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'85 Ford LTD A/C slows car when cycling
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ba_50
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Jul 19, 2008, 8:06 PM
Post #1 of 8
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'85 Ford LTD A/C slows car when cycling
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Hello,
This wagon's A/C was changed to the newer system last January. It was just checked by a College teacher who has working with AC's for years. He said thre wasn't anything wrong with it.
While driving the AC surges about every 8 seconds and I can feel the car slow down and pick up again. It would most likely affect mileage. Is this normal? Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 20, 2008, 1:32 AM
Post #2 of 8
(1821 views)
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Re: '85 Ford LTD A/C slows car when cycling
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Is this the full size LTD or mid sized car with a V6? Actually, A/C was a huge burden on either and many cars of the years that were underpowered to start with. A/C consumes some serious horsepower. Much worse if overcharged which is commonly done by mistake in retrofits to alternative refrigerants.
Take pressures of system while operating. If high side pressure exceeds 2.2 times the ambient temp in Fahrenheit it's working hard. If much more than that it's a problem that needs correcting,
T
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brbettge
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Jul 20, 2008, 3:24 AM
Post #3 of 8
(1819 views)
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Re: '85 Ford LTD A/C slows car when cycling
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Just a thought to add to Tom's answer concerning wrong charge. The general rule of thumb when retrofitting a system from R12 to R134A--- when charging the system with R134A use ONLY 80 - 85% of the recommended R12 charge. In other words if 1lb of R12 is called for..use only .85lbs of R134A. AND, do not worry about "bubbles" in a site glass - R134A will show bubbles normally.
(This post was edited by brbettge on Jul 20, 2008, 3:36 AM)
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ba_50
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Jul 20, 2008, 4:23 AM
Post #4 of 8
(1816 views)
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Re: '85 Ford LTD A/C slows car when cycling
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It is a mid size with a V6. There is a tag saying 1.19 maximum on R12.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 20, 2008, 5:24 AM
Post #5 of 8
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Re: '85 Ford LTD A/C slows car when cycling
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When it was new a (they can be wrong) chart I have list 2.5 pounds of R-12. The 1.19 might be a sticker placed by the original for what is used for a replacement with different refrigerants and some newer parts requiring a much lower weight of charge.
Of interest - do you know what refrigerant was used? 134a would be the common for retrofits. There are other that are difficult to exact the proper charge or I think more so than 134a.
You would notice the power loss of A/C on any but not to an extreme and this on/off you notice suggests something isn't quite right. The engine should compensate for the load at least at idle you shouldn't notice much. This system cycles when either low pressure is at a cut off point (normal for many conditions) or with a high pressure side cut out installed with the retrofit it would cut compressor off at extreme high pressure which could happen at some extremes and be normal but not many.
The questions are....... What refrigerant is used, what is the high pressure, is it cooling well now and is the compressor fairly quiet? They make some noise but if it has a knocking type sound or you can see the belt struggle with proper belt tension it's in need of checking out now,
T
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ba_50
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Jul 20, 2008, 9:52 AM
Post #6 of 8
(1812 views)
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Re: '85 Ford LTD A/C slows car when cycling
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Tom,
The first mechanic said it was low on 134a and was leaking under the dash. He put more in. It cycled constantly. Took it back later and he said it needed more. We passed. Probably a ripoff or he didn't know what he was doing. General mechanic.
The College auto and AC instructor told us everything worked fine.
It gets cold inside. If I'm listening under the hood it makes a loud click. I didn't notice the click so much while driving. The motor speeds up and slows down with the compressor going on and off.
I don't have a pressure guage.
The R12 pressure was the 1.19#
Sounds like I should try another mechanic.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 20, 2008, 5:36 PM
Post #7 of 8
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Re: '85 Ford LTD A/C slows car when cycling
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Quote:
I don't have a pressure guage.
The R12 pressure was the 1.19#
_______________________________
That's a weight not a pressure - perhaps in Kgs.
No matter for now. The cycling is normal in certain conditions. Just wrecklessly adding refrigerant is not in the protocol.
There is a low pressure cut out switch that would cylcle the compressor off - pretty much when the system has accomplished all it can with blowing enough cold if so it stops so it doesn't ice up - that part could be normal.
It would also cut out when low on charge or low side dripped below about 25lbs at a switch that's adjustable on this car. If it cuts out too high it could be annoying at times and you can feel the load of A/C on and off which is what it's doing. The clutch on the compressor does make an audible noise. When all is newer it's not very loud but can be heard.
Without operting pressures taken and temps noted there isn't much I can suggest??
Back to your first post that it is using more fuel possibly with A/C use the answer is probably yes as it's a load on the car. It can be argued that at highway speeds A/C use may offset drag of having windows open and MPG difference could be marginal.
Again - with pressure taken it could be determined if there was something to fix or adjust with the charge weight of the system.
As far as the dash unit (evaporator) leaking it would have to be professionally checked with a sniffer or you could test the water A/C normally drips to the ground for evidence of oils and perhaps dye that might be installed.
Systems will leak some especially at this age it might not be unusual to need a periodic boost - but with known pressures observed. If and when a leak is too fast it calls for the fix of it. Evaporators would be about the most expensive of the components to replace being labor intensive. If slow enough you might just put up with knowlegable boosting if it can last a season,
T
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ba_50
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Jul 24, 2008, 4:28 AM
Post #8 of 8
(1799 views)
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Re: '85 Ford LTD A/C slows car when cycling
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Tom,
Thanks for all the information. I might get the weight and the adjustable switch adjusted sometime. I was tire the last time I drove it 50 miles and didn't really notice it that day or something changed.
I went back and looked at a previous post and your last statement was about using slime in tires. We tried Simonizes version and it worked in 1 out of 3 boat and lawn tractor tires. The salesman at Walmart said it was guaranteed and to bring it back if it didn't work. Walmart wouldn't give a refund at the first two stores but the third one did.
Thanks again. Bob
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