WEIRD HVAC BEHAVIOR ????

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bugdewde

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1995 K2500 Suburban
454 7.4L
with front/rear A/C

I haven't put pressure gauges on the system yet .... Because I suspect electrical at this point.

Here's the 4 weird symptoms encountered so far:

-- Occasionally, the A/C and Recirc buttons do not light up when pushed. No matter how many times I push them. The compressor engages and A/C works, but button doesn't light all the time.
-- Also, occasionally, the a/c stops blowing cold air, like the compressor shuts off. After a short while, cold air again.... with no regard to button light.
-- Occasionally, when on Max setting or with Recirc on, you can hear/feel the fan speed vary from High to Max. .... Intermittently.
-- Sometimes, the clutch will engage/disengage repeatedly. I can shut off the engine, restart, and all is good.... except for the above mentioned issues. .... which only occur intermittently.

Looking for the best place to start troubleshooting.
I've read here that the door motors go bad & also come loose from the doors.
I was just wondering if these symptoms could be due to door/motor issues, dash button/switch issues or charge/pressure issues. ... or maybe all three?

My first plan is to hook my gauges up to check pressures.
Any tips on where to look for solutions?
 

95C1500

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I'm having the same issues as your last two. I have a leak so mine is low on freon causing the short cycling issue. I'm going to evacuate the system and fill it back up. My fan speed issue, I don't know where to start
 

andy396

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First easy and cheap thing to try would be the low pressure cycling switch on the accumulator/dryer. It’s like $15 and can be swapped in the parking lot.
 
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95C1500

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Yeah, I'm recharging my system this evening and was going to just wait for it to leak out again before messing with the cycle switch or anything else. So that's a handy piece of info
 

bugdewde

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Ok.... I put pressure gauges on it today.
About 80 degrees and 90% humidity.

Today, the compressor did NOT cycle off. It has in the past. Don't know what's going on there.

The high pressure (service manual states max of 330) is 148-150.
The low pressure (service manual states a max of 32) is 48-50.

The orifice/expansion tube was hot right before it (coming from condenser). It's union had condensation on it and was cold.

The lines at the accumulator were cool.... Not cold and no condensation.

I'm having trouble figuring out the evaporator lines inlet & outlet. Im assuming inlet is small higj pressure line (cold with condensation), but I can't determine which is the outlet.....????

The higher, low side reading has me puzzled. Maybe overcharged?

Check out my video for maybe some clarification on what I'm looking for and what I should be seeing/checking for.

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bugdewde

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1995 K2500 Suburban with rear air.

So I took some pics of the AC lines after a little condensation got on them to help identify any issues.

Compresser:
2 large lines are COLD with condensation.
1 small line (with high pressure service port) HOT.

Orifice Tube:
HOT on condenser side.
COLD with condensation on large nut/union and line going to accumulator.

Accumulator: (where i need help ID-ing lines)
Top small line (on inner fender) COLD
Second small line down (dirty) HOT
2 Large low pressure lines COLD
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I can't identify which 2 lines i need test for temperature on the accumulator inlet and outlet.
I'm assuming the inlet is one of the small high pressure lines..... And no idea on which one is the outlet. Any help?
 

east302

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I'm having trouble figuring out the evaporator lines inlet & outlet. Im assuming inlet is small higj pressure line (cold with condensation), but I can't determine which is the outlet.....????



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The line coming from the condenser goes to the evaporator. The evaporator outlet is up top, the accumulator nut is near the firewall.

Or, that’s how it is on my 98.

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It sounds like you have this already, but in case you don’t...

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