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Old 04-30-2018, 07:49 PM   #26
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Just filled with enough Freon that the compressor should have kicked on but it didn’t. I’ve jumped ot before quickly to hear it run so I know it isn’t seized. Any other reason it wouldn’t kick on? Fuse number 9 is good.
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Old 04-30-2018, 08:04 PM   #27
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Alright I just jumped the low pressure cutoff thing that connects to the drier and the compressor cycled. Is it safe to leave this jumpered for 10 minutes or so to see if AC gets cold? I had it jumped for about 30 seconds and the compressor didn’t kick off. Don’t wanna over pressurize anything.
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Old 04-30-2018, 08:36 PM   #28
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Added some more R134 and here's what it's doing. Condenser doesn't even get warm and AC doesn't get cold. Any idea what's causing this? Gonna try to grab some real manifold gauges soon.



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Old 04-30-2018, 08:57 PM   #29
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The 134a system in my 93 wagon was full like that and was also cycling quickly like that while not cooling. Turned out the system was low on 134 and my gauge was lying about it being full. They hovered out the refrigerant and weighed it. There was a bit less than half of what it should have had in there. Once they filled it and leaked checked it. The system was worked well since then. thankfully 134 service is the cheapest at a shop.
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Old 05-01-2018, 09:38 AM   #30
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I would take it to a shop and have them recover the 134 you put in so you can replace that crusty, tired accumulator and pressure switch. Those pressure switches are known to fail and look just fine, much like the junction block sensor in the brake system.
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-My car: White 1991 244, 308k miles. B230F LH2.4, AW70, R134a retro. Thrush glasspack, anthracite refinished Coronas
-Wife's car: White 1990 244DL, T cam, 190k miles.B230F LH2.4, AW70 w/aux cooler, Duracool AC w/condenser fan, purple refinished Virgos, tow hitch, ipd wagon overload springs.
-PSM 2002 Subaru WRX wagon: 120k miles, Perrin TBE, Perrin turbo inlet, intake, and Y-pipe, GrimmSpeed cross pipe.
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Old 05-01-2018, 09:56 AM   #31
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I would take it to a shop and have them recover the 134 you put in so you can replace that crusty, tired accumulator and pressure switch. Those pressure switches are known to fail and look just fine, much like the junction block sensor in the brake system.
Accumulator=receiver drier? Gonna throw some manifold gauges on there today.
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Old 05-01-2018, 12:46 PM   #32
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You need to recover the refrigerant and weight it. Guages only tell you part of the story.

When I have a car that won't blow cold, the very first thing I do is recover it so I know if it's a low or overcharge issue. The machine is about $5k.

After I recover it. I vac it down and make sure it holds 29" of vac during and after the procedure.

Then I blast the specified amount of Freon back in there and recheck the system.
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Old 05-01-2018, 07:41 PM   #33
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Where is the high pressure port on a 1990 740? Trying to hook up manifold gauges.
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Old 05-02-2018, 02:25 PM   #34
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Bump. I have been reading around and maye there is no high side port on this r12 system. How are you supposed to do proper AC work without reading both sides of the system? I have a set of manifold gauges but cannot even use them.
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Old 05-02-2018, 02:49 PM   #35
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Yeah, Volvo was cool like that. My 93 wagon only has the low side. but it is still good for servicing the system. The refrigerant is sucked out and added via low side. The vacuum is drawn on the low side so you should be fine.
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Old 05-02-2018, 03:04 PM   #36
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Bump. I have been reading around and maye there is no high side port on this r12 system. How are you supposed to do proper AC work without reading both sides of the system? I have a set of manifold gauges but cannot even use them.
I'm pretty sure the high side port is on the back of the compressor.
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Old 05-02-2018, 03:17 PM   #37
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Yeah, Volvo was cool like that. My 93 wagon only has the low side. but it is still good for servicing the system. The refrigerant is sucked out and added via low side. The vacuum is drawn on the low side so you should be fine.
Yes but every source I’ve found has said that in order to do proper work, high and low sides should be considered.
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Old 05-02-2018, 03:18 PM   #38
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I'm pretty sure the high side port is on the back of the compressor.
I will look again but it did not look like the correct fitting. Perhaps my car still has the r12 fitting on the high side.
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Old 05-02-2018, 03:27 PM   #39
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Yes but every source I’ve found has said that in order to do proper work, high and low sides should be considered.
That is true if the compressor is an unknown. If you are reasonably confident in your compressor then using just the low side for service will work. I've had mine worked on several times and the shop didn't say anything. They may use some type of adapter that I don't know about but my system is still stock with only the low side port.
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Old 05-02-2018, 03:29 PM   #40
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That is true if the compressor is an unknown. If you are reasonably confident in your compressor then using just the low side for service will work. I've had mine worked on several times and the shop didn't say anything. They may use some type of adapter that I don't know about but my system is still stock with only the low side port.
I’m not confident on anything in this car. If I have a shop evac the system and hold a vacuum, can this be done on just the cold side? I’m really hoping the compressor still compresses. She is needing cold ac asap.

