ConcoursMustang Forums
1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year => 1964 1/2 - 1965 => Topic started by: rocket289k on June 07, 2013, 09:25:10 PM
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Hi Guys,
I just fired up my rebuilt '65 Factory AC system. The compressor been completely rebuilt (new seals and bearings) and the whole system was overhauled so I could use 134a refrigerant. The unit blows nice and cold but has a terrible vibration. It's fine at idle but around 1,500 - 2,000 RPM it vibrates so badly the car shakes. If you turn the unit off and let it free wheel on the clutch it's completely fine. Anyone have any thoughts as to the issue?
PS - I'm utilizing the additional idler pulley so this isn't a case of belt slap and vibration that plagued the early AC units.
Regards,
Ron
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Sounds like a bad rebuild of the compressor. Maybe acquire another to try out.
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I rebuilt mine myself, but I am sorry, I didn't take many pictures and I don't have a shot of what I am about to say.
It seems like one part had a counterweight made into it and it sounds like THAT part was put on 180 degrees out?
Either that or 2 piston/connecting rods that are not weight-matched, or a bent crankshaft.
Of course that is assuming that yours has good bearings installed.
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I rebuilt mine myself, but I am sorry, I didn't take many pictures and I don't have a shot of what I am about to say.
It seems like one part had a counterweight made into it and it sounds like THAT part was put on 180 degrees out?
Either that or 2 piston/connecting rods that are not weight-matched, or a bent crankshaft.
Of course that is assuming that yours has good bearings installed.
Thanks Bryan - I didn't do the rebuild myself. I'll have to check with the mechanic that did that for me. Thanks for the info. The bearings were replaced with brand new ones. The counter-weight sounds like the most logical explanation at this point. We'll have to do some investigating when we tear it down.
Regards,
Ron
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Before you tear apart anything, consider changing the tension on the belt that run the compressor. Just move the idler a bit and make the belt tighter or more loose and see if your vibration changes. Just something that has worked sometimes and will not cost you a dime to check out.
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Before you tear apart anything, consider changing the tension on the belt that run the compressor. Just move the idler a bit and make the belt tighter or more loose and see if your vibration changes. Just something that has worked sometimes and will not cost you a dime to check out.
Hi John,
Unfortunately, what I'm experiencing isn't the typical "growling, vibration" belt slap situation that these early AC systems suffered from. I also have the "non-adjustable idler pulley" installed. 1965 and 1966 Mustang suffered from a condition known as "belt slap" due to the A/C compressor belt vibrating and humming due the long travel from the compressor to the crankshaft pulley (on the driver's side of the engine). This was fixed in 1967 by a non-adjustable idler available for 1965-66 cars through local dealers. The vibration can be felt in the steering wheel, pedals and floorboard and a low pitch rumble accompanies the vibration. This condition is usually noticeable at or just above idle.
My compressor is nice and quiet at idle but once you raise the RPM of the engine to 1,500 - 2,000 RPM the car shakes so badly with the AC compressor running it feels like the car is going to come apart. So Bryan's suggestion of the counterweight being installed 180 degrees out intrigues me given the severity of the vibration.
Regards,
Ron
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Is it possibly overcharged with refrigerant?
Do you have all the bracketry correct, including the one to the rear of the intake manifold?
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Is it possibly overcharged with refrigerant?
Do you have all the bracketry correct, including the one to the rear of the intake manifold?
All of the brackets are correctly tightened (including the vibration bar that attaches to the intake manifold). Regarding being overcharged. I believe that was checked already but I'll have to confirm that.
Ron
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Up from the dead! I sure wish this problem was solved. I'm having the exact problem, compressor vibrates like a paint shaker from about 1600-1900 rpm. Above and below that are fine.
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Sounds like a bad rebuild of the compressor. Maybe acquire another to try out.
+1
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+1
Ultimately, I acquired a rebuilt compressor to solve my problem. Once I installed the new compressor the difference was night and day. In my case the original compressor was vibrating so badly the car was shaking (clearly not good).
As a side note, I didn't tear down my original compressor to determine the root cause of the problem so I do not know why it was vibrating so badly.
