A/C compressor only comes on when I jump it

1995Beast

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1995 Mustang GT. Every year I put a can of freon in my car because it has a small leak and I do not know how to fix it nor do I want to pay a mechanic to do so. Well this year my compressor wouldn't even kick on. I jumped the switch on top of the canister with a paperclip and the compressor soon kicked on. I tried to hurry up and add some freon but something seemed off.
When I check the pressure at the line when the compressor is off, it reads at a dangerously high number. When I check the line when the compressor is not running, it is at zero.

Where should I go from here?

Many thanks,
-Jared
 
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Noobz347

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1995 Mustang GT. Every year I put a can of freon in my car because it has a small leak and I do not know how to fix it nor do I want to pay a mechanic to do so. Well this year my compressor wouldn't even kick on. I jumped the switch on top of the canister with a paperclip and the compressor soon kicked on. I tried to hurry up and add some freon but something seemed off.
When I check the pressure at the line when the compressor is off, it reads at a dangerously high number. When I check the line when the compressor is not running, it is at zero.

Where should I go from here?

Many thanks,
-Jared
Take your car to an automobile HVAC/ radiator shop. Get the leak repaired, the entire system sucked down and then properly serviced.

The cans of refrigerant that you get off the parts store shelves often has oil already in it. If you have been doing this for years then there's a pretty good chance that you have displaced most or all of the refrigerant with oil.

It happens pretty often. The oil is heavier than the refrigerant and doesn't boil off.
 

revhead347

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Which side is reading dangerously high, and what pressure is that? Too much oil, or too much air can definitely do that. It's probably about time to suck it all out, and fill it back up again. I generally don't consider fixing a leak over one can of refrigerant a year worth while. Especially if it's the evaporator that is leaking.

Kurt
 

1995Beast

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Which side is reading dangerously high, and what pressure is that? Too much oil, or too much air can definitely do that. It's probably about time to suck it all out, and fill it back up again. I generally don't consider fixing a leak over one can of refrigerant a year worth while. Especially if it's the evaporator that is leaking.

Kurt
I have only ever checked the rail on the driver side coming directly from the compressor "I didn't know there was another location to check". I just used a gauge that came off of one of those recharge kits you get from auto-zone. It reads "dangerously high" when the compressor is not working and 0 when I've got it jumped off. There is NO WAY it is full. I haven't used the car nor the a/c for a couple years now so my guess is it's completely empty.
So your advice would be to suck it all out, fix it, then fill it up again? Is this something I can do? Sounds very expensive if bringing it to a shop and I prefer to do stuff like this on my own to not only learn but save money in the process.
 

1995Beast

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Take your car to an automobile HVAC/ radiator shop. Get the leak repaired, the entire system sucked down and then properly serviced.

The cans of refrigerant that you get off the parts store shelves often has oil already in it. If you have been doing this for years then there's a pretty good chance that you have displaced most or all of the refrigerant with oil.

It happens pretty often. The oil is heavier than the refrigerant and doesn't boil off.
Is this something the average joe mechanic could pull off on his own? I've read about people slapping new o rings to their a/c units and recharging their own systems. I don't know what kind of job we are talking about price wise by taking it to the shop, but it doesn't sound cheap.
 

Noobz347

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Is this something the average joe mechanic could pull off on his own? I've read about people slapping new o rings to their a/c units and recharging their own systems. I don't know what kind of job we are talking about price wise by taking it to the shop, but it doesn't sound cheap.
It's one of those things that until you have a diagnosis, you're not going to know if it's an expensive job or a little job. If Joe mechanic has all of the 'doo-dads' necessary to vacuum pump an A/C system then he can do it. You could too. It just becomes a matter of your time and resources versus the cost of a shop.

You tell us... Do you want to try and walk-through troubleshooting yourself (this will require tools and time)?


Note: @jrichker might have some helpful steps when it comes to self-service A/C.
 

1995Beast

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It's one of those things that until you have a diagnosis, you're not going to know if it's an expensive job or a little job. If Joe mechanic has all of the 'doo-dads' necessary to vacuum pump an A/C system then he can do it. You could too. It just becomes a matter of your time and resources versus the cost of a shop.

