the same thing though, the compressor was cycling on and off quickly but not running for more than a second or so each time.

I don't know how/why it would go as high as 106 PSI though. What could be wrong that it would go that high?


2000 V70R Venetian Red/Charcoal M56 Swapped 190k
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Re: Recharging A/C... fan not coming on

Post by jimmy57 » Fri May 31, 2019 10:18 pm

Something is screwy with these cans. I use 30# cylinders at shop but I was at my sister's a few hundred miles from home and topped up her vehicle with a Wal-Mart can with gauge hose affair and had no problems with it. On P80 with cycling clutch switch system the compressor will cycle rapidly until the charge is up to 75% or above. The pressure on low side will be 23-44 because the cycling switch turns comp on and off in that range. With compressor off and with charge of about 20% or more, the equalized pressure will be the static pressure of R134a. That pressure is very close to psi= F temp up to 80F and then the curve for gas pressure gets more steep so component temps of 95F would be about 105 psi. The increased gas pressure at elevating temps is why R134a systems had to have better condensers and why R12 systems switched over to R134a (back when that was a thing) did so bad until you were going over 40 mph.
Back to the problem at hand: If you have the engine above 1200 rpm and blower at no more than 3/4 speed then the low side pressure will let refrigerant go in. If you unplug the cycling switch and jumper the pins with a piece of wire, even a paper clip, you will stop the pressure changes and it will go in faster. You can feel the low side line coming out of firewall behind engine and when it gets chilled you can stop and plug the cycling switch connector back on then. If I am not charging by weight on these I will see that it is charged enough to cool OK and then turn fan to lowest speed and watch for the low side pressure to drop to 22-24 and compressor to go off. I then turn fan to highest speed (at this point car should have cooled down inside to a decently cool temp) and then check to see that the low side line close to compressor is sweating a VERY cold. If the car is 75 deg inside and fully charged there is still enough refrigerant "boiling" for that line near compressor to have a 50F or cooler temp. It will not be this cold when car is still warm inside as the heat in evaporator is still enough to complete the evaporation of freon before the gas gets back to compressor. If the car is chilled inside and the line is not cold then add a bit more. The too much chrge test is on lowest fan speed it is reluctant to fall below 24 psi on low side and allow compressor to cycle. ALL OF THIS DONE WITH ENGINE OVER 1200 RPM, windows up, and recirc on. Again all of this conversation is about units with an orifice and that two pin pressure switch screwed into low side. Expansion valve systems on the P2 and P3 don't play by these rules.
If you happen to be working on the car on a 105F dy out in the sun with no shade your results will vary as the heat load is much higher and you may not get the car chilled to mid 70's or below sitting still. On SUPER hot days the system will not have enough air over condenser from cooling fan alone. You have to drive continuously over 40 MPH for 5 minutes or so and see if it cools the car down. Better yet, wait till later that evening when it cools off if that is possible.
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Re: Recharging A/C... fan not coming on

Post by xHeart » Sat Jun 01, 2019 6:42 am

jimmy57 wrote:
Fri May 31, 2019 10:18 pm
ALL OF THIS DONE WITH ENGINE OVER 1200 RPM, windows up, and recirc on. Again all of this conversation is about units with an orifice and that two pin pressure switch screwed into low side.
Thank you jimmy for delineating.
I'll work with it today. Rain is in forecast all day today with temps around 70ºF -- favorable to continue with it.

FWIW: after letting it sit and cool off overnight the low side STATIC pressure this morning is 48 psig/52ºF. Our home/garage has central HVAC so ambient F temp is relative.

