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1997 Chevy Silverado AC problems Pages: 12

marantzman on Wed July 08, 2015 5:29 PM User is offline

Year: 1997
Make: Chevrolet
Model: Silverado 1500
Engine Size: 5.7 L
Refrigerant Type: r134

Hi everybody.

A friend of mine has a 97 Silverado (70,000 miles) that is losing freon.
I put a cheapie gauge on it and it showed 0. So I put 1 small can of freon in. After just a few seconds of filling,the compressor kicks on and it starts to cool. She just had the one can so I stopped.

She drove the truck that same day and had fairly cold air. A day or 2 later,she said the AC had quit.
I put the gauge back on it and it showed 0.
Obviously she has a leak somewhere.
While looking under the hood,I notice the low pressure cycling switch on the accumulator is greasy looking,both the switch itself and wiring. Could this be a possible location for her leak?

Any suggestions on what I should do next? Put 1 can of freon in with some dye? I would hate to fill it completely just to have it all leak out. I'm trying to help an elderly person with a fixed income. If this is something I can help with,I'll be more than happy to do it.
With that being said,I do know when I get in over my head and it's time to take it to a pro

Fast forward: Just to update this.
I finally get back to the truck yesterday.
I replaced the dirty cycling switch on the accumulator and put 1 12oz can of r134 with UV dye.

The low pressure read 0 when I started. After I began putting the can of 134 w/dye in,the clutch engages and the truck blows cold air.
Since I figured it would leak out anyway,I didn't add anymore 134.
I didn't get back to look at it with a light after dark last night.

But I did drop by today to find out the truck is back to blowing nothing but hot air again.
But the difference this time is ............... The compressor is cycling on/off,on/off,etc,etc Yesterday it wouldn't even do that until I added the 134 w/dye
Any thoughts ?
Thank You

mk378 on Wed July 08, 2015 5:35 PM User is offline

I'm surprised you get any cooling from just one can.

Rapid cycling will occur when undercharged though not completely empty. So there still is a leak-- a rather large one. You may be able to find it (cheaply) with soapy water applied to components and connections and look for bubbles. GM compressor shaft seals are also prone to leak. Look for oil and dye in the clutch and pulley area. It may even have slung up onto the underside of the hood.

1wheeler1 on Wed July 08, 2015 5:56 PM User is offlineView users profile

Long shot but I've also read that the high and low side ports can start leaking especially the high if it has the rubber ball valve.
I've seen some Schrader valves keep bubbling after disconnecting the filling hose and snapping it on and off again can sometimes make it quit.

As far as leak detection kids bubble solution works or google for the dishsoap and corn syrup or glycerin recipe/ratio.

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“I’m so thankful I had a childhood before technology took over”

GM Tech on Wed July 08, 2015 6:02 PM User is offline

Compressor belly leaker comes to mind- ball valves will leak, but not if the plastic caps are on tight.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

marantzman on Wed July 08, 2015 6:08 PM User is offline

mk378,

I only put the 1 can to see if I could find the leak for her.Didn't won't to waste her money .
I was surprised that the truck put out fairly cold air with just the 1 can. Don't get me wrong,It wasn't ice cold by any means but it was enough to feel rather cool.

I was surprised that the truck blows really hot air the very next day.I was hoping that the clutch cycling switch I replaced may have been her leak but since the the truck has gone back to blowing hot air After I replaced it,I guess not.

Maybe I'll be able to go over tonight with the light and check things out in the dark.

P:S: I told her before I ever went to look at the truck that the compressor being bad is certainly a possibility for a truck of this age.

Great Forum guys!!

marantzman on Thu July 09, 2015 12:27 PM User is offline

UPDATE: OK guys.
I was able to go by last night and check with the UV Light.
My first look was at the compressor. Bingo! Fluorescent green was easily seen.
I shined the light everywhere else I knew to look and nothing else showed up.
I was kind of expecting a seal leak,not actually leaking at the seams of the compressor.
Anyway,now I can tell her where the leak is.
Just to save her some money,I suppose I could replace the compressor for her and then let her carry it to a shop to get a vacuum/recharge.
Thanks everybody!

GM Tech on Thu July 09, 2015 2:34 PM User is offline

The shaft seals don't leak on those 96 and up model HT-6s because they switched to double lip seals in early 96 Model Year- Belly leakers are the big issue...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

marantzman on Thu July 09, 2015 7:16 PM User is offline

I wasn't aware of that GM Tech.
This compressor must have a bad belly leak.

After finding out I could rent a vacuum pump and a set of gauges,I'm seriously considering doing the job for her.
I don't see anything about replacing this particular compressor that looks too hard.
Replacing the accumulator should be an easy job,I think.
Replacing the orifice tube could be a challenge because I'm not too sure where it's at on this truck.
I assume I would have to add oil to the new compressor? Add some oil to new accumulator? I'll have to learn more about that.
If I feel the job is above me,I won't hesitate to stop.

mk378 on Thu July 09, 2015 11:16 PM User is offline

Main issue with replacing accumulators is that the line nuts sometimes get corroded together and won't unscrew. This can lead to breaking the evaporator pipe and ending up replacing evaporator, which is a major job. Since the system is empty now anyway you can try to unscrew and see if it is going to be a problem.