You tell us... Do you want to try and walk-through troubleshooting yourself (this will require tools and time)?


Note: @jrichker might have some helpful steps when it comes to self-service A/C.
Yes sir I have plenty of time rn. I have a good bit of tools and would be willing to purchase more for the greater good and if they weren't crazy expensive.
 
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Noobz347

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You may want to begin by seeing if you can get your hands on a set of gauges:


Some of these other dudes should be able to recommend what to get etc.. I'm no A/C wizard. I've only dabbled into the occult. :O_o:

@74stang2togo might be able to assist in the A/C tool department as well.
 

1995Beast

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Dang well if anybody comes up with or finds a good structured thread then let me know! My head gets kinda fuzzy reading all the threads that go in 15 different directions.
 

Noobz347

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Dang well if anybody comes up with or finds a good structured thread then let me know! My head gets kinda fuzzy reading all the threads that go in 15 different directions.

Give a couple of those folks that I pinged above, some time to get a look at this thread. They'll be along. They're both regulars.
 

74stang2togo

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An A/C system will read high, on the low pressure side, (especially on one of those Autozone "gauges" that are notorious for being wildly innaccurate) when the compressor isn't running because the system is equalized.

The fact that it's reading zero when you jump the compressor means there's a blockage in a line or hose upstream of the inlet port on the compressor. Most of the "DIY Recharge" kits sold at the parts stores have a stop-leak compound in them, that compound, in small amounts is harmless. For a habitual refiller like yourself, you've probably gummed up the orifice tube or evaporator.

Take it to a professional at this point, it's beyond being economical for a shade-tree. Make sure you tell them what you've been doing and if possible, show them the can of the product you've been using so they can decide A: Whether or not to service it with their machine, as those products can damage them and B: So they know ahead of time what they're looking for.

(I work on cars for a living, including A/C systems.)
 

1995Beast

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An A/C system will read high, on the low pressure side, (especially on one of those Autozone "gauges" that are notorious for being wildly innaccurate) when the compressor isn't running because the system is equalized.

The fact that it's reading zero when you jump the compressor means there's a blockage in a line or hose upstream of the inlet port on the compressor. Most of the "DIY Recharge" kits sold at the parts stores have a stop-leak compound in them, that compound, in small amounts is harmless. For a habitual refiller like yourself, you've probably gummed up the orifice tube or evaporator.

Take it to a professional at this point, it's beyond being economical for a shade-tree. Make sure you tell them what you've been doing and if possible, show them the can of the product you've been using so they can decide A: Whether or not to service it with their machine, as those products can damage them and B: So they know ahead of time what they're looking for.

(I work on cars for a living, including A/C systems.)
Fair enough :(. Thank you for the input.
 

revhead347

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The basic tools you need are a good set of gauges, and a vacuum pump. In the age of Amazon, Harbor Freight, and ebay, those can be had cheap. There are two types of vacuum pumps, electric and air driven. The air driven ones are dirt cheap, but you need a lot of air flow to run them, so you need a big compressor. If you take it to a pro, they will diagnose it very quickly.

The reason your gauge is reading dangerously high is because you are putting it on the high side, and it's made to read the pressure on the low side.

Kurt
 

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74stang2togo

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The reason your gauge is reading dangerously high is because you are putting it on the high side, and it's made to read the pressure on the low side.

Kurt
That's not possible, the fittings are two different sizes.
 

revhead347

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That's not possible, the fittings are two different sizes.
I don't even remember a valve on the compressor. That's definitely not the normal place to fill or check AC. These cars are R134a with the pop on style connectors. I don't know if someone screwed a conversion cap on there or something. Who knows, but that is definitely not where you check the low pressure where a hose from a can would normally be used. Low pressure is checked on the line from the evaporator to the compressor.

Kurt
 
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74stang2togo

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I don't even remember a valve on the compressor. That's definitely not the normal place to fill or check AC. These cars are R134a with the pop on style connectors. I don't know if someone screwed a conversion cap on there or something. Who knows, but that is definitely not where you check the low pressure where a hose from a can would normally be used. Low pressure is checked on the line from the evaporator to the compressor.

