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 96 RMW A/C stops blowing after 1 hour

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Haze5736



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Join date : 2016-08-12
Age : 44
Location : East Syracuse, NY

PostSubject: 96 RMW A/C stops blowing after 1 hour   Sun Jul 09, 2017 3:32 pm

I'm trying to troubleshoot my a/c system. Just got back from a road trip and I notice that the a/c almost stops blowing after about one hour of operation. A small amount of air still comes out, with fan on high, but it can't keep up especially when the sun is out. If I shut it off for a while then turn it back on it will function ok for another 30-60 minutes. I saw there is a similar post by Glide-Aways. I did check to see if there was air flow from the floor vents and there was not.

Could a dirty evaporator alone cause it to ice over? When I first got the car it was filled with dog hair, tons of it. Thick, wiry german shepherd hair. Or would it just accelerate the icing up that is caused by some other issue? I have not looked at it yet. That's my next task.

I have a set of a/c gauges so I was able to take the high and low side pressure measurements. The test was done today at 79 degrees F with 60% humidity. The readings were taken with the engine at 2,000 rpm. According to the FSM I should have a max low side of 36 psi and a max high side of 315.

My readings are 30 psi on the low side and the high side fluctuates between 330 and 350 psi. So my low side is a little low and my high side is high. I'm new to working on a/c so not sure if those readings tell me anything definitive.

The other thing I noticed is that when I first took the high side cap off, while the engine was running and already up to operating temp., I could see some bubbles coming from the schrader valve. I can't remember if the a/c was on or off at that point. After I took the gauge coupler off I did not see any more bubbles.

Any pointers on what to do next would be greatly appreciated. Thanks.
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Sun Jul 09, 2017 5:29 pm

You may need a little refrigerant, but the evap core icing up would be my first move. There can be junk in it as well. It is a PITA to get the tray off to check/clean the evap core. NY is not the area I would suspect icing, but I have heard that low refrigerant can cause icing of the evap core.

If you can check for water flow from the pan drain, it could give you an indicator of whether the core is icing or not. A steady flow is good, intermittent/stoppage flow is an indicator of icing.
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Haze5736



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Wed Jul 12, 2017 6:55 am

Should I be concerned with the high side pressure?

Where is the evaporator? The FSM shows an image of the evaporator but nothing to give a point of reference for its location.
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Wed Jul 12, 2017 9:06 am

I reread the first post, and I would be inclined to look at the fan control module. It may be overheating and the IC may be failing. The reason I say this is because the fan is not "blowing" after a time period, and will work again after a rest. The pressures may be within tolerance, but you may need a little refrigerant anyway.

The evaporator is in the HVAC plenum, and can be accessed through the drip pan.
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Rev Bob



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Wed Jul 12, 2017 12:15 pm

""A small amount of air still comes out, with fan on high,""

Sounds like the fan is still running, but the evaporator is iced. Some causes might be: low charge, a clogged evaporator on the air coil side, or a malfunctioning low side pressure switch.
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paart



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Sat Jul 15, 2017 4:28 pm

The other thing I noticed is that when I first took the high side cap off, while the engine was running and already up to operating temp., I could see some bubbles coming from the schrader valve.

The high side port on these vehicles does not use a "schrader" valve. Instead, there a small pressure operated rubber flapper, and they are "troublesome". If you find you need to open the system for repair, I'd plan to replace it.
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Haze5736



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Sun Jul 16, 2017 7:35 am

I added UV dye to the system a little over a week ago. I ran it very little because of an oil leak but last night I was able to see the leaks with a black light. There was a slight amount of dye on the high side port and also a much more noticeable leak at one of the lines attached to the back side of the compressor. I can't remember which line it was so I'll have to go back out with the black light.

I'm going to have the system evacuated so I can perform the repairs but I need some guidance on what to replace.

I'm planning to replace the high side line as suggested. If that is the line leaking at the compressor I'm assuming the new line and seal should fix the leak.

If the leak turns out to be at the other line what is the recommended repair? Is there a seal to replace or would the entire line need replacement? It's the line going to the accumulator.

Is there anything else that I should replace while I have the system open?

Will I need to do anything with oil if I only change out lines and seals or just add refrigerant?

What is the best way to clean off the UV dye so that when I recharge the system I can look for new leaks?

Lastly, can anyone give me a rough idea of what it costs to have the system evacuated?
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Sun Jul 16, 2017 8:01 am

The compressor line includes the line from the accumulator to the compressor, and the line to the condenser. It is one piece It should be the only line attached to the compressor. The line should have a new high side valve on it. If not replace the valve. The line should come with new seals, but you may just have old hard seals, and be able to replace them to fix it. If you are going to replace the just the seals, replace the high side valve valve too.

If it ain't broke don't fix it.

You should be able to add refrigerant and go.

Carb cleaner or brake cleaner should take the dye off.

It cost me about $200 to have the system evacuated and charged. You can buy a vacuum pump for less than that. If you ever anticipate doing it again, the pump will pay for itself. Check Harbor Freight for specials, and use the 20% discount coupon to get the best deal. You can get a free flashlight, multimeter, or other item as a bonus.
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Haze5736



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 7:22 pm

I decided I'm only going to replace what needs replacing. Since the lines themselves are not leaking I am going to replace the seals.

Here's what I'm planning to purchase

1. seal kit
2. orifice tube
3. accumulator
4. high pressure valve

One thing I still don't understand is what, if anything, I'm supposed to do about compressor oil. It's not clear to me if changing the accumulator requires adding oil. I don't understand how to check for the proper amount of oil. I just read through all the a/c posts and I think I need to so something here.
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 8:41 pm

You can drain the accumulator, and replace the amount that you measure. My question is; why change the accumulator?
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Haze5736



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 8:49 pm

Fred Kiehl wrote:
You can drain the accumulator, and replace the amount that you measure. My question is; why change the accumulator?

I saw a couple of posts, can't remember if it was this forum, that said to change it if it has been open to the environment for any length of time or if it is more than 5 or 6 years old. I have to assume mine is over 6 years. I thought I saw a post from someone that quoted a GM recommendation to replace it if over 5 years old and the system is opened for service. I can certainly leave mine in place, the system is still sealed but I want to be 100% sure I'm doing the best job possible and not have to open the system up for a long time.
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 9:10 pm

The accumulator has desiccant in it and if it has absorbed all of the water it can, it is no longer good. The desiccant may come out with the oil. They have been in cars for their entire life, or as long as the AC has been working. I am not sure if the time limit is just to get you to spend money.
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Haze5736



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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 10:02 pm

I'm working on ordering my parts from Rockauto now. They show 2 types of orifice tubes. One is Optional Automatic Adjusting, the other is not. Which one should I order? Thanks.
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Fred Kiehl

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PostSubject: Re: 96 RMW A/C stops blowing after 1 hour   Mon Jul 17, 2017 11:01 pm

I cannot imagine how the orifice tube can adjust. I would go with a stock one.
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