Here is a pix from last night after closing valve and engine shutoff.
MVS_AC_0122.jpg
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Re: Recharging A/C... fan not coming on

Post by xHeart » Sat Jun 01, 2019 1:00 pm

jimmy57 wrote:
Fri May 31, 2019 10:18 pm
If you have the engine above 1200 rpm and blower at no more than 3/4 speed then the low side pressure will let refrigerant go in. If you unplug the cycling switch and jumper the pins with a piece of wire, even a paper clip, you will stop the pressure changes and it will go in faster. You can feel the low side line coming out of firewall behind engine and when it gets chilled you can stop and plug the cycling switch connector back on then. If I am not charging by weight on these I will see that it is charged enough to cool OK and then turn fan to lowest speed and watch for the low side pressure to drop to 22-24 and compressor to go off. I then turn fan to highest speed (at this point car should have cooled down inside to a decently cool temp) and then check to see that the low side line close to compressor is sweating a VERY cold. If the car is 75 deg inside and fully charged there is still enough refrigerant "boiling" for that line near compressor to have a 50F or cooler temp. It will not be this cold when car is still warm inside as the heat in evaporator is still enough to complete the evaporation of freon before the gas gets back to compressor. If the car is chilled inside and the line is not cold then add a bit more. The too much chrge test is on lowest fan speed it is reluctant to fall below 24 psi on low side and allow compressor to cycle. ALL OF THIS DONE WITH ENGINE OVER 1200 RPM, windows up, and recirc on. Again all of this conversation is about units with an orifice and that two pin pressure switch screwed into low side.
I found that 2 of the 3 zip ties had untied itself, so these were replaced. Jumped the pins to run the compressor clutch. 3/4 way into the 2nd can the line started to feel cold. Closed the valves and shut off the engine and then placed the plug back on at the switch.

Cabin temp was nicely cold at 56ºF. Started back again, and compressor kicked at low air as it should. Set the engine speed 1200RPM and finished the 2nd can. During this filling the compressor remained engaged, not cycling ON/OFF.

Final cabin temp after emptying the 2nd can was 46ºF.

Is this coming together?

At valve closed and engine shut off the gauge read 35psi. I could see and feel the cold sweating line. Here are the two pix:
MVS_AC_0126.jpg
MVS_AC_0123.jpg
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Last edited by xHeart on Sun Jun 02, 2019 7:54 am, edited 1 time in total.


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Re: Recharging A/C... fan not coming on

Post by abscate » Sat Jun 01, 2019 1:31 pm

What was your ambient temp xHeart?

35 F delta is good
40F is really good
45F is Master Chill, Samurai


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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 » Sat Jun 01, 2019 5:30 pm

Everything looks good to me! I'll have to get back into my A/C once I sort out this potential failing ECU.


2000 V70R Venetian Red/Charcoal M56 Swapped 190k
2001 S60 2.4T Black/Black 230k
2003 S60 2.4T Silver/Black 107k
2007 XC90 V8 AWD Sport Titanium Grey/Black 158k
1993 944 Base Beige/Beige :mrgreen: 221k
1992 Miata Mariner Blue/Black 146k
Sold-
1998 V70 GLT Black/Beige 193k
1998 S90- Silver/Gray 207k
1995 850 GLT Tropic Green... crushed
1988 744 Turbo M46 Beige Metallic/Beige 188k- Never should have sold it


Need used parts? PM me!

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Re: Recharging A/C... fan not coming on

Post by xHeart » Sat Jun 01, 2019 7:31 pm

I'm entertaining myself using recharged AC -- cabin feels different. Humming of compressor brings back memories of long summer drives. We've this car since new August 1996 -- almost everything works well in this car.

The ambient temp was reading 78ºF on the dash. The light next to AC switch has turned blue/purple after charge, it was orange/red before charge.

The cans were frosty and chill during the recharge -- I had gloves on.
Should I try to top up -- take it to 40-45 psi?

Thank you bmdubya for sharing your thread.


--
Golden Retriever | 2014D VIDA DiCE | 2013A XC90 +140mi/225km | 2001 V70XC 1st Owner +190mi/ +305km | 1997 Volvo 850 NA 1st Owner +180mi/ +289km
Past: German Shepherd | 1989 Volvo 740 GL | 1979 Volvo 240

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