Hi everyone, new to site....first Volvo, 2001 V70 base non-turbo, standard trans. 233K miles....manual climate control.

The clutch on my AC compressor never engages when the dash AC button is pressed (lights on button works, red off-green on). But when I pull the relay and jump (3 to 5) it engages and blows ice cold air. I switched relays (w/ the horn) and that does not help.

From what I have learned the only other parts involved are maybe a pressure sensor near the evaporator/dryer (a engine coolant sensor?), maybe a under dash sensor and the computer.

Another thing I noticed is that with the engine running I get 12v at the relays pin 3, with the dash AC switch on or off? Is that normal?

 

Need a wiring diagram to diagnose. If compressor engages when you jump the relay and gives ice cold air, it's likely related to a sensor issue, although I would verify high side pressures with an A/C gauge set just to ease my mind.

 

The gauge was inconclusive? So I tried adding a can of coolant (to try to trip the sensor) ....it blew the line coming out of the compressor!

Instead of simple switches you can see, Volvo decided to put a complicated very expensive (3 prong) 'sensor' which you have to take the entire front of the car off to get to!
Or another (worthless) 'green' sensor you have to take the entire dash apart to get to!

It's also hard to get a schematic for these cars.

 

Since it cooled when you jumped the compressor, but has now blown the line off, there was clearly a high pressure condition, so the system was likely behaving correctly in NOT activating the compressor.

The most plausible scenario is that you were overcharged to begin with. There's no way to measure the amount of charge other than to recover the refrigerant and weigh how much was removed. Well, that option isn't exactly available now :-)

I'd recommend charging to the correct system spec at this point. Save yourself some aggravation and get an a/c gauge set if you're going to mess with this further so you can see what the high side pressure is doing...

If the factory charge level creates high pressures, then a possible blockage may exist.

 

You misunderstand, the line out of the compressor didn't blow until AFTER I tried adding coolant.
I wasn't sure what the gauge was showing (it's one that needs to be removed to add the coolant can).

I was thinking it needed more charge to get the pressure needed to get the 'sensor' to engage the system.
This is NOT a simple (hi or lo) switch, it's a 3 prong sensor that YOU CAN'T EVEN SEE....you have to take the entire front bumper off to get to it!

What a stupid, stupid, stupid design!!!
I can see why you haven't touched your 2002 AC....just try to find that 'sensor'.


This (practically unserviceable) 'sensor' seems to control the computer to work the AC? I believe that this HIDDEN 'sensor' keeps the AC from turning on if there was a low pressure condition....so I tried adding a can of coolant. That blew up my system.


Again, what a STUPID design.

 

No, I understood. A high pressure condition likely existed BEFORE you added refrigerant...just not enough to blow the line off.

Please - get yourself a gauge set (something like ) before going any further. Even a cheap harbor freight version of it is far better than just the low side gauge that comes on those cans of refrigerant.

If you hadn't gotten good cooling when you jumped the compressor, I'd have thought it was a blockage in the system. However, since you had good cooling when jumped, but clearly had high pressures, it pointed to an overcharge in my opinion. Once you added a bit more refrigerant, those high pressures skyrocketed even higher and blew the line off.

BTW, difficult-to-access components is the hallmark of auto a/c work in general. Evaporator changes are frequently a drop-the-dash kind of thing, and bumper removal to access the condenser is not at all uncommon.

 

I used a gauge, it actually / probably looked ok, but I never worked on AC before so I wasn't sure. If anything it was a hair LOW.

It only worked while jumping the relay....instead of normally turning off & on, it was on constantly (to read the gauge).

I was hoping adding coolant would get the 'sensor' to work.

Instead it blew the line where it crimps from solid to flexible.

So I now believe the (expensive, inaccessible) 'sensor' is / was faulty.


Before the 2001 model the high & low switches were easily accessible.

 

You had a high side gauge hooked up? What was the (high side) pressure when you jumpered the compressor? From your description, I suspect you only had a gauge hooked up to the low side....likely the kind that comes with some cans of refrigerant.

Why are you so insistent that it's a faulty sensor? If a line blew off, it was due to DANGEROUSLY high pressure. I'm not aware of any sensor in the system that can artificially create such high pressure. You need to find and fix the source of the high pressure. It was likely due to an overcharge as stated several times already.

Replace both the line AND the drier, add an ounce or two of refrigerant oil to drier (or whatever is specified in the manual for just the drier), recharge to factory spec (by weight), then check the pressures again, noting both ambient and vent temperatures (and need both low AND high side pressures). I'd HIGHLY recommend having a shop re-charge for you, as charging by cans isn't a very accurate means of getting the right amount (the can says 12 oz, but how much actually goes into the vehicle)? A shop will have a 30lb scale (doesn't get disconnected while charging) and will measure exactly how much goes into the vehicle. Plus, you need to pull a vacuum on the system prior to charging to remove all the air. I'm assuming that since you've never done this before, you don't have such equipment just laying around.

