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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.

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

Post by abscate »

Go to a two stage 3 cfm electric vacuum pump, no air driven crap

It will pull To 28 inches vacuum in seconds. When you have it all together correctly , it will hold overnight.
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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 »

abscate wrote: Sun May 19, 2019 7:59 pm Go to a two stage 3 cfm electric vacuum pump, no air driven crap

It will pull To 28 inches vacuum in seconds. When you have it all together correctly , it will hold overnight.
Good deal, I'll pick up one of those when I'm ready to fix this!
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Re: Recharging A/C... fan not coming on

Post by xHeart »

jimmy57 wrote: Sun May 19, 2019 10:48 am The fan runs due to sensed high side pressure. It will need to have something close to 1/2 of the refrigerant charge before the pressure would be high enough for ECM to run the fan.

[...]
When you are adding refrigerant with engine running or doing any a/c diagnosis you run engine at 1200 RPM or a little more. This is standard a/c service practice. All vent temps and all pressures you will find in any reference will assume you have system at a speed where compressor is at a speed where it works at its rated displacement. The other standard diagnostic settings are windows closed, fan at 3/4 speed, and recirculated air setting.

[...]
Evacuating the system isn't going to make any noticeable difference in charging speed. It is to get the moisture out and to get the air out that can dilute the refrigerant a wee bit. The refrigerant needs to go in slow when it has to run to charge. Too much liquid going in washes away the oil from compressor and you can get too much liquid on top of pistons to be compressible and cause compressor failure.
Tons of good info jimmy57, thank you.

Our 1997 850 with close to 178,000 miles will see its 24th summer. But AC cooling has been intermittent for past 4-5 summers. Last year, an AC recharge attempt lasted a 3 mile drive.

This weekend, I checked the compressor clutch gap, it was 0.63mm. So after placing 3 zip ties, the clutch gap closes to 0.25-0.30mm all around. Ran the engine/AC but the clutch did not engage, therefore, suspecting low refrigerant charge.

For next step, unless you feel EVACUATING procedure is premature, the 1200-1500 RPM method for filling appears logical for diagnosing.

You say "That car has a pressure switch on the low side line behind the engine that is used for compressor clutch control." Is this applicable to 1997 850? ITEM #45 in diagram below.

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

Post by abscate »

Yes, your 1997 has the switch in series with the clutch voltage commanded by the ECC control unit. If you jump that switch with wire with AC commanded on, it will engage the compressor clutch.

The most common point of failure is the evap core inside the climate unit - dash has to come out to fix.
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Re: Recharging A/C... fan not coming on

Post by wizechatmgr »

abscate wrote: Mon May 20, 2019 2:33 pm Yes, your 1997 has the switch in series with the clutch voltage commanded by the ECC control unit. If you jump that switch with wire with AC commanded on, it will engage the compressor clutch.

The most common point of failure is the evap core inside the climate unit - dash has to come out to fix.
Expect a full two days to do that core swap unless you want to kill yourself.
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Re: Recharging A/C... fan not coming on

Post by RickHaleParker »

Just a heads up. I got several cans of R134A from Walmart that will screw on both of my hoses but won't discharge. Even with a leak, he should of been able to feel the can get lighter.
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Re: Recharging A/C... fan not coming on

Post by callahanoffroad »

RickHaleParker wrote: Mon May 20, 2019 3:27 pm Just a heads up. I got several cans of R134A from Walmart that will screw on both of my hoses but won't discharge. Even with a leak, he should of been able to feel the can get lighter.
This happened to me with some pag oil from Walmart last summer.
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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 »

That's interesting. The can I'm using is from Walmart. Maybe I should try my other can I got at Autozone.
'00 V70R Venetian Red/Charcoal M56 Swapped 200k
'03 S60 2.4T Silver/Black 118k
'07 XC90 V8 AWD Sport Titanium Grey/Black 174k
'91 944 Turbo Dark Green/Beige 175k
'92 245 Base White/Beige 249k
1998 V70 GLT Black/Beige 205k
'99 BMW 528i
'01 Mountaineer 5.0
Sold-
2000 S70 GLT Mystic Silver/Taupe 253k
1993 944 Base Beige/Beige 221k
1998 S90- Silver/Gray 207k
1995 850 GLT Tropic Green... crushed
2001 S60 2.4T Black/Black 230k
1988 744 Turbo M46 Beige Metallic/Beige 188k
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Re: Recharging A/C... fan not coming on

Post by bmdubya1198 »

xHeart wrote: Mon May 20, 2019 11:56 am Tons of good info jimmy57, thank you.

Our 1997 850 with close to 178,000 miles will see its 24th summer. But AC cooling has been intermittent for past 4-5 summers. Last year, an AC recharge attempt lasted a 3 mile drive.

This weekend, I checked the compressor clutch gap, it was 0.63mm. So after placing 3 zip ties, the clutch gap closes to 0.25-0.30mm all around. Ran the engine/AC but the clutch did not engage, therefore, suspecting low refrigerant charge.

For next step, unless you feel EVACUATING procedure is premature, the 1200-1500 RPM method for filling appears logical for diagnosing.

You say "That car has a pressure switch on the low side line behind the engine that is used for compressor clutch control." Is this applicable to 1997 850? ITEM #45 in diagram below.

Image
I believe the low pressure side switch is #21 on that diagram.
'00 V70R Venetian Red/Charcoal M56 Swapped 200k
'03 S60 2.4T Silver/Black 118k
'07 XC90 V8 AWD Sport Titanium Grey/Black 174k
'91 944 Turbo Dark Green/Beige 175k
'92 245 Base White/Beige 249k
1998 V70 GLT Black/Beige 205k
'99 BMW 528i
'01 Mountaineer 5.0
Sold-
2000 S70 GLT Mystic Silver/Taupe 253k
1993 944 Base Beige/Beige 221k
1998 S90- Silver/Gray 207k
1995 850 GLT Tropic Green... crushed
2001 S60 2.4T Black/Black 230k
1988 744 Turbo M46 Beige Metallic/Beige 188k
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Re: Recharging A/C... fan not coming on

Post by abscate »

#21 is the high pressure switch. It has three electrical connects. Be careful with that puppy, and look up the price on FCP if you want to know why,

You can tell the #45 is the low pressure side since it comes after the evaporator, after expansion. It is also on the same line as #31, the fill port.
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