Should I also replace the orifice tube on this 740? Not sure where it’s located or if it’s bad but it’s a very very cheap part.
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Old 05-02-2018, 03:39 PM   #41
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I would replace the orfice tube if it has one. Then pump it down. The port should be on the back of the compressor. I have a 93 240 I can go check it if needed. You can barrow a vacuum pump from autozone. When filling with freon, make sure you bleed your gauge or you will get air in the system (not good.)

You really need to get high side guage on there. Ive seen where the low side looked fine but the high side was sky high. If you need help you can call me and I will walk you thru it. But you need some gauges (autozone loaners if needed) and a vacuum pump. And some patients.
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Old 05-02-2018, 03:45 PM   #42
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You only need one side to recover and recharge. Being able to read the high is nice, but not completely required.

I just fixed the AC in my 1990 240 with just the low side, but as u told you, I use a machine to weigh the proper amount of Freon.

Just slapping a can of auto parts store stuff in there isn't the correct method.

Some shops only charge you for the refrigerant. I would have it recovered. Do a new drier and seals on those hoses, find a way to vac it down, then add the proper WEIGHT of refrigerant and measure the vent temps and feel for a hot outlet and cold inlet of the compressor hoses.

Low side will stay high if the compressor is shot.
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Old 05-02-2018, 04:16 PM   #43
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I would replace the orfice tube if it has one. Then pump it down. The port should be on the back of the compressor. I have a 93 240 I can go check it if needed. You can barrow a vacuum pump from autozone. When filling with freon, make sure you bleed your gauge or you will get air in the system (not good.)

You really need to get high side guage on there. Ive seen where the low side looked fine but the high side was sky high. If you need help you can call me and I will walk you thru it. But you need some gauges (autozone loaners if needed) and a vacuum pump. And some patients.
I have a set of manifold gauges but I will need to rent a vacuum pump. Do I need to completely evacuate the system before pulling a vacuum? Also, do I need to replace the drier and the orifice tube before or after pulling a vacuum? Also your 240 uses 134 so it may be different.
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You only need one side to recover and recharge. Being able to read the high is nice, but not completely required.

I just fixed the AC in my 1990 240 with just the low side, but as u told you, I use a machine to weigh the proper amount of Freon.

Just slapping a can of auto parts store stuff in there isn't the correct method.

Some shops only charge you for the refrigerant. I would have it recovered. Do a new drier and seals on those hoses, find a way to vac it down, then add the proper WEIGHT of refrigerant and measure the vent temps and feel for a hot outlet and cold inlet of the compressor hoses.

Low side will stay high if the compressor is shot.
Okay so I can pull a vacuum just off of the low side and it’ll be fine. Should I replace orifice and drier before pulling a vacuum? I know I need to ‘evacuate’ the system before replacing parts. Last I checked, a vacuum pump can both evacuate the system and pull a vacuum. I had thought you needed a special machine to evac the system.