Really in a case of a simple leak like this you don't have to replace anything other than the compressor, though a new accumulator is advisable after so many years and being leaked down to zero can let water in. The orifice tube should be in the condenser outlet. Look for a place in the high side line that has dimples in the side of the line about 3 inches downstream of a connection fitting. The orifice tube will be in there.

marantzman on Fri July 10, 2015 12:16 AM User is offline

Thanks for the heads up mk378.
I certainly don't want to mess up the evaporator pipe.

Someone had mentioned the orifice tube on this model truck might be accessible after removing the grill or maybe the parking light assembly on the passenger side.
I'll give it a look tomorrow if I can.

Like you said,the system is empty now so I'll also try to see just how tight the nuts on the accumulator are while I'm there.

Thank you for sharing your knowledge and experience!

marantzman on Fri July 10, 2015 1:56 PM User is offline

Quote
Originally posted by: mk378
Main issue with replacing accumulators is that the line nuts sometimes get corroded together and won't unscrew. This can lead to breaking the evaporator pipe and ending up replacing evaporator, which is a major job. Since the system is empty now anyway you can try to unscrew and see if it is going to be a problem.



Really in a case of a simple leak like this you don't have to replace anything other than the compressor, though a new accumulator is advisable after so many years and being leaked down to zero can let water in. The orifice tube should be in the condenser outlet. Look for a place in the high side line that has dimples in the side of the line about 3 inches downstream of a connection fitting. The orifice tube will be in there.

Well,I took your advice and I was able to break the nuts free on the accumulator.They were tight but luckily I was able to free them without damage to anything.

I found the orifice tube behind the passenger side parking light assembly.The nut on the line was very tight as well but I managed to remove it without damage to anything.

I'm thinking I might remove the orifice tube with some needle nose pliers
but will I need a special tool to put it back in without messing it up.

I'll just hold off on that until someone with experience advises me on that.

mk378 on Fri July 10, 2015 3:04 PM User is offline

Tubes just push in. Pressure from the compressor will hold them in place in any case.

Don't leave connections open while you're waiting for parts, put them back together moderately tight to seal up the line and avoid contamination.

TRB on Fri July 10, 2015 4:42 PM User is offlineView users profile

PS: Make sure the OT goes back in the correct direction.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

marantzman on Fri July 10, 2015 6:14 PM User is offline

Quote
Originally posted by: mk378
Tubes just push in. Pressure from the compressor will hold them in place in any case.



Don't leave connections open while you're waiting for parts, put them back together moderately tight to seal up the line and avoid contamination.

I left the orifice tube out but I did snug the line back fairly tight.She is not driving the truck until I'm through.

The reason I ask about installing a new orifice tube was because I wasn't sure if it had to go so far to seat or something.I was afraid I might damage the new one by pushing too hard or something.As you can already tell,this is the first orifice tube I've ever replaced.

@ TRB Thanks for the advice. On this particular one,it looks pretty obvious to me the correct way to put it back in. I will definitely put the new one back in the same direction as the OE that I removed.

Next question guys........just because I have always been a GM guy,I recommended to her that we put a NEW AC Delco Compressor back on the truck. She is going to leave that decision to me.

What do you guys think? A good choice? Other brands? I'm all ears.

Also,thank you to everybody that has taken the time to respond.I do appreciate it!

HECAT on Fri July 10, 2015 9:57 PM User is offline

That brand has not been part of GM for a long time. If its not OE GM; I would order one from this site's sponsor above. Never know what you are going to get in the box today.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

marantzman on Wed July 22, 2015 9:27 PM User is offline

UPDATE OK guys,we got the parts and everything is done except pulling the vacuum.
I rented the vacuum pump and gauges at Autozone.
Here is my problem. It only pumps down to 25 in. I'm stuck and don't really know what to do.
I know 25 isn't enough.
Any thought would be appreciated.

GM Tech on Wed July 22, 2015 10:16 PM User is offline

Gage calibrated? 25 might be 29 - try pulling a vacuum on just the gage set- not hooked to vehicle- see what you get.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

marantzman on Thu July 23, 2015 12:10 AM User is offline

Quote
Originally posted by: GM Tech
Gage calibrated? 25 might be 29 - try pulling a vacuum on just the gage set- not hooked to vehicle- see what you get.

