Common place for tiny A/C leak in 1995 K1500?

I paid the local repair shop to find a freon leak. The system cools well after I charged it but in about 2 weeks of on/off driving it gets less cold and then eventually loses enough pressure that compressor won't cycle. They SAID they put in dye and recharged the system. Asked me to bring it back when it wasn't blowing cold anymore. Due to unexpected (weeks) of sitting in 2 transmission shops I just got it back and compressor won't go on. I used blacklight and looked everywhere and could not find any traces of dye, even in the low pressure fill port. I brought it back to them and after a day they called me and said that they could see every joint and fitting and could not find any dye. They had no idea what to do next. They suggested that maybe someone washed the engine bay and washed the dye off. I assured them that no one washed the engine bay.

I have to believe if they said they put dye in that they probably did. The tech wondered if maybe the truck didn't get driven enough before sitting in the tranny shop so that the dye might not have circulated all the way through? They did not offer to put more dye in as they would have to then pay to recharge the system and I didn't want to pay them twice.

I carefully checked the compressor as I know tiny leaks can occur at seams and connections. I'm starting to wonder if maybe they didn't put any dye in as an oversight?

My plan was to put dye in myself and continue to use it and recharge it adding more dye each time. I would think eventually I would see the dye somewhere!

Where do these leaks like to hide in the 1995 system?

Get the 134 with the fluorescent dye in it , and top it off so you run it and find the leak.
Inspect all the top engine bay. Then also either from underneath and or using a mirror all lines fittings from bottom. Remove fan blower inspect in blower housing evaporator . All connections. Remove the top filler between grill and radiator, thoroughly inspect back of condenser, airflow blows everything toward engine.
And are you using a UV light ? Not just normal sunlight eyeball? That's what I did, and I do to find leaks.

Common leak can start with the shrader valves.

Thanks GTGuy - i did use a black light at the time the only one I had was a bit bulky as it was a fluorescent tube lamp. But I ordered a penlight size UV light. I wondered if the preloaded recharge cans with dye have the same strength or concentration of dye compared to putting 1/4 oz of straight dye in the system. Yes my plan was to recharge with freon that has preloaded dye and even do that a few times if it leaks down.

'remove fan blower' you mean remove the engine cooling fan?

So is there a fitting or source of leak in the cab in the dash? The shop said they don't get involved in pulling dashes but they said all connections or potential leak spots should be visible outside of the dash area.

movie

movietvet said:

Common leak can start with the shrader valves.

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Is there an easy way to test the schrader valve, or just replace them? I imagine when opening the black cap you might hear a rush of air? Or you can jostle the valve like a bike stem valve to see if it leaks?

95Noobie said:

I brought it back to them and after a day they called me and said that they could see every joint and fitting and could not find any dye.

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Did they check the evaporator / evaporator condensate tube for dye?

95Noobie said:

The tech wondered if maybe the truck didn't get driven enough before sitting in the tranny shop so that the dye might not have circulated all the way through?

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If the AC was run for any reasonable period of time, the dye would circulate. It moves with the refrigerant, so it's constantly coursing through the system.

95Noobie said:

Where do these leaks like to hide in the 1995 system?

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The R4 compressor is know to leak (link below) around the various seals.

I already mentioned the evaporator.

A rock ding on the condenser could be another potential leak.

Otherwise: Any fitting, any pressure switch (leak around the switch body) / switch fitting (O-ring), service fitting (ball valve / Schrader valve), hose fittings (check near the ferrule).

95Noobie said:

movie

Is there an easy way to test the schrader valve, or just replace them? I imagine when opening the black cap you might hear a rush of air? Or you can jostle the valve like a bike stem valve to see if it leaks?

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You can over tighten them. They can "whisp" some noise when remove a cap. You can also see dye there but if you add dye to a system, the only way to check for dye leak at the valves is to clean them thoroughly after the recharge. If not, the dye will be a trace after removing the lines/hoses. Any time I have emptied a system, I replaced the valves.

movietvet said:

You can over tighten them. They can "whisp" some noise when remove a cap. You can also see dye there but if you add dye to a system, the only way to check for dye leak at the valves is to clean them thoroughly after the recharge. If not, the dye will be a trace after removing the lines/hoses. Any time I have emptied a system, I replaced the valves.

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The parts store had a little bitty screwdriver tool to remove the valves but it looked just like the tool I had at home to remove bike tube valves. I have some new valves so I'll see if I can swap them out and clean good after. It would seem to make sense to do that before adding dye since the system is empty now.

If I was going to put money on where your leak is, it would be the condenser, followed by the compressor itself. In my case, it was both. The condenser sits in front of the radiator and absorbs the impact of every rock that gets shot at the front of your truck by a tractor trailer. And the compressors are known for leaking at the belly. A system that leaks enough to cause the compressor to not turn on every 2 weeks isn't a small leak, so I am surprised that they don't see it.

sneakingfart said:

If I was going to put money on where your leak is, it would be the condenser, followed by the compressor itself. In my case, it was both. The condenser sits in front of the radiator and absorbs the impact of every rock that gets shot at the front of your truck by a tractor trailer. And the compressors are known for leaking at the belly. A system that leaks enough to cause the compressor to not turn on every 2 weeks isn't a small leak, so I am surprised that they don't see it.

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agreed so my first step is going to be to try to inspect in the charge port or even below the schrader valve to see if there is even dye in the system yet.