Kurt
I didn't say there was a valve on the compressor, nor that it was the normal place to check or fill AC. I was talking about the port on the compressor that the suction line would bolt to (a.k.a "the line from the evaporator to the compressor").

Again, R134a service ports are two different sizes, you can't screw up which one is where.

I do A/C work on cars FOR A LIVING, you're not telling me anything I don't know, and you're putting misinformation in this thread and doing nothing to help.

ac-system-645.jpg


As I said before, the pressure is dropping to zero when he engages the compressor because there's a blockage somewhere on the low pressure side of the system. The low side port is on the suction line running to the compressor, the gauge is bottoming out when he engages the compressor because he's creating vacuum in the low side of the system. I'd bet a paycheck that if he had a full set of gauges that the high side is reading VERY high at the same time.

Again, the reason those bogus recharge kit "gauges" read "dangerously high" when the compressor is OFF, has nothing to do with which port it's hooked up to. If he magically made it fit the high side service port, it'd read exactly the same when the compressor isn't running because the system EQUALIZES when it's not operating. That equalized pressure is usually well above the operating range of the low side of the system.

I spend my summers fixing A/C systems that people with your level of "knowledge" have worked on.
 
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revhead347

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I didn't say there was a valve on the compressor, nor that it was the normal place to check or fill AC. I was talking about the port on the compressor that the suction line would bolt to (a.k.a "the line from the evaporator to the compressor").
The OP said there was a valve on the compressor. Your diagram does not have that valve on it. I'm just trying to figure out what's going on. You're just being mean. I'm going to report you to a mod. Oh wait never mind.

I am not spreading misinformation. I've probably done more AC jobs than you have. I did one 3 weeks ago, and it blows ice cold. I've fixed many after a "pro" worked on them. So let's stop the BS, and get to the bottom of what's going on here, without comparing penis length. Of the short list of people regularly on this forum, I'm a top 5 fastest car, 25 years of experience, and top 5 with total mechanical experience, so you need to put your opinion in perspective when you pass judgement on my knowledge. I certainly don't know everything, but I sure as hell answer a lot more questions than I ask. The OP said there is a valve on the compressor that he is filling and or checking from. He needs to know that's not how you do it.

Kurt
 
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74stang2togo

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The OP said there was a valve on the compressor.
No he didn't, he said it was on the line coming from the compressor, and you quoted ME on that post, hence my countering it. Confusion all around! Yay! :jester:

I'm just trying to figure out what's going on. You're just being mean. I'm going to report you to a mod. Oh wait never mind.
I'll do it for you. Hey @Noobz347 ! There you go. Now I'm gonna be in trouble with my boss, ya happy? :(

I am not spreading misinformation.
I was referring to this earlier post:
The reason your gauge is reading dangerously high is because you are putting it on the high side, and it's made to read the pressure on the low side.
But, I digress.

I've probably done more AC jobs than you have.
I seriously doubt that, I live in Texas and have worked on cars professionally for most of the last 17 years, and last 5 continuously. People in Texas will fix the A/C on a car with an engine knock, a slipping transmission, four bad tires, grinding brakes, and a leaking radiator, it's priority #1 for most people here.

I've fixed many after a "pro" worked on them. So let's stop the BS, and get to the bottom of what's going on here, without comparing penis length. Of the short list of people regularly on this forum, I'm a top 5 fastest car, 25 years of experience, and top 5 with total mechanical experience, so you need to put your opinion in perspective when you pass judgement on my knowledge. I certainly don't know everything, but I sure as hell answer a lot more questions than I ask. The OP said there is a valve on the compressor that he is filling and or checking from. He needs to know that's not how you do it.
Hello pot! :doh:


EDIT: I just re-read my earlier post. I did come across as bitchy... For what it's worth, I apologize for that. It's been a long, very bad day (I won't bore you with the details here), and I shouldn't have been so damned grouchy with you for it, it's not your fault.
 
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