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1977 Eldorado AC conversion to R134a

Started by Rockne Smith, January 03, 2019, 10:35:56 PM

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Rockne Smith

I recently had my 1977 Eldorado AC converted to R-134a Freon.  It now cools and works fine, but after a few miles the drive belt stretched, loosened, or ??, and would squeal when AC first engaged.  Also at highway speed (50 + mph), you could hear belt slightly squeal about every 30 seconds, indicating compressor clutch was cycling on and off.  I took it back to mechanic who tightened belt and told him about the frequent clutch cycling at speed.  He said there was a "cycling" switch on the firewall part (evaporator ?) that controlled the clutch cycling and was normal.  It seems this could prematurely wear out the clutch, belt and maybe other parts.  Does this sound normal, or should I get another opinion?   

TJ Hopland

I believe on a 77 was the first year for the cycling system so especially with cooler winter temps cycling would be normal.   

What is abnormal is that you are hearing it and the belt is slipping.   Today's belts seem a little more stretchy and are often not quite the same shape as the originals.  A 75-79ish has a slightly wider than average belt and I don't recall people talking about slipping issues.   Slipping on the power steering would be a more common issue if the belt was loose especially in something like a parking lot where you are making tight turns at low speeds.  If you are not having any signs of power steering slipping I would suspect something is wrong in the AC system causing extra drag.

How extensive of a conversion did they do?  Same compressor?  Has this shop done conversions before or recently?  I don't think its a very common thing to have done anymore for an average shop so maybe it wasn't done correctly?

Was the system running recently on R-12 or do you know the last time it had worked?   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Rockne Smith

Thanks for your reply.  Car is in FL and AC now works very well in upper 80s.  Guy who converted it to R-134a has done several over the years.  Compressor clutch and controls worked when I bought it (12 months ago), but unit didn't get cold.  They found compressor had leaks, so rebuilt original unit.  Not sure what else, if anything, they did prior to actually adding R-134a.  I'm not sure if someone before my ownership had made any changes to convert to R-134a.  I think the belt squeal can be controlled with proper tension.  With car running at idle or low revving with AC on and hood up, the compressor clutch stays engaged.  It was only at higher rpm (50+ mph) that you could hear the squeal cycling.  With belt tight, I'll probably not hear any cycling while driving.  I could try increasing rpm to equate to highway speed while parked to see what clutch does.  I normally don't like to rev an engine up that high with no load.  I should probably be happy it's cold and just drive it!     

Scot Minesinger

On the single drive belt ac clutches (68 thru 72 were dual belt), I find a heavy duty NAPA belt (green outer skin) works best to avoid squeals.  Not original looking, but does a nice job on those 73-78 heavy Eldos when the power steering and ac are straining simultaneously.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

Rockne,
It took me a while to sort out the issues with the single belt (74-80) systems.
First of all it seems that several manufacturers and belt numbers  are typically listed for these cars but many are incorrect.  The correct AC/PS belt is one that is 60.54 inches long, 0.50 inches in width and has a 36 degree wedge shape.  MANY of the suggested belts are too narrow and do not ride correctly in the pulley grooves.
Another thing is for what ever the reason, the belts currently available today seem to stretch much more then their ancestors.  This in itself is not necessarily bad, but the way the adjustment is on these it reaches the end of its adjustment travel before the stretched belt is tightened correctly.
What I found helpful is to buy the correct width and angle belts but buy one that is one inch shorter than called for.  It can be a little tough getting it on initially but there will be plenty of adjustment to tighten it correctly after it stretches.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-