Help wanted with broken ac

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matthew robertson

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I have a 74 dart sport with a 360. Ac does not work and I don’t know why, mixed with the vinyl seat it can be one hell of a sauna in there during the summer. With ac turned to max the clutch seems to grab then stop every 5 seconds or so, turns about half a rotation then stops again. Anyone have answers?

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Have you put any freon in it? And if so what kind. Do you have a set of gauges.
 
Anything is posable at this point.

Take it to an AC shop for diagnostic
 
matthew robertson said:
I bought one of those recharge kits and when I put the gauge on it read full so I kinda ruled that out, could it be just old age?
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No. If you are not doing a lot of this buy a cheap set of gauges lo and hi side. This will help with diagnostics of the system. Always were safety glasses when working on ac systems. Hi pressure and freon are a bad mix. Let us know when you get them and me or someone on here can help.
 
Really hard to guess at these things....Really gotta put guages on it...real ones, to know what's happening. Sadly, too often, a can will get put into a system that does'nt need more. A compressor is a pump, and it can only pump vapor,,,it can not pump a liquid.... this action is also harder on it that too little refrigerant as well. There should be a low pressure switch, which will isolate the compressor from the system to protect it from running with low pressure. Maybe you can check it with a multimeter and see if that's happening. If it's kicking out due to high pressure, that's tearing the compressor up everytime it tries to spin. HTH, Lefty71
 
All these cars have a low pressure cutout switch. When the compressor gets power it is in series with that switch. Evidently you have "just enough" refrigerant in the system to bring on the compressor, and when it starts to pump, it pulls down pressure in the low side of the system, below the switch cutoff.

You need to get yourself a service manual. And you probably need to pull the charge out and start over. WHY? Because you don't know what's in there. R12 has been outlawed now for many years. Someone else could have put most anything in there at this point.

Also look around "for stickers" or special fittings to try and determine if it's been converted to R134 or whether it likely still has R12 in the system

As old as this is, unless it's had hoses/ seals/ gaskets etc in the last 20 years, it most likely is leaky and won't hold a charge for long without further service work

You can download a 73 manual at MyMopar, but there is no 74. The 73 book is "close" on most of what you need EXCEPT WIRING. Wiring in 74 is very very different.
 
matthew robertson said:
I bought one of those recharge kits and when I put the gauge on it read full so I kinda ruled that out, could it be just old age?
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What do you call "reading full"? I mean no offense at all when I say this, but that sounds like an unformed phrase when discussing A/C. Can you get more specific?
 
RustyRatRod said:
What do you call "reading full"? I mean no offense at all when I say this, but that sounds like an unformed phrase when discussing A/C. Can you get more specific?
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Sorry for lack of context/info and knowledge haha, I’m 18 and this is my first “project” car. I assumed the ac would work the same as my daily driver but after reading other comments I now realize that it’s probably a different concept. I had bought a recharge kit and put a gauge that it came with on my ac and it read that the refrigerant was full
 
Best to vacuum the system down for an hour with a vacuum pump, that boils any moisture out of the system and removes it.

Then refill the system with the proper type of freon for your system. Lots of them have been converted to 134 freon. Can tell by the additional fittings at the fill ports.

Look in a manual and see how many oz. of freon it is supposed to take. Fill on the low pressure side only, with the car running, full on AC controls, and doors snd Windows closed. Fan on high.

Put a thermometer in the AC vent and see if you can get it to cool down to 50° degrees.

Remember these are older systems are less efficient than the new cars, so be a little patient.
 
You cannot tell "jack" from one of those single parts store gauges. You cannot see both sides functioning. You cannot "see" a restriction if there is one. Here is what I consider a bare minimum for A/C work as for gauges.
GAUGES.jpg

Do you maybe know any friends or acquaintances who might have a set and will come help you diagnose it? I would do it myself, but we're not local.
 
RustyRatRod said:
You cannot tell "jack" from one of those single parts store gauges. You cannot see both sides functioning. You cannot "see" a restriction if there is one. Here is what I consider a bare minimum for A/C work as for gauges.
View attachment 1715851085
Do you maybe know any friends or acquaintances who might have a set and will come help you diagnose it? I would do it myself, but we're not local.
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Set looks nice.
 
He's only 18, so let's help him out gentlemen. It sounds like it's short cycling. As 67 said, it could be the low pressure switch, too much head pressure, or a blocked accumulator/filter. You need to know what type of refridgerant you have in the system. Money spent for a professional diagnosis might well be worth it.
 
RustyRatRod said:
You cannot tell "jack" from one of those single parts store gauges. You cannot see both sides functioning. You cannot "see" a restriction if there is one. Here is what I consider a bare minimum for A/C work as for gauges.
View attachment 1715851085
Do you maybe know any friends or acquaintances who might have a set and will come help you diagnose it? I would do it myself, but we're not local.
Click to expand...
Man, Y'all are all Cool People!
 
Heck he's in Canada they probably wouldn't let me across the border. And it's cold up there and I ain't got no winter clothes for up there.
 
70dart340 said:
He's only 18, so let's help him out gentlemen. It sounds like it's short cycling. As 67 said, it could be the low pressure switch, too much head pressure, or a blocked accumulator/filter. You need to know what type of refridgerant you have in the system. Money spent for a professional diagnosis might well be worth it.
Click to expand...
I think when ur comes out of storage that’s what I’ll do. Seems like it might be a bit out of my grasp of experience and I’d rather it get done right since it’s not really much of a project but more of a driving show ready car. Thanks for being nice!:)

043A6944-58D0-4ECD-AE5B-2F82585461EF.jpeg
 
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