850 a/c evap replaced

Hi all,

About a month ago I had the evaporator replaced in my '96 850 (non climate control), by a Volvo dealer (ouch!) in Sydney Australia. It was a big job and I felt they would be able to do it with a lot less trouble than I could. And it was done quickly and professionally.

The old evaporator was definitely leaking, it would lose 10" Hg vacuum over

45 minutes. I kept the old evaporator and checked it under UV light as I had dye in the sytem. There appeared to be many minute spots. Sounds typical. It lasted 9 years.

I hadn't noticed anything unusual until last Friday, which was hot, 35deg C, when I noticed the compressor started cutting in and out at less than 5 second intervals, when I pulled into my garage. The a/c vent temperature seemed to be warmer than usual, so I was suspicious and taking note.

My first thoughts were that it had a leak and was low on refrigerant, and I rang the dealer and have it booked in to be looked at next week.

Saturday morning was cooler, 26deg C. In my garage, (at 1500 rpm) I found that with the internal fan on pos 4 (full) I could get the air temperature down to just above 0 deg C, and the compressor didn't cut in and out rapidly. However later in the day on a run when it got hot again, it started "short cycling" again.

Today I bypassed the "superheat" switch on the compressor, and ran the a/c in the garage again, ambient temperature around 25 deg C. The compressor didn't cut out for some time, not until I closed the windows of the car. The vent temperature dropped to 5 deg C. This seems normal. The low pressure line and receiver/dryer were sweating profusely (and dripping on the floor), but the pipe into the low pressure side of the compressor actually iced up (thinly, I could scratch it off with my fingernail) to within maybe 3mm of the compressor. The compressor body itself around the inlet pipe was cold but not sweating. I don't know if this is normal, any comments? The compressor cycled, but around once in 30 seconds.

When taken for a run with the superheat switch bypassed it behaved as before, short cycling (around 5 seconds on and off). Vent temperature around 10 deg C. Outside around 25 deg C.

I've reconnected the superheat switch as it didn't seem to be making any difference.

It didn't behave like this before the evaporator was replaced, that I can remember. The compressor cutting in and out isn't all that noticeable unless I listen for it when I'm on the road.

I don't think this is correct and my feelings are that it's overcharged rather than leaking. Does anyone have any comments?

Regards Barry

Reply to
Baz
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You need to put gauges on the low/high presure side - then you can diagnose to see what is going on, if they overcharge what normaly happens it that the compressor get damaged by getting liquid instead of gas on the suction side (you cant compress liquid so the valves are damaged) - but put on gauges and messure what is going on

"Baz" skrev i en meddelelse news: snipped-for-privacy@dnews.tpgi.com.au...

Reply to
ena

Thanks for the reply. The 850 doesn't have a high pressure side service point, only low pressure. I've read that the high pressure is measurable from the engine management system (with the right Volvo service equipment), but I haven't seen any sensor for it. Normal procedure I believe is to just measure the correct weight of refrigerant when filling, if you don't have the Volvo service equipement.

I'm aware of the damage that can be caused by liquid getting back into the compressor, thanks for reminding me :-)

It's at the dealer's today, so I'll see what they say. Lets hope there's no damage :-(

regards Barry

temperature

Reply to
Baz

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