Thanks GM Tech, I'll give that a try.
The gauges and vacuum pump are loaners from Autozone.
Calibrated? I don't have a clue.
The needles are on Zero before I start.
The first time I hooked the pump up today,I didn't see a vacuum of any kind,so I removed the yellow hose from the pump just to make sure the pump was sucking.
With no hose on the pump,I turned it on and held my finger over the hole to feel if the pump was actually sucking. It was.
I then put the hose back on,turned the pump back on and got a vacuum down to 25. Why I got nothing the first time I hooked it up is still a mystery to me.

marantzman on Thu July 23, 2015 1:43 AM User is offline

GM Tech, I took your helpful advice and hooked the pump to the manifold gauge set and sure enough the gauge went right to 29in.
I'm almost afraid to ask but does this mean I have another leak somewhere.
I thought sure by replacing the belly leaking compressor would have stopped the leaks.

I want to mention this to you. Although I only got the reading of 25in vacuum today,I turned the pump off then went in to eat supper,came back out(30 minutes) later. The gauge reading was still 25. I thought maybe that was a sign I didn't have a leak.

But now that I see the gauge actually go to 29 while hooked to just the manifold itself,it makes me wonder.

marantzman on Thu July 23, 2015 3:44 PM User is offline

marantzman on Thu July 23, 2015 4:00 PM User is offline

OK fellows,here is what I noticed today.
It may have been like this yesterday and I just missed it. The low pressure manifold gauge is set 1lb without the gauges even hooked up. Not good. I called Autozone but no could tell me if the screw head I see inside the gauge is to calibrate it or if it is just a screw to secure the gauge faceplate. They will gladly swap it out for me. The closest AZ is several miles away and I don't have the time to go now.

Now on to the readings...........IF I screw the yellow hose to the manifold very hand tight,the vacuum reading is nil, nada,nothing,zero.But if I back it off a thread or so it starts pulling a vacuum of damn near 28in.If not it's a high 27.Anyone encounter that before? Why would I have to putz around with that to get a vacuum?
If the stupid low pressure gauge was set at zerolike it should be,I would feel OK with this.

After a 2 hour vacuum,I closed the manifold gauges,then shut off the vacuum pump. It is holding the same reading I had.It's been 1 hour and 20 minutes.I'll leave it hooked up for awhile longer.

AC_Doc on Thu July 23, 2015 5:31 PM User is offline



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Sometimes you must accept things at faith value!

AC_Doc on Thu July 23, 2015 5:39 PM User is offline

Quote
called Autozone but no could tell me if the screw head I see inside the gauge is to calibrate it or if it is just a screw to secure the gauge faceplate.
The single screw near the zero stop for the gauge is a "zero-set" adjustment.

Quote
IF I screw the yellow hose to the manifold very hand tight, the vacuum reading is nil, nada,nothing,zero.But if I back it off a thread or so it starts pulling a vacuum of damn near 28in.
The rubber gasket inside the yellow hose fitting is squashed and worn out! Whatever it takes to get the remnants of the rubber to seal.




Quote
After a 2 hour vacuum,I closed the manifold gauges,then shut off the vacuum pump. It is holding the same reading I had.It's been 1 hour and 20 minutes.I'll leave it hooked up for awhile longer.
If the pump pulls 29" and the gauge is out of cal, I'd say that whatever vacuum was pulled and held that long, the system is good to go.

Adjust the low side gauge when the set is not hooked up to anything if you want to. Running pressures however, aren't going to need to be within 1 psi.

Ac_Doc


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Sometimes you must accept things at faith value!

marantzman on Thu July 23, 2015 9:12 PM User is offline

Thanks AC Doc.
After experimenting with the yellow hose,I thought about the seal maybe being messed up but didn't really know for sure.I was kind of flustered about it LOL.

Late this afternoon I removed the gauges and pump.It was holding the same reading.It was hooked up for several hours so I am hoping there are no leaks but as I understand it,just because something doesn't leak under a vacuum doesn't necessarily mean it will be leak free under pressure. I actually did see a very,very, faint trace of dye on the hose assembly block. Just because of it's age alone,I will probably just replace it as well.


wptski on Fri July 24, 2015 8:59 AM User is offline

Quote
Originally posted by: marantzman
Thanks AC Doc.

After experimenting with the yellow hose,I thought about the seal maybe being messed up but didn't really know for sure.I was kind of flustered about it LOL.

Late this afternoon I removed the gauges and pump.It was holding the same reading.It was hooked up for several hours so I am hoping there are no leaks but as I understand it,just because something doesn't leak under a vacuum doesn't necessarily mean it will be leak free under pressure. I actually did see a very,very, faint trace of dye on the hose assembly block. Just because of it's age alone,I will probably just replace it as well.
My '90 Buick with new double lip compressor seal held vacuum for days. Driven only a short time at the end of the summer had a puddle of oil on the floor in the spring. They say here new seals can leak till they are broken in. Held vacuum and 150psi of N2 driven lots but still had oil on the floor this spring but much less. Blew a brake line while moving it to get into the loft. Waiting on me when I get the time.

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