I was going to just take it to a shop until I realized how expensive AC work is.

I think the 740s system is holding pressure so I do not believe there is a leak. Something weird is definitely going on though.
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Old 05-02-2018, 05:02 PM   #44
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So to evacuate and vacuum the system I need a vacuum pump. Can I vacuum and evacuate from the low pressure side only since i cannot access the high pressure side? After that I want to fill with duracool and see what it does.

Another question: when I bypassed the low pressure switch on the drier, compressor ran constantly. When I plugged it in it cycled rapidly. How do I know if this switch is bad, and what tells the compressor when to cycle on and off? Surely it’s not the ecu in a car this old.

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Old 05-03-2018, 12:48 PM   #45
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So to evacuate and vacuum the system I need a vacuum pump. Can I vacuum and evacuate from the low pressure side only since i cannot access the high pressure side? After that I want to fill with duracool and see what it does.

Another question: when I bypassed the low pressure switch on the drier, compressor ran constantly. When I plugged it in it cycled rapidly. How do I know if this switch is bad, and what tells the compressor when to cycle on and off? Surely it’s not the ecu in a car this old.
The low pressure switch is simply an on/off switch. The fact the compressor came on at all when the switch was in the circuit tells you it is working as it should. Yes, simply vacuum the system down using the low side port. That will evacuate the entire system. Once you do that, charge it by weight. You an get close enough since you know how much each can of refrigerant holds. Weigh a full can and you will know exactly how much you have put in the system if you keep track of the weight of the last can needed to fill the system. Math is your friend, utilized it.

I took a look when I was at my shop yesterday. Some of the R-12 7/9 series compressors have a high side port on the back of the compressor, some don't. Volvo used 2-3 different manufacturers for their compressors.
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Old 05-03-2018, 02:20 PM   #46
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The low pressure switch is simply an on/off switch. The fact the compressor came on at all when the switch was in the circuit tells you it is working as it should. Yes, simply vacuum the system down using the low side port. That will evacuate the entire system. Once you do that, charge it by weight. You an get close enough since you know how much each can of refrigerant holds. Weigh a full can and you will know exactly how much you have put in the system if you keep track of the weight of the last can needed to fill the system. Math is your friend, utilized it.

I took a look when I was at my shop yesterday. Some of the R-12 7/9 series compressors have a high side port on the back of the compressor, some don't. Volvo used 2-3 different manufacturers for their compressors.
Awesome, thanks. There looks to to be a threaded nipple on the back of the compressor, maybe even 2. Any way to tell which one is for the high pressure side? I assume it’ll be on/near the smaller high pressure line. Plan today is to vacuum down the system with a rented AutoZone vacuum pump. Hopefully I can boil out all the moisture and hold vacuum for 30 minutes.
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Old 05-03-2018, 02:24 PM   #47
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The nipples line up with the hard lines. A 240 compressor has both high and low pressure ports on the back. You can have a compressor with both, with only a high side port, or, none at all.
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Old 05-09-2018, 05:29 PM   #48
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Getting ready to order some parts.

What brand receiver drier do I need? They range anywhere from $12-$32.
Something like this four seasons brand work? Found it for like $16 on Rock Auto.

Then I was assuming it would be a good idea to also purchase an orifice tube which if I'm not mistaken is the same as an expansion valve. Anything else I'll need besides duracool, a vacuum pump and manifold gauges?
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Old 05-09-2018, 06:00 PM   #49
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I know I've been talking about duracool but man it's pricey. Think I'm gonna go with some ES12-A found here. I will probably get the industrial stuff. Gonna have a few more questions about charging once it arrives. It says 6oz is equivalent to 16oz of r134a so I need to know how to take that into account when filling.
http://autorefrigerants.com/hydrocarbon-refrigerants
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Old 05-09-2018, 08:51 PM   #50
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A car has either and orifice or thermal expansion valve. Never both.

Get new seals, orifice, and drier.
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