If, after recharging PROPERLY, you STILL have a high, high side pressure, then we'll need to look into the possibility of a restriction in the lines. However, there's a good chance your A/C will start working again once charged to factory levels. If, at that time, pressures are good, but you STILL have to jumper the compressor in order to run, THEN it will be time to look into sensor issues again.

Oh, another thing you probably already checked is to verify the relay actually works. Apply 12v to it (forget which terminals) and verify it "clicks" and makes continuity. Another way is to simply swap similar relays and see if it starts working (once the A/C is charged and such)

 

I ran the AC many times by jumping the relay w/ no problem. Only after adding a can of coolant did it blow the line.
THAT'S why I think ("so insistent") it's the 'sensor'.

That, and the guy I bought the car from said he had someone look at it and they kind of narrowed it down to a "switch".

If I followed you advice, I'd probably have an (expensive) recharged AC that still didn't work (without jumping it)....and loose the charge when the 'sensor' was removed to be replaced.


Yes I tried a working relay from another position, w/ no luck....first thing I did.

Have you found the 'sensor' on your car yet?

 

Just trying to help. Your diagnostic procedure just didn't match the symptoms in my opinion. Hopefully you can get it working.

 

The older V70's had 2 switches (hi & lo, 2 prong) right in the engine bay that you could easily jump to see if they are keeping the AC from coming on. The second thing people usually try after the relay.

The redesigned 2001's have a inaccessible 3 prong 'sensor' hidden between the radiator & front bumper you can't even see....and who knows how to troubleshoot it?

A incredibly stupid design!!!


So I tried adding some coolant to see if that would trip the 'sensor'....seeing you CAN'T EVEN SEE it to diagnose it electrically!

That didn't work....in fact it overcharged the system & blew a line.
Pretty easy to understand.


All because of that STUPID....inaccessible....redesigned....hidden.... 'sensor'.


p.s. It would cost more to have the AC fixed, that I paid for this car!
And of course the Volvo had a TERRIBLE ventilation system, so I am dying here in the worse heat wave I can remember!!!

 

According to some recent posts I've seen, up to the year 2000, the V70 didn't even HAVE a high side service port to measure the high side pressure. You had to use Vida/Dice if you wanted that information.

Your concern is that the pressure sensor in that very difficult to access location is bad right? Well, I'm guessing that they didn't REMOVE the ability to access the high side reading from the scanner in 2001, which I'm guessing is provided by that sensor. Thus, a way to check it out is to hook up an A/C gauge set to the high side service port, and use the reading put out by the scanner to see if the readings jive. If massively different, wouldn't that suggest the sensor is bad...without having to access the sensor unnecessarily?

Of course, not everyone has Vida/Dice. I picked it up to use for these kinds of things. I've been meaning to hook it up to my 2002 to see if I can access that measurement.

 

Good idea....but see how complicated (& expensive) the Volvo engineers unnecessarily made it?

And my local dealer charges like it's a Rolls Royce now!
Seems the good (serviceable) Volvos were all made last century....and they know it!


I fixed/replaced the water pump, timing belt, 2 CEL's & a (oversized) battery myself after getting it....but I doubt I will ever get this STUPID (expensive) AC fixed.


Also I'd love to switch off the (always ON) headlights, but the (STUPID) engineers removed that switch too!
(the dealer want's $350 to turn them off)

 

Sounds like you really ought to just sell this one and go back to an older Volvo :-) If they last a century like you say, you should be good to go for another 70-80 years right? :-)

 

I can see where not on the same page again....I said the ones FROM the last century (before the 2000's) were easier to work on.

And I just did the timing & pump....good to about 350k miles on this one.

 

Just hooked up my Vida/Dice. Yep, you can access the A/C high side pressure that way (and a WHOLE lot of other stuff). It was about 20 psi lower than my gauge, but still in the ballpark.

 

Thanks for the info. Although I don't have a Vida/Dice (and my local dealer wants $150-200 just to hook one up....PLUS any diagnostic activity!).

But in my state (Masschusetts) we just passed a law that manufacturers/dealers have to make all car/repair info available to the public.

 

For that much, you could buy the Chinese knockoff of Vida/Dice. Can't do major programming operations with it, but for diagnostics, it's nice to have access to the information the car's computer is using.

 

Hi, sorry for pulling up an old thread.....

I am in the process of putting my old air-con back into service.... 96' 850 2.5 20v GLT. Air con dead on purchase in 09' . Been gradually 'rolling restore'' type thing. Finally got to the air-con!

The clutch will not engage on the compressor. The clutch gap was 0.8. I've 'wired' it and it is now 0.3. Spot on, but still not engaging . I have checked gas and it is empty. So no gas it will not engage due to the pressure trinary switch?

A re-gas here is 99€ . This is a suck out old gas, vacuum 15 mins leak test, then slow recharge to correct pressure.

Before I 'comimit' would prefer to confirm the clutch will engage by jumping the relay. Can anyone confirm which terminals to 'jump' on the relay please?