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Discussion Starter · #1 · (Edited)
The car is a US version, 2008, 5MT. The AC system has been losing efficiency over the last year or two, so I decided to recharge it and check on it's health. The starting state before the AC recharge was a low side pressure of about 30 psi at 90f, and the clutch engaging intermittently about every 30 seconds, with an engaged period of about 3 seconds. I was able to recharge the system to about 50psi. However, the clutch will now no longer engage after restarting the car. I have waited several days before retesting, to rule out a heat soaked compressor clutch, but no luck.

I decided to pull up VIDA, but am having trouble understanding the information. I checked that cabin air temp, outside air temp, and evap air temp are within limits for compressor activation, and are accurate. The car is reporting an AC pressure of 365 kPa, which I understand is in limits. The pressure switch is reading as "On (continuous or audible)". Does this mean the car thinks there is an overpressure? Is this a bad A/C pressure switch? Is this reading coming from the high side sensor? To be clear, from what I can see from the data scope in VIDA, the car isn't even trying to request an compressor start.

Thanks

Image of select sensor data, graphed...
 

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The car is a US version, 2008, 5MT. The AC system has been losing efficiency over the last year or two, so I decided to recharge it and check on it's health. The starting state before the AC recharge was a low side pressure of about 30 psi at 90f, and the clutch engaging intermittently about every 30 seconds, with an engaged period of about 3 seconds. I was able to recharge the system to about 50psi. However, the clutch will now no longer engage after restarting the car. I have waited several days before retesting, to rule out a heat soaked compressor clutch, but no luck.

I decided to pull up VIDA, but am having trouble understanding the information. I checked that cabin air temp, outside air temp, and evap air temp are within limits for compressor activation, and are accurate. The car is reporting an AC pressure of 357 kPa, which I understand is in limits. The pressure switch is reading as "On (continuous or audible)". Does this mean the car thinks there is an overpressure? Is this a bad A/C pressure switch? Is this reading coming from the high side sensor? To be clear, from what I can see from the data scope in VIDA, the car isn't even trying to request an compressor start.

Thanks
Do a proper check on the AC system by putting a set of gauges reading the high and low side.
The gauge you get with a can of refrigerant is a waste of time and effort.
With gauges you get a starting point from which you can diagnose from there.
 

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Discussion Starter · #3 ·
I will have to head to a friends shop for a proper set of A/C gauges. In anticipation of that, I'd like to know the next steps.

The car's low side pressure sensor and the crappy gauge agree, however I will confirm this with a better gauge. Assuming that a third reading confirms the low pressure side pressure, then what to do with the high side?

The compressor will not engage, so what kind of readings should I expect to see on the high side service port? Assuming that I can confirm that the high side pressures are within spec, does this just leave a faulty high pressure switch?

I think more specifically, I want to know the meaning of the "ECM-A/C-pressure switch" entry. Does "On "continuously or audible)" mean that the car thinks the high side pressure is too high?
 

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I will have to head to a friends shop for a proper set of A/C gauges. In anticipation of that, I'd like to know the next steps.

The car's low side pressure sensor and the crappy gauge agree, however I will confirm this with a better gauge. Assuming that a third reading confirms the low pressure side pressure, then what to do with the high side?

The compressor will not engage, so what kind of readings should I expect to see on the high side service port? Assuming that I can confirm that the high side pressures are within spec, does this just leave a faulty high pressure switch?

I think more specifically, I want to know the meaning of the "ECM-A/C-pressure switch" entry. Does "On "continuously or audible)" mean that the car thinks the high side pressure is too high?
Depending on the outside temp;
http://rechargeac.com/how-to/ac-system-pressure-chart.
find out what the pressures are first.
Correct as required - vacate, check for leaks, recharge - are pressures now within specs.
 

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Discussion Starter · #5 ·
So are you suggesting that I can not know whether the data I have gathered suggests a bad high pressure switch? To take the action that you are suggesting would mean the possibility of vac and filling the system twice. Once to verify pressures, and a second time to replace whichever component is bad. Is that your advice?
 

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So are you suggesting that I can not know whether the data I have gathered suggests a bad high pressure switch? To take the action that you are suggesting would mean the possibility of vac and filling the system twice. Once to verify pressures, and a second time to replace whichever component is bad. Is that your advice?
I am suggesting you "first" put a set of gauges on to see what you have.
If your high pressure is way off - what are you going to do?
 

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Discussion Starter · #7 ·
I am suggesting you "first" put a set of gauges on to see what you have.
If your high pressure is way off - what are you going to do?
That makes sense. Being that it's going to be a week or two before I can either use my fiends garage, or find another shop which will actually just give me a pressure reading (I have called 3 shops, and they have said no to giving me a pressure read), then I want to have any parts I might need in hand before going through the process. If I can confirm the ECM-A/C-pressure switch reading relates to the high pressure cutoff switch, I want to order the switch anyway, regardless if I later find out that the switch isn't bad. If this reading is related to the low pressure side, and say indicates that the pressure is adequate, then I will hold off ordering any parts until I go through the pressure check process.

So again, how to I find out what this reading is, and what its current value means?

Thanks
 

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if the compressor clutch is not coming on then A/C gauges are going to be useless

50PSI is also too much on the low side, it should be around 40. usually fluctuates 38-45.
you can always let the freon out if you added too much recently and see if the compressor comes back on again, a can of freon is only 5$.
of course, stop killing trees when you can.
 

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The car is a US version, 2008, 5MT. The AC system has been losing efficiency over the last year or two, so I decided to recharge it and check on it's health. The starting state before the AC recharge was a low side pressure of about 30 psi at 90f, and the clutch engaging intermittently about every 30 seconds, with an engaged period of about 3 seconds. I was able to recharge the system to about 50psi. However, the clutch will now no longer engage after restarting the car. I have waited several days before retesting, to rule out a heat soaked compressor clutch, but no luck.

I decided to pull up VIDA, but am having trouble understanding the information. I checked that cabin air temp, outside air temp, and evap air temp are within limits for compressor activation, and are accurate. The car is reporting an AC pressure of 365 kPa, which I understand is in limits. The pressure switch is reading as "On (continuous or audible)". Does this mean the car thinks there is an overpressure? Is this a bad A/C pressure switch? Is this reading coming from the high side sensor? To be clear, from what I can see from the data scope in VIDA, the car isn't even trying to request an compressor start.

Thanks

Image of select sensor data, graphed...
I don’t know if you’re still having the issue but I had an issue with an intermittent ac that would blow cold for 20 mins or so before just running warm air. Turned out to be an issue with the ac clutch pulley and there are these little washer shims I had replaced on the inside and I haven’t had a problem since. https://youtu.be/p1EjB7_2jmQ
 
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