1989 F250 AC Question

[George1]

Good morning. While driving the truck this morning a loud intermittant screech started coming from under the hood. The noise then became steady, very loud. Stopped, kept the engine running, checked a few things then saw a cannister labeled Climatizer and Air Conditioner. Whacked it with palm of my hand, and lo and behold, the noise stopped. AC still works. Is this a sign of impending doom of my AC? Not finding any info on what this thing does. I expect that if I replace the can, I will have to degas the system so I would like to avoid that. I can live with whacking the thing once in awhile as the truck gets only a few hundred miles a year put on it.

Thanks for any responses.

[ctesla]

could just be a gummed up orifice tube in the AC Drier; but you are right, to get to this, you would need to discharge and reclaim (if it is R12 OEM), or bleed and recharge if converted to R134a.. do not have enough knowledge of Ford AC systems (or any for that matter, at 9400ft. elevation) if this will put undo pressure on your higher dollar compressor or not..
usually service centers (pep boys, les schwab, meineke, etc.) start running AC service deals after spring (last week, with the exception of colorado; still two months away)..
this would be a flush and fill, leak check, and usually a new expansion valve (o-tube) for under $100-150 depending upon region, store, and coupon..
you could even ask to have new drier installed at this time for probably under another
$80 or less; $25-40 for component, same or slightly more for labor..
BUT, this is only if you have already converted to the R134..

[George1]

Thanks cTesla. This is narrowing the problem. Appears that this is not a mechanical issue. If one of the tubes is gummed up, does the screeching noise come from gas passing through a restricted opening. So that whacking the top of the filter, some of the gunk shifts. Sounds like that is what you are saying. Don't need to get a huge discussion going here, I am just trying to understand it a bit. Could the noise come from the desiccant being plugged up inside the filter?

[ctesla]

so, AC system does not actually generate/create cold air; it actually scavenges heat and moisture out of air already in the car, and then fan blows over the evaporator which has now had "chilled" from the compressor's hot gases pushed to condenser (ac radiator) where air passing over fins and tubes assist cooling.. so now, the hi-pressure gas returns to a liquid refigerant; then moves into receiver/dryer which hold the dessicants; that pull water vapor out, and then it is ready to move to the low pressure side; thru the orifice tube/expansion valve.. the 'screeching' by your theory (or my guess) would be either water vapor coming in too hot, or o-tube partially blocked so not allowing equalization in the canister; maybe like a teapot whistling and temp and/or pressure..
--again, not an AC specialist; so this is pretty rudimentary- compared to what an AC guy/girl could break it down way better, i'm sure.. and possibly give a better possibility to your anamoly.. GM o-tubes are like .79-4 bucks; but like i said, closed loop system, so as far as i know, you have to drain to swap.. and unless it is done professionally (with reclamation unit), i have always heard you should swap out drier at that time, as humidity can contaminate when you open system, and after you swap the cheap o-tube, you're doing it again in 3months as the rec/dryer is bad..
a jiffy lube or Firestone tech could answer better.. since system is still 'working' as you say, it sounds like hi-press. side still operating, from receiver/o-tube/evap; the lo-side sounds like culprit..
i hope this helps..

[George1]

Really helpful--thanks.

[George1]

AC drier.