A/C System Refill Issues

[hoonk]

Isn't the only reliable way to weigh the refrigerant?

Yes, and pull a good vacuum on the system before adding the exact amount specified. Any air or moisture in the system, possibly introduced though bad/diy charging/checking procedures will cause the system to not cool properly. Even with appropriate pressures showing on gauges, there may contaminates (air/water) in the system that can cause the system to operate poorly. Many times I have simply evacuated and recharged what I thought was a properly charged system and have it cool better afterward.

That's not to say you MIGHT get it right squirting some random amount of r134 with the diy can from the auto parts store. Just please don't use the stuff with leak stop in it - it can/will clog a pro AC machine the next time a machine is used on that car.

Have never seen this cause a reduction in cooling performance but - with home units the first thing the ac tech does is change the air filter - has the cabin air filter been changed recently?

I have seen corroded condensers (from northern/coastal states) cause A/C cooling problems, the fins rot away from salt indigestion and simply can't cool the refrigerant properly.

[cattlecar]

First: The cans with a gauge don't seem to ever tell you that a/c pressures are to be checked with engine speed elevated so the compressor pumping capability is nearly 100% The low side pressure will be high and high side pressure will be lower with engine idling. The pressure difference being reduced between those two upsets expansion valve regulation and reduces evaporation potential of the refrigerant. Regardless, 48F is more than I know is normal vent temp for P2 of that vintage but not by much. I would expect 42 from the vent on a cool day with the controls set properly. "properly" in Volvo terms, standard testing for all most all makes, is fan med hi, temp controls full cold, recirculated air, 5 minutes or so for stabilized interior temps, and windows/doors closed.

That system uses a temp probe reading the air temp off the evaporator maybe 1/2 inch from evaporator. The evaporator temp is monitored by the climate control module and then it will request no compressor over CAN to the ECM which controls compressor relay. Cycling that fast will happen with everything working properly with low fan speed.
That system uses warm air mixing with the door regulating warm air volume control being controlled by an electric motor.

First thing to do is to cycle the temp knobs to full hot, wait 2 min, then cycle them to full cold and wait 2 minutes and then see if vent temps cool down more. The damper motors can get some drift and the CCM knows the position from motor counts, not from a potentiometer reporting current position. If they drift the full range motion of FULL hot and FULL cold end points on control range forces the motors to move doors to the stops and if the positions had deviations from the count derived position then it would be updated. A calibration of sorts would be accomplished by this.
If it cools better after this then it is fixed.

On P2 models, on many makes/models for that matter, if all else is working and it is low on charge there is often vent temp differences caused by evaporator not being consistently cold across entire face due to low charge. When fully charged the evpaorator has enough refrigerant for liquid-vapor change to occur consistently. When low the evaporator warms in an area. Due to air flow the warming will cause vent temp differences that do not necessarily follow the left/right temp zones.

[Reverend]

I replaced my evap and vacuumed the system down, refilled with R134 and I get 38F out of the center vents when it's 100F outside.

Maybe use a cheapo Walmart recharge and see what happens? If it leaks, then it's time to figure out what/where the problem is, fix it and vacuum/recharge.

[AutosDirectFlorida]

AC is the one thing that never seemed worth the time and effort to try to do myself.
We had an account with Tire Kingdom and they'd evac and recharge for less than $100.
We tried the cans on several cars and it was never quite right. (especially when dealing with BMW or MB - very temperamental to AC pressures)
One trip to the shop and done every time....

[Oka]

[hoonk]

I'm not sure what the second picture you posted is illustrating - other than the wrong/not easy way to get the outer part of the compressor clutch off. Maybe it is illustrating holding the compressor to tighten the center clutch bolt.

