Air conditioning system questions not answered elsewhere

[FireFox31]

I am trying to learn more about the 2000 V70 air conditioning system. This will help me either repair it or diagnose it so I can guide a professional to repair it (without them misleading me into costly work). I've read many A/C threads here on MVS, but have some questions which weren't answered elsewhere. This is a follow up to my original A/C thread.

Q: How can I tell if my compressor is on?
A:

the compressor is on when the clutch engages. the drive belt continuously moves the pulley so if you aren't familiar you may not know where to look. basically in laymans terms the middle metal piece will spin when the clutch is engaged and the compressor is on.

Q: Where is the low pressure cut-off switch?
A:

There is a black metal line on passenger side of engine compartment behind engine. It comes out of firewall next to a silver/aluminum line that is smaller. On the black line is a silver and white switch with a black connector on it. If you depress the metal loop on the side of connector and unplug it. Now with engine running and everything set so the A/C should be running, bend a paper clip into a "U" and bridge the two metal terminals down in the connector.

Q: Where is the temperature cut-off switch? I heard it can fail and can be jumpered during diagnosis.
A: The temp cut-off switch comes out of the driver's side of the compressor (opposite the clutch). It is a cylindrical brass piece with two wires coming out. To jumper it, trace the two wires back to where they connect to the wiring harness, disconnect them, and connect a wire between the two sockets on the wiring harness.

Q: Can I fill the system with a can of refrigerant even if the compressor isn't running? One post suggested that simply connecting the can to the low port and running the A/C would allow the refrigerant to enter the system, eventually starting the compressor.
A: See responses below. Essentially, yes.

Q: Can I visually inspect the evaporator without tearing apart the entire dash?
A: Yes, the evaporator is toward the driver's side of the cylindrical blower motor. Remove the blower motor and use a dental mirror to look left to see the evaporator. It should look perfectly shiny, and has surely failed if it looks corroded, greasy, or dark.

Q: When people do DIY work on their A/C, how do they suck out the refrigerant?
A:

DIY don't have recovery systems so step one to replacing components is to have it recovered by pros. This is free in smaller cities but many large city markets charge.

Q: Where is the accumulator / dryer?
A: The accumulator / dryer is the big tank below the passenger's headlight.

Q: Where is the high pressure port for measuring refrigerant charge with a manifold gauge set?
A: There is no high pressure port, at least on the 2000 V70.

Are there any other points of failure besides the evaporator, accumulator, clutch gap, condenser, low-pressure cut off switch, and temperature cut-off switch? Isn't there an A/C relay in the engine bay, driver's side, at the base of the windshield? And what made those clicks I heard from the front passenger's footwell when the compressor came on?

-- Edited to clarify questions and put answers inline.

[readallthebooks]

the compressor is on when the clutch engages. the drive belt continuously moves the pulley so if you aren't familiar you may not know where to look. basically in laymans terms the middle metal piece will spin when the clutch is engaged and the compressor is on.. as you noted there are various relays and pressure switches that will keep the clutch from engaging if theres some fault in the system.

if you are so low on refrigerant the clutch won't engage then yes, attaching the can and filling the system should eventually get the compressor to start. i've never had this not work on any car i've had BUT i've always seen instructions to jumper the low pressure switch if attempting to fill by the can doesn't work.

robert DIY has a youtube video on how to access the blower motor. there's also a much shorter video from volvoproject.

the compressor clutch on my car is loud, maybe it is on all 850s and v70s? the click you heard may just have been you hearing the clutch engaging, it can be heard from inside the car sometimes.

[abscate]

You will need about $200 of tools to service AC. The can with gauges from Walmart are not tools and are of limited use.

DIY don't have recovery systems so step one to replacing components is to have it recovered by pros. This is free in smaller cities but many large city markets charge.

You watch the end of the compressor to see if it spins. When the system commands AC, it pulls in the clutch and the end will turn with the belt. You will hear a click when this happens

Other than the clutch gap , very little can be diagnosed by inspection. An expert can observe condensation evolve from cold startup and get a good estimate of charge but most of us can't. Dry receiver dryer can come from many faults.

There is a DIY on removing the blower motor in this forum, I think I even wrote one for my 1999 V70T5M ( good search term)

viewtopic.php?f=1&t=62386&p=320751&hilit=1999+V70+t5

I don't think your 2000 came with a high pressure port, Volvo didn't add these until 2002 in the P2 line

[PeteB]

We also have an 850 with no A/C, not sure when it last worked.
Have you found a best thread on checking the gap?

This looks like an excellent thread on several A/C repairs and general tips:
viewtopic.php?f=1&t=81425&p=440820&hili ... ap#p440820

[erikv11]

We also have an 850 with no A/C, not sure when it last worked.
Have you found a best thread on checking the gap? ...

Checking the gap is super easy, you don't need a thread!

With the car off, look down and the gap is easily visible and accessible. Measure the gap with a feeler gauge set. Spec is 0.3-0.4 mm which is around 0.012 - 0.015 thousandths of an inch.

If the gap is up to 0.7 mm or so I usually adjust it. Use zip ties of the appropriate width (do the math, the gap will change by slightly more than the thickness of the tie) or dig to learn another gap method.

[volkans80]

Hi,

Lets assume low pressure switch is bad and jumpered. Can i use A/C?
If i can't, what if i connect a switch to pins and manually on and off can i use A/C?
Is there a temporary solution for using A/C with bad low pressure switch?

Thanks,

[PeteB]

Some pictures on page 3 of the bread clip fix and a few others:
viewtopic.php?f=1&t=63960&start=20

Robert DIY video of zip tie method:


Another from Robert DIY:

[erikv11]

Aha, I think I see what you mean PeteB, apparently you weren't just looking for info on how to measure the gap, as your post suggested.

Any time are wanting general information for a repair, start with the VRD, e.g. Ac shim fix are zip ties the new bread clips

[erikv11]

Hi,

Lets assume low pressure switch is bad and jumpered. Can i use A/C?
If i can't, what if i connect a switch to pins and manually on and off can i use A/C?
Is there a temporary solution for using A/C with bad low pressure switch?

Thanks,

This might get you started:
viewtopic.php?t=27648
viewtopic.php?t=64387

(probably not useful: Volvo 850 how to bypass ac thermal switch)

[volkans80]

Hi,

Lets assume low pressure switch is bad and jumpered. Can i use A/C?
If i can't, what if i connect a switch to pins and manually on and off can i use A/C?
Is there a temporary solution for using A/C with bad low pressure switch?

Thanks,

This might get you started:
viewtopic.php?t=27648
viewtopic.php?t=64387

(probably not useful: Volvo 850 how to bypass ac thermal switch)

Thank you. Actually everything is working. Only problem is low pressure switch (pressostat).