Regards,
Ron
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Ultimately, I acquired a rebuilt compressor to solve my problem. Once I installed the new compressor the difference was night and day. In my case the original compressor was vibrating so badly the car was shaking (clearly not good).
As a side note, I didn't tear down my original compressor to determine the root cause of the problem so I do not know why it was vibrating so badly.
Regards,
Ron
Good to read you got the problem taken care of . It would be nice to know what the cause was but sometimes you have to weigh the value of determining the root cause vs. a replacement to solve the problem quickly . Less stress and more time for car enjoyment are valuable commodities. Some will not rest until they figure it out no matter how much time and money it takes . Others just want to do what it takes to get it working right and be done with it. Everyone is different . Each of us has to decide which is best for our individual situation.
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Good to read you got the problem taken care of . It would be nice to know what the cause was but sometimes you have to weigh the value of determining the root cause vs. a replacement to solve the problem quickly . Less stress and more time for car enjoyment are valuable commodities. Some will not rest until they figure it out no matter how much time and money it takes . Others just want to do what it takes to get it working right and be done with it. Everyone is different . Each of us has to decide which is best for our individual situation.
Given the recent post, I wanted to provide an update to how things turned out for me.
Completely agree with your post Bob. In my case the compressor issue occurred right towards the end of my restoration and a planned 700 mile roadtrip in the car. Ergo the priority was to get the AC working and worry about the other compressor later. At some point I'll crack open the original compressor to finally get to the bottom of the issue (it's on the list), but I just haven't made the time to do so. The defective compressor was the factory original (as best as I could determine). The unit hadn't been used in at least 15 years prior to the rebuild. The rebuild seemed to go well - the compressor turned freely prior to the rebuild and the bore was in good shape so it was a fairly straightforward rebuild involving seals and new bearings. Clearly we missed something OR there was an error reassembling things. I'll definitely post another update when this job makes it to the top of the list.
Regards,
Ron
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Good updates all, Thanks! The additional pulley didn't help mine either, much. Instead of big belt slap I get two smaller sections of vibrating belt. The compressor still shakes the car a just over idle. I guess a rebuild might by my next step too.
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If one of the reed valves breaks or looses seal it will make for a bumpy ride - acts like imbalance.
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I am a licensed AC guy but it's been a while since I worked on cars but what I do remember is that rebuilding a compressor is hit and miss, parts or lack of good ones is not easily identifiable even to a trained eye. I installed new ones only, comebacks are a terrible loser for the shop and for the customer.
Coils and fans inside and out need to be good and a hard 1 hour or longer vacuum pull is important. Running the AC every 2 weeks is advisable because water droplets are inside the system even with a good vacuum pull and water mixes with R-12 to form an acid. It sits in one spot and starts to eat a hole in the metal, so running it stirs it up so it ends up in a different spot.
Refrigerant needs to be weighed in to specs but R134 requires superheat since there is no Ford Spec and develops higher pressures at higher ambient temperatures, I would opt for a R-12 substitute instead of R134A of which use scroll compressors which can handle the pressures and even liquid slugging which will damage a piston compressor.
Correction: R134 requires sub-cooling to measure in the correct amount of refrigerant but even then it's better to weigh it in if the specs are available. The problem is winter when AC is used with the defrost cycle, although I don't know if mustangs do this automatically. Newer cars activate the AC and the heater to dry the warm air of moisture. A undercharge or overcharge when the condenser is cold, for example below freezing, can damage the compressor. There should be a temperature sender at the condenser to cut it off until the radiator warms it up. Using R134 as a retro fit requires a AC engineer and a testing program to determine the proper amount of refrigerant. There are three components to R134 and they leak at different rates which is why it's not advisable to top off such a system. If it's low on refrigerant then evacuate it on a pump down and weigh in a fresh batch which is what I do on my suburban. It has a slow leak that I don't want to deal with so every two years I refresh the system with 3 pounds.
The worst thing is when the return line or low side to the compressor line ices up which indicates it's changing state from a vapor to a liquid since it's removing heat then it could enter the compressor as a liquid and destroy the compressor. This is why a undercharged system is just as bad or worse than an overcharged system.
Here is a good tutorial if anyone is interested.
http://proaviation.com/wp-content/uploads/2014/01/ConversionAir-brochure-R134a-pres.pdf