To get your compressor clutch plate off: Take off the plastic belly pan parts in the way of the compressor from the bottom and measure the gap on the clutch plate with a feeler gauge - I think Spec is .3-.5mm. If above about .8mm you might have the heat failure disengagement problem. If gap is too large and your ac clutch stops engaging when it is hot but engages when it is cold, draw a diagram how the ACC belt is routed and take the ACC belt off, remove the 4 bolts holding the compressor to the engine and pull the compressor down and back just enough to get a 10mm socket on the front of the compressor, remove the center bolt and put a slightly longer one in just a few threads. Using parts from the tool kit in your upper picture - the round aluminum disc with the slots is attached to the front of the compressor with three appropriate bolts, (usually not the ones supplied in the puller kit) - the long bolt in the upper left corner of the tool case is then screwed into the center hole of the aluminum disc pushing against the longer center bolt you installed earlier and pulls the outer hub partially off, you may have to loosen the center bolt and make a second push to get the hub all the way off. Take the existing shims out of the center of the hub and calculate how much you will need to remove to get the gap back to ~.3-.5mm. On older cars you end up removing all of them and the gap may still be too big.

The stolen copy of VIDA you will be using does not have a tutorial - even when it was new with a legal subscription there was no tutorial or help page. Available functions vary from year to year, model to model so you just have to plug it into a car and see what is possible. A cool thing it would do for later years (maybe 2007 and up) is a timeline, a calendar of when codes were stored.

[Oka]

I don't think if any of the three openings is threaded. I have the ordered shims from the dealer, removed everything up to the compressor which is tilted enough to pull the disc. It will not move. Kinda frustrated to go this far for nothing. I could have just used the bread clip or zip tie and call all a day. I have done work in cars in my life; this is one of the most frustrated ones I done. Now am angry that I would have to put all that back to end up using a clip or a tie.

[hoonk]

I don't think if any of the three openings is threaded. I have the ordered shims from the dealer, removed everything up to the compressor which is tilted enough to pull the disc. It will not move. Kinda frustrated to go this far for nothing.

Here is a picture of a clutch hub with the puller attached after removal - I'm not quite sure why you are having a problem - the 3 holes on your hub look like there are threads in them, you just have to figure out what (metric) thread they are and find the correct length bolts to use with a puller. Then install a slightly longer bolt back in the center to have something to push against. You don't need new shims - you will be removing the existing shims to make the gap smaller.


You started this thread over a year ago - and have not described the worn clutch failure, what is the existing clutch gap?

Your complaint is lack of cold air, you said 48 degree output on a 62 degree day. You have mentioned a cycling clutch but have never described worn clutch failure symptoms. Here in the south the symptoms are: AC stops blowing cold when very hot outside (90+) after the car has run for a while, usually first noticed on the hottest days of the year when in stop and go traffic. When checked the clutch is not engaged and there is power going to it. The clutch does not usually reengage until the engine cools down or is turned off for a while. When malfunctioning with the engine running you can usually push the clutch closed (very carefully) with a large screwdriver or pry bar to easily verify there is power going to the clutch when it is not working (repeat - very carefully you are pushing against a spinning clutch!) Then measure the gap and if too large, REMOVING shims MIGHT solve the hot clutch/too large gap clutch failure problem.

The first photo you posted at the beginning of this thread showing low side pressure with the compressor running - looks to be about 33 PSI on the low side - that is normal if the engine is above idle speed. For r12 and r134 the low pressure almost equals the refrigerant temp. You don't want it much lower than that at higher RPMs - the refrigerant will freeze solid in the pipes if it gets too cold.

If the system has the correct volume of refrigerant, you may simply have air in the system making the system not cool as well as it could. Air gets into the system from poor charging techniques, maybe from the DIY charging cans. Or a tech makes a mistake and forgets to bleed the air out of the hoses first.

My suggestion once again -

"check parameters in VIDA and your gauges, then if everything looks good evacuate the system with a good vacuum pump for a minimum of 20 minutes and using good charging techniques install the specified amount of r 134 (.9kg I think)" and see if the ac air temp is cooler.

Also check the condenser to make sure there are still cooling fins between the pipes - I have seen several cars from northern climates that were so corroded that the condensers did not cool the refrigerant enough to produce cold air.

[Oka]

As it is right now, I have given up on removing the disc. Since I could not find out the exact size of bolts I would have needed, the ones I have did not work and the steel rods I created as hooks with the took kit puller did not work either. No doubt the holes are messed up.

The gap I have had is 0.026"/0.65mm. I don't see using a bread clip would do this job. I would have to use wires to close the gaps and move on. The frustrating part is moving back all I removed to get to the compressor. After gaping to a good gauge, I would make sure the R34 is enough and try the AC. If still issues, I would vacuum it and refill.

Thanks for all the information, well appreciated.