66 Factory A/C Problem
Thread Starter
Instructor
Joined: Aug 2003
Posts: 106
Likes: 4
From: Savannah GA
66 Factory A/C Problem
I have a 1966 coupe w/ a small block and factory air that I have owned a little over 2 years. I drive the car a minimum of once a month, and an average of 40 to 45 miles per month. I always try to run the A/C regardless of outside temp to keep things lubricated.
On my ride last month the belt screeched when I engaged the A/C, and screeched when I accelerated. The A/C was on for about 25 minutes, and blew cold the whole time. When I got back w/ the hood up, A/C engaged, it screeched every time I moved the throttle linkage.
This month I checked the belt tension, loosened it up a bit, and engaged the A/C. Belt screeched immediately and consistently. Turned it off, no screeching. Belt condition is new.
What’s going on here?
On my ride last month the belt screeched when I engaged the A/C, and screeched when I accelerated. The A/C was on for about 25 minutes, and blew cold the whole time. When I got back w/ the hood up, A/C engaged, it screeched every time I moved the throttle linkage.
This month I checked the belt tension, loosened it up a bit, and engaged the A/C. Belt screeched immediately and consistently. Turned it off, no screeching. Belt condition is new.
What’s going on here?
Melting Slicks
Joined: Feb 2006
Posts: 3,125
Likes: 2
From: Park City to SoCal - according to the map it's all down hill. No bad days in Indian Wells, California
Belt screech is usually from loose belt...... so the tension needs to be increased. Even new belts that are loose will screech.
There is a tensioning guideline that says something like - at the longest stretch of belt the distance when pressed down on the belt should be no more than 1/4 inch. Don't quote me, just something I remember.
Also, even if the belt is new it may need some belt dressing. After being used in a hot engine compartment the rubber can dry out a little and be somewhat brittle.
Good luck
There is a tensioning guideline that says something like - at the longest stretch of belt the distance when pressed down on the belt should be no more than 1/4 inch. Don't quote me, just something I remember.
Also, even if the belt is new it may need some belt dressing. After being used in a hot engine compartment the rubber can dry out a little and be somewhat brittle.
Good luck
Thread Starter
Instructor
Joined: Aug 2003
Posts: 106
Likes: 4
From: Savannah GA
My bad. The belt is not "new" - it's been on for about 14 months, maybe 600 miles, and I think the tension has been fine. Just meant that it's in good condition. I think this is more than the belt. Seems like engaging the A/C is now creating a lot more resistance than it did before.
Thanks.
Thanks.
Race Director
Joined: Mar 2002
Posts: 13,646
Likes: 3,595
From: NorCal
Belt screech is usually from loose belt...... so the tension needs to be increased. Even new belts that are loose will screech.
There is a tensioning guideline that says something like - at the longest stretch of belt the distance when pressed down on the belt should be no more than 1/4 inch. Don't quote me, just something I remember.
Also, even if the belt is new it may need some belt dressing. After being used in a hot engine compartment the rubber can dry out a little and be somewhat brittle.
Good luck
There is a tensioning guideline that says something like - at the longest stretch of belt the distance when pressed down on the belt should be no more than 1/4 inch. Don't quote me, just something I remember.
Also, even if the belt is new it may need some belt dressing. After being used in a hot engine compartment the rubber can dry out a little and be somewhat brittle.
Good luck
Probably just a loose belt. I remember the old rule of thumb as no more than 1/2 inch belt deflection.....in any case, tighten the belt until the screeching stops. The belts have been on my factory A/C 67 for about two years, maybe more, with no screeching when I turn on the A/C.
Melting Slicks
Joined: Aug 2004
Posts: 3,078
Likes: 101
From: Riverhead New York
A/C Screech
Most often it is the belt tension that needs to be corrected. Another cause is over charging of the system with too much Freon. Did your problem just appear or did it appear as a result of work being done. What type of Compressor does your car have? The original A-6 is known for its drag effect as it takes a lot to turn it. Are your Pulley's the correct ones? Al W.
Thread Starter
Instructor
Joined: Aug 2003
Posts: 106
Likes: 4
From: Savannah GA
No work on the system since I bought the car. It had been converted to 134 by the previous owner. Compressor is a Frigidaire Model #6550113. Noise just started. No particular "event". I finger check belt tensions when I service the car, and I may be wrong but I did not detect any appreciable difference when I checked it after the noise started.
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Le Mans Master
Joined: Nov 2000
Posts: 7,246
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From: Going too fast over the hill. Iowa
I got a lifetime guarantee belt at Oreilly after going through 2 belts a year for a few years. I also use their belt dressing for pulley traction.
I have a GM belt tension gauge. In order to get the correct tension on a new belt, I have to put a 16 inch tire iron on the compressor. When the tension is set properly using the GM gauge, the belts do not squeal.
Early GM compressor drives used single belt pulleys. Later ones used dual belt pulleys for twice the traction.
I have a GM belt tension gauge. In order to get the correct tension on a new belt, I have to put a 16 inch tire iron on the compressor. When the tension is set properly using the GM gauge, the belts do not squeal.
Early GM compressor drives used single belt pulleys. Later ones used dual belt pulleys for twice the traction.
Tech Contributor
Joined: May 2005
Posts: 15,576
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From: Conroe Texas
Thread Starter
Instructor
Joined: Aug 2003
Posts: 106
Likes: 4
From: Savannah GA
To answer Al's question I've had the car for a little over 2 years, and put slightly over 1,300 miles on it before the problem started. I replaced all the belts in February 2006. The car has a single pulley compressor, and the engine pulleys appear to be correct. It also has power steering.
Judging from the comments above I gave up on the belt tension solution too soon! I'll give that another shot tomorrow, and pick up some belt dressing.
Thanks to all for your input.
Judging from the comments above I gave up on the belt tension solution too soon! I'll give that another shot tomorrow, and pick up some belt dressing.
Thanks to all for your input.
