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A/C questions (novice)

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Old 07-05-2018, 03:14 PM
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Hey guys,

So my 95 XJ's A/C does not work at all. By that I mean it doesn't blow a bit of cold air (more than just the Vent setting). As I live in New England I haven't worried too much about this since we only get 2 months of really hot weather, however since the last week has been painfully hot and humid, I'm contemplating at least -trying- to diagnose and fix the A/C system. Of all the auto components, however, the A/C system is one that I know virtually nothing about beyond the very general basic idea of how it works. I'm hoping I can get some of the more knowledgeable folks around here to help me work my way through figuring this out.

What I'm thinking is that there is a leak somewhere that over time has caused the refrigerant to completely drain out of my system. So my thought is to do the following:
1 - Check that the compressor/clutch actually kicks on when the A/C/Def is on and kicks off when the A/C/Def is off. Also, obviously, that the aux fan also comes on when the A/C is on. I'm pretty sure it does, but just to be sure I'll check it at the same time.
2 - Assuming that the compressor is at least running when it's supposed to, I'll hook up one of the DIY A/C recharge kits and charge the system according to the instructions.
3 - Immediately after step 2, I'll do one of the U/V test kits and see if there's an obvious spot that is leaking. I've never used one of these before, but I've seen them being sold a the local parts retailers recently.

So my questions are:
1 - Are these the proper diagnostic steps to follow and am I missing anything?
2 - Are there any pitfalls in inspecting the system that I should be aware of or components to focus on?
3 - Do I have to worry about oil vs. refrigerant or anything like that? I've read things in the past indicating that there's supposed to be a proper level of oil and that it's critical to not damaging things and hence it's got me paranoid about doing A/C related work myself.

My thought is that if I can get the A/C system working without spending more than a couple hundred bucks, that would be awesome. If it looks like it would take closer to $500+, then I'll probably consider it not worth the cost and effort and save my money towards a new Jeep in a few years.

Thanks guys!
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Old 07-05-2018, 03:37 PM
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Originally Posted by PatHenry View Post
Hey guys,

So my 95 XJ's A/C does not work at all. By that I mean it doesn't blow a bit of cold air (more than just the Vent setting). As I live in New England I haven't worried too much about this since we only get 2 months of really hot weather, however since the last week has been painfully hot and humid, I'm contemplating at least -trying- to diagnose and fix the A/C system. Of all the auto components, however, the A/C system is one that I know virtually nothing about beyond the very general basic idea of how it works. I'm hoping I can get some of the more knowledgeable folks around here to help me work my way through figuring this out.

What I'm thinking is that there is a leak somewhere that over time has caused the refrigerant to completely drain out of my system. So my thought is to do the following:
1 - Check that the compressor/clutch actually kicks on when the A/C/Def is on and kicks off when the A/C/Def is off. Also, obviously, that the aux fan also comes on when the A/C is on. I'm pretty sure it does, but just to be sure I'll check it at the same time.
2 - Assuming that the compressor is at least running when it's supposed to, I'll hook up one of the DIY A/C recharge kits and charge the system according to the instructions.
3 - Immediately after step 2, I'll do one of the U/V test kits and see if there's an obvious spot that is leaking. I've never used one of these before, but I've seen them being sold a the local parts retailers recently.

So my questions are:
1 - Are these the proper diagnostic steps to follow and am I missing anything?
2 - Are there any pitfalls in inspecting the system that I should be aware of or components to focus on?
3 - Do I have to worry about oil vs. refrigerant or anything like that? I've read things in the past indicating that there's supposed to be a proper level of oil and that it's critical to not damaging things and hence it's got me paranoid about doing A/C related work myself.

My thought is that if I can get the A/C system working without spending more than a couple hundred bucks, that would be awesome. If it looks like it would take closer to $500+, then I'll probably consider it not worth the cost and effort and save my money towards a new Jeep in a few years.

Thanks guys!
1. Jump the low pressure switch with a paper clip to see if it kicks in and pumps. Do not run it but a couple seconds if it does.

2. If it is completely flat, which I am sure it probably is considering the time that has gone by, It needs to go to the shop and be vacuumed down and then refilled properly. A DIY kit is not going to get enough in it to make it work properly.

Unfortunately once they are flat then they need to be vacuumed down before refilling. You can do this yourself if you want to try, it's not hard but it takes a vacuum pump and a set of gauges. You may be able to rent a vacuum pump and gauges are not too bad of an investment if you will be working on this, or other A/C systems yourself again in the future.
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Old 07-05-2018, 03:52 PM
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Originally Posted by Bugout4x4 View Post
1. Jump the low pressure switch with a paper clip to see if it kicks in and pumps. Do not run it but a couple seconds if it does.

2. If it is completely flat, which I am sure it probably is considering the time that has gone by, It needs to go to the shop and be vacuumed down and then refilled properly. A DIY kit is not going to get enough in it to make it work properly.

Unfortunately once they are flat then they need to be vacuumed down before refilling. You can do this yourself if you want to try, it's not hard but it takes a vacuum pump and a set of gauges. You may be able to rent a vacuum pump and gauges are not too bad of an investment if you will be working on this, or other A/C systems yourself again in the future.
Edit - I'm going to assume straightaway that it's flat since it's never worked in the 9 months I've had the Jeep.

Hmmm.. would I be able to do the vacuum -and refill- myself if I invested in a set of gauges and got my hands on a vacuum pump?

I'm not averse to buying some equipment if I can make use of it more than once or twice.

Once I had it vacuumed and refilled (whether by myself or at a shop) at that point would I go ahead and do the UV dye test? (I suppose I should say, if I got it to the point of vacuum and refill myself, since if I had a shop do it I have to think the sensible thing would be to have the shop do the diagnosis of what's broken.)

Last edited by PatHenry; 07-05-2018 at 03:54 PM.
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Old 07-05-2018, 04:13 PM
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Originally Posted by PatHenry View Post
Edit - I'm going to assume straightaway that it's flat since it's never worked in the 9 months I've had the Jeep.

Hmmm.. would I be able to do the vacuum -and refill- myself if I invested in a set of gauges and got my hands on a vacuum pump?

I'm not averse to buying some equipment if I can make use of it more than once or twice.

Once I had it vacuumed and refilled (whether by myself or at a shop) at that point would I go ahead and do the UV dye test? (I suