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  #1  
Old 06-28-2011, 05:15 PM
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Air Conditioning Help

Hello,
About 2 weeks ago when we had our first decently warm day I noticed my truck's AC was not cooling. I finally got around to looking at it this past weekend. The compressor was continually cycling on and off every few seconds.

I have a cheap auto-parts store pressure gauge for the low side of the AC, and I don't know a much about it. I checked the pressure and it seemed low. I added some 134a and got the pressure to read where the charts I have said it should read (about 32 on a 65 degree day) and the compressor then stayed on-- electric fan clutch on and everything. I also added some stuff with red dye in it to see leaks, but couldn't see any. Vent temp about 42 degrees. Now for the past couple days I have driven it in the mornings and it cools nice, but by the afternoon with warmer temps, it's not cooling nearly as much.

Today on my drive home I couldn't get the vent temp below 60 -- way too hot. When I got home, I opened the hood and the compressor is cycling every few seconds again. I checked the pressure, and the pressure is higher than it was before, but looks like it's within the chart specs for the temp today.

I jumped the low pressure switch and it acted the same way.

What do I do at this point? Is it beyond my DIY ability to fix this thing? Do I need to call in a Pro? What else do I check?

Thanks!

Adam
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Old 06-28-2011, 05:17 PM
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You need a UV lamp to see that dye. I'm sure you have a leak somewhere.
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Old 06-29-2011, 02:32 PM
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Ok, let me add a little more to this riddle.

I haven't made any changes since I posted yesterday.

This morning it was about 62 and I checked to see how cold I could get the AC and I got it down to almost 40.

This afternoon it was around 60 and I checked again -- almost 40.

BUT, I stopped to fill up the truck and when I restarted and tried again, I couldn't get it below 60.

So-- what gives...?

Adam
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Old 06-29-2011, 06:25 PM
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Ive been messing around with my a/c and Freon psi for a few days and the best i can get is 40-41 degrees out of the vents. It is a bit hotter here though, im getting these temps with 105-110 outside temps.

Those temps are while moving, im getting 44-45 while idling. I did take off the grill and washed out the condenser fins and that seemed to help get the temps down quicker and keep them closer when not moving.
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  #5  
Old 06-29-2011, 06:28 PM
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Yeah, I'm guessing you have a leak somewhere.
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Old 06-29-2011, 06:34 PM
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Quote:
Originally Posted by 89MustangGX View Post
Ok, let me add a little more to this riddle.

I haven't made any changes since I posted yesterday.

This morning it was about 62 and I checked to see how cold I could get the AC and I got it down to almost 40.

This afternoon it was around 60 and I checked again -- almost 40.

BUT, I stopped to fill up the truck and when I restarted and tried again, I couldn't get it below 60.

So-- what gives...?

Adam
You might check your clutch shim. It might be JUST loose enough that when the engine is warm, it slips just enough to give symptoms like you describe.
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Old 06-29-2011, 07:37 PM
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Quote:
Originally Posted by Evil Eye View Post
You might check your clutch shim. It might be JUST loose enough that when the engine is warm, it slips just enough to give symptoms like you describe.
Can you explain more? How would I check this?

-----

I'm not disputing a leak, but it's strange to me that at 5 years old and 85k miles I am having an AC problem of all things. This really has me scratching my head. I've had vehicles much older than this that never had problems with AC at all, and it doesn't seem to be a common thing.

Thanks for your help...please keep the ideas coming for things I can check without/before taking it to a pro.

I'm thinking I may need to invest in the UV light to check for leaks next...

Adam
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  #8  
Old 06-30-2011, 06:37 AM
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Quote:
Originally Posted by 89MustangGX View Post
Can you explain more? How would I check this?

-----

I'm not disputing a leak, but it's strange to me that at 5 years old and 85k miles I am having an AC problem of all things. This really has me scratching my head. I've had vehicles much older than this that never had problems with AC at all, and it doesn't seem to be a common thing.

Thanks for your help...please keep the ideas coming for things I can check without/before taking it to a pro.

I'm thinking I may need to invest in the UV light to check for leaks next...

Adam
Well, actually these systems leak all the time. Usually from the seals due to non-use. Here's a quote from another forum. Look up A/C Air Gap and you'll find this is somewhat common.

Quote:
Get out your feeler gauges, or your calibrated eyeballs, and determine that the air gap is about .050" to .060" (fifty or sixty thousandths). That's too much! It's supposed to be around .030. But wait! There's no need to replace the compressor and have to re-charge the system. There's a "dirt-cheap" fix!

See the little bolt right in the middle of the compressor shaft? Take it out. You won't be letting any Freon out. Pull the clutch plate straight out. There is one or more "shims" that look like small washers in there, either on the end of the shaft or down in the hole that fits on the shaft. Take off about .030" worth of them and reassemble. Go ahead, use a little blue (NOT green!) Loctite on the bolt as insurance.

Make sure you now have at least .025" of gap. Start the engine and check to insure your problem is gone.
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  #9  
Old 06-30-2011, 04:11 PM
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Quote:
Originally Posted by Evil Eye View Post
Well, actually these systems leak all the time. Usually from the seals due to non-use. Here's a quote from another forum. Look up A/C Air Gap and you'll find this is somewhat common.
I checked the Air Gap by (carefully) pressing on the clutch with the AC on during one of it's off cycles. It didn't grab. I believe this means the air gap is good, as it did continue to cycle on and off.

This is really pretty frustrating. I still don't want to give up on it. I'm thinking maybe I will pick up a manifold tomorrow to try to do some more advanced troubleshooting.

If anyone else has any ideas-- please help!

Adam
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  #10  
Old 06-30-2011, 04:38 PM
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Quote:
Originally Posted by 89MustangGX View Post
Can you explain more? How would I check this?

-----

I'm not disputing a leak, but it's strange to me that at 5 years old and 85k miles I am having an AC problem of all things. This really has me scratching my head. I've had vehicles much older than this that never had problems with AC at all, and it doesn't seem to be a common thing.

Thanks for your help...please keep the ideas coming for things I can check without/before taking it to a pro.

I'm thinking I may need to invest in the UV light to check for leaks next...

Adam
I have seen vehicles with 30k miles leak. O-rings and seals can fail any time. It's possible that you had just enough pressure in the system to make the compressor run. When you are low, the compressor will cycle on and off like that. Go to Walmart and buy a blacklight. They work too. But Autozone probably has little UV penlights that are more convenient.
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