1993 945NA R-134a system. What should the High side & Low side pressures be at idle & 2000 RPM? What should the vent temps be? A friend of mine is going to check & service if needed. Is there anything unique to this car that I should tell him about? Thanks in advance for any help. I have checked the FAQ, but I didn't see any figures for an original 134a system.

In addition to Bob's tip below, tell your friend there is no place to sample High Side pressure on the '93 940 (like mine). If the fan comes on Low, the pressure got up to 260 psi. If High, then it reached 334psi.

I assume the Low Side should cycle between 45psi (Compressor comes on) and 23psi (Compressor cuts off).

I'm currently having a problem with excessive Low Side pressure (40-48), so my compressor runs all the time. I think the LS pressures are analogous to the temperature at the evaporator, so mine isn't getting cold enough to cycle the compressor clutch.
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Lucid,

I'm just curious about the fan. I recently converted a friend's '90 740GLE to R134a using the conversion kit from FCP Groton. When I charged the system and let the car idle while drawing the R134, I noticed that the electric fan in front of the condensor never came on. I'm wondering if there was something wrong with the car, or if the electric fan comes on only at certain times. Does anyone know the answer? It seems like the condensor would exchange heat more efficiently if the fan were running anytime the compressor is running.

Robert

"It seems like the condensor would exchange heat more efficiently if the fan were running anytime the compressor is running."

I agree, and I think many cars have the fan wired to come on with the compressor clutch. But on mine (which I'm just learning about), it doesn't work that way. Maybe because the compressor cycles on and off on normal operation.

Instead, it has the 2 pressure sensors I mentioned above, one for Low speed and onother for High speed. It's called a "CCOT" A/C system, for Clutch Cycling, Orifice Tube. The OT does the job of the Thermal Expansion Valve in the continuous running systems, as I understand it.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I found the answer to my question. In the faq, there is an entry from Rob Bareiss, whom I regard as the Grand PooPa of Volvo Knowledge, that says, "[Response: Rob Bareiss] YES, your electric fan is supposed to be on AT ALL TIMES when the AC is running.".

My friend's A/C that I converted is not cooling very well. I'm betting it's because the electric fan is inoperable. That will be my first place to look in diagnosing the problem.

I don't like to disagree with Rob, but believe his statement, "YES, your electric fan is supposed to be on AT ALL TIMES when the AC is running.". does NOT apply to all Volvo A/C systems.

It may be true for systems that use the TXV I mentioned above, but I have been spending a lot of time in the Volvo Climate Control manual and Wiring Diagrams for my '93 940.

These books show that the ONLY switches controlling the ONLY fan are the low A/C pressure one for Low Fan Speed, and either the high A/C pressure OR the high radiator temperature for High Fan Speed.

It may well be that the earlier 740 doesn't work like my 940.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

I have a late 1991 240 and the fan is single speed and is also conroled by a switch in coolant line, when the compressor cycles off the fan shadows it, when compressor cycles on so goes the fan. This is factory from Sewden and not a add on. So it is possible to have the conrol switch inside the car "AC on" and still have the fan cycle on/off piloted by the compressor actions. I know this for a fact because my fan failed and I traced problem back to the switch in coolant line, I just jumped it out and now my fan runs constantly whenever the AC slector switch is "AC on".

go to http://www.aircondition.com/ download the acadvisor program on the left coloumn of the page. it will tell you what the properpressure forthe outside tempshould be
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '82 Mercedes 300SD