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Old 08-23-2021, 04:58 AM   #1
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Default AC not cold enough / low rpm

Hi everyone.

My truck’s AC blows cold air just fine after a recharge, but after some months it will stop blowing cold air like it was after I just recharged it. It still blows cold air enough to use it when it isnt hot outside, but on hot days it is just useless. Any ideas what it could be?

1 year passed since the recharge, and if the truck was leaking, wouldnt it stop blowing cold air at all?

In addition, when I turn on the AC the rpms drop from around 900 to 800 rpm. If I turn on the lights the rpms also drop a tiny bit.
My truck still has the original 50A alternator and a 56A battery (have to double check the battery amperage but I think that it is indeed 56A). Maybe the alternator and battery are too small? The only aftermarket parts that I installed was a regular stereo.

I know that you guys didnt get the TD23 diesel engine in the US but, any ideas on what it could be?
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Last edited by PFDSA; 08-24-2021 at 12:14 AM. Reason: fixed rpm values
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Old 08-23-2021, 06:42 AM   #2
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So, is it the stock AC system? Not an addon... stock tubes, compressor and all? Original to '88? I'd suspect a lot of dry rot on the internal rubber bits. Ready to rebuild the system?

My take, at least...
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What he is saying is the aerodynamics of a D21 is a brick in the wind.
Probably at least as bad as a Jeep so worse than a cow.
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Old 08-23-2021, 07:19 AM   #3
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Quote:
Originally Posted by 89'HBV6 View Post
So, is it the stock AC system? Not an addon... stock tubes, compressor and all? Original to '88? I'd suspect a lot of dry rot on the internal rubber bits. Ready to rebuild the system?

My take, at least...
Yes, stock AC system, and as far as I know not a single part was replaced.
Thank you for the answer, but let’s hope that you’re wrong

Anyone else?
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Old 08-23-2021, 09:19 AM   #4
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The cost of resealing the AC system is cheap here in the states. Change the orings, expansion valve and the drier. Maybe replace the condenser too.
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Old 08-23-2021, 11:09 AM   #5
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Here in the U.S. that old a system would be an R-12, if not already converted. Big $$$ for the refrigerant, and not good to leak or vent. Which refrigerant is it currently using? If changing, then a new compressor, etc. would likely be needed.
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Old 08-23-2021, 01:21 PM   #6
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Both of my VG powered trucks are running r134 with all r12 parts. The lone exception is the pressure cutoff switch on the drier. That is a 134 sensor. R134 and r12 systems operate at different pressures which means less r134 is needed vs r12. I think the ballpark estimate is 80 to 85 percent.
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Old 08-23-2021, 02:47 PM   #7
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Have an AC shop diagnose the leak, and get the leak repaired; likely an O-ring, a shaft seal....


NEVER ADD ANY SEALANT OR REFRIGERANT CONTAINING SEALANT. UV dye is fine.
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Old 08-23-2021, 05:39 PM   #8
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My truck's AC just isn't real good. It doesn't leak or anything (at the moment) after I rebuilt it back in '13 or so. It does ok while the truck is moving and the engine is around 3k rpm or so. Slow speeds it's just an old AC system that is meant for R12 instead of R134. If you can get hold of R12 it works better but it's expensive.


If your revs are dropping that low you may need to check the idle up solenoid on the throttle body. I had to replace mine a few years ago.
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Old 08-23-2021, 06:37 PM   #9
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Quote:
Originally Posted by OldGreyBeast View Post
If your revs are dropping that low you may need to check the idle up solenoid on the throttle body. I had to replace mine a few years ago.
OGB... where did you get your solenoid from? I know it was 7-8+ years ago... I (sorta) discovered this part is NLA. The wax-solenoid, right?


BTW, my AC is similar to yours. Works, when I want it to... defrost the windscreen... but generally I don't need it, so it rarely gets used. It does still put out cool air, not really cold anymore.
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Quote:
Originally Posted by Deerhurst
What he is saying is the aerodynamics of a D21 is a brick in the wind.
Probably at least as bad as a Jeep so worse than a cow.
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Old 08-23-2021, 06:52 PM   #10
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My pathfinder has 40 degree air at the vent. R134. My condenser is leaking. I have a new one. It might even blow colder after it gets the new condenser. The old one is beat to hell.
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