Should a/c compressor cycle on/off while driving?

[abscate]

I'll probably just crack the 19 and 22mm on the fat hose and leave the evap connection alone.

The fat hose vents cool cabin air to the ECU box, those two Torx screws are a PITA to remove.

It is possible to wrench the 19 and 22mm connection holding the orfice tube in place but it is tight.

I'll pump it down for a couple of hours when done, no problems with moisture. Brand new drier so any residual moisture will get absorbed

[wheelsup]

Wow you could get your hands in there? I gave up quickly. You must really hate those disconnects!!

Torx to remove the vent hose? Interesting. I just pulled mine off, had some sort of metal clips holding it in place on my 850.

[abscate]

On edit - the below is wrong - see correction downstream

On the ECU hose, two Torx screws into the firewall, then the hose also breaks into two (slip joint) about midway on the 1999. This is also a good opportunity to replace the rubber gasket on this, which I found on the driveway after this repair....



I can get the 22 on the bigger nut which the jams in the space between fender and timing belt cover (tbc)

Now your hand goes over the top, behind the tbc, (aha! I had the turbo baffle off when I did this, which gives you more room!) And i can screw the 19mm down to about 1/2 turn from spec torque. The 19mm will now reach torque using the offset property of the jaw a couple times, not too bad.

Its easier to put the orfice tube in on the bench, though.



I actually assembled this tube with the 19-22mm loose as I thought it would be better to Optimise the orientation after connecting the evaporator and the the frame member joint.

On the turbo baffle - this puppy bolts into the stuff near the exhaust which gets awful hot, so I liberally dosed the bolts with Never Seize after wire brushing them clean.

[wheelsup]

OK it is my belief that the system was undercharged. A couple of notes back and forth between another site and an ac guy who is helping me. I used aftermarket parts and I'm wondering if the items had a much larger capacity than the Volvo OEM stuff. My accumulator is an aftermarket from a large name supplier, so it's possible they make the same size unit and stick the top connections on to make them fit each car.

The other site mentioned that priming the lines often takes a couple ounces out of each can. Also I bled the lines and lost at least 1 oz per can (it comes out quickly). I have now put in three 12 ounce cans minus the amount I am losing per can switching them. Assuming I am losing 3 oz per can, I'm at 27 oz +/- in the system which is very close to OEM system capacity. Noting others have charged up a little higher to prevent excessive cycling...

I found this web site:
http://volvo850wagon.wordpress.com/tag/r-134a/

He mentions the pressures and temps, so I can compare with my own. With his OAT, when it was around 80*F, as was mine, I was seeing 25 PSI on the low side at idle. He charged his to 40 (not saying it's right, but that is where he bought it up to).

After putting in the additional can I'm at 30 psi @ idle. Still cycles at higher RPM, but takes longer. So I think I am still undercharged slightly.

[abscate]

Torx to remove the vent hose? Interesting. I just pulled mine off, had some sort of metal clips holding it in place on my 850.

Wheelsup is right on this one. Im finishing my AC repair today, and, on closer inspection, two metal clips allow separation of the ECU cooling hose without removing the Torx screws.

My aluminum tube was fused together so it never popped out, but after I separated, cleaned and put a little silicone spray, it was much easier. Pix to follow for the visually needy

[abscate]

Well, the followup on the orifice tube story got ugly

Good news is my V70 has been idling for an hour, 82F ambient, 38 PSI on low side, with 32 degrees F delta on the AC at idle. A bit low performance, I would like to see 40F delta

...but its working!!!

Instead of following advice here, I tried 'my way' of installing the orfice tube, and things degraded rapidly.

First, I found a broken orfice tube in my new high pressure side tube - the source of my problems. I put the old one back in and prayed.

I had previously stripped the frame member nut, so I had a SS screw pinning down the high pressure frame member mount (HPFMM), which also houses the Pressostat switch and the

Fooling with the 19mm and 22mm union, I bent the tubes slightly, and, with the clearances being tight as they are, I managed to strip the holddown 6mm hex screw in the HPFMM.
I threaded at 4mm hex/lock nut down, but now I had to thread the High pressure to Condensor hose down past the dryer, connect the high pressure union, and then bolt it in place with access to top and bottom.

It was b***n hard - and I ended up taking wheels advice and breaking both the evap and the drier double Oring tubes with my AC Snap tool. Now Im all the way down to 10 USD per use.

I made a note in the log that if I do AC work again on this car, I will replace the high pressure hose, or at least try and retap that hole.

The slight bend in the AC tubes running back to the evap also reared their ugly head installing that ECU cooling tube - the clearance (Clarance) is very tight and that install was a Charley Foxtrot too.

Upshot - you need all the connections on this puppy in good working order to get these parts in and lined up correctly. Since I had to connect the HPFMM to the condensor hose before mounting, I had the to thread that down below the condensor while lining up the union for the orifice tube - it was about 9.5/10 difficult to thread all that stuff.

As designed, the job would have been simple of course, so I cant fault Volvo for this one.

I now have new EVAP core, all new pressure lines, so compressor and condensor are all that is left old on the entire AC!!

....but it is running, and running cool...



Edit - performance update - at 2000 rpm around town, getting 38F differential, so looking good.

[bavarianstig]

I am having a slightly different issue. Even though my AC does not work, I am not getting any of the diagnostic flashing lights from the control unit.

Normally when you press the AC ON button, the red LED on the "OFF" button disappears and the green LED on the "ON" button lights up. In my case, after pressing the ON button, nothing happens (the OFF button's red LED remains lit). Furthermore, I have the same issue with the recirculate button, as I cannot get it to work either.

However, if I set the blower selector to defrost (windshield/12 oclock position), the "AC ON button" light will finally turn green and I get AC. While on defrost, the air it blows is cold and the compressor engages the clutch at a normal interval (makes me think refrigerant level is ok). Could this be caused by a bad cabin temp sensor?

[abscate]

That seems to point to a bad Control module. It might be worth trying to clean the two switches

[xHeart]

It is one year anniversary of this thread.

I have mildly cold air in the cabin with fan knob at full, temp knobs at cold, AC and Recirc switches ON.
It is 1997 850 NA, no ECC.

At the engine, the clutch cycle is OFF and ON every few seconds.
At the bulkhead/firewall, the narrow line (without sensor) sweats cold. The thicker line with sensor switch is mildly cold.

I turned and pulled the cap off of the low pressure port next to the ECU while engine was hot and idling, it released small amount of green fluid, placed the cap back on, cleaned around it with paper towel.

What steps to take next so the ice cold air is restored?
Maintaining two Volvos, hence looking to order this https://www.amazon.com/Interdynamics-GBM-4-R-134a-Conditioning-Charging/dp/B004QQ8SEY/ref=sr_1_3?ie=UTF8&qid=1401549881&sr=8-3&keywords=r134a+recharge+kits.

...and few cans of something like this https://www.amazon.com/gp/product/B00C4XFMO0/ref=pd_luc_bxgy_01_02_t_lh?ie=UTF8&psc=1

...any suggestions on purchase, better choice?

[jimmy57]

Cycling once car has cooled inside is OK. Cycling in this case would be a 3-10 seconds on and 2-5 seconds off cycle. More rapid cycling and cycling initially before interior has cooled when fan is not on lowest speed would mean you are low on refrigerant.
Since you have an 850 it could be evaporator leak if it has been 5 or more years since an evaporator replacement.
Like one 12-14 ounce can will restore cooling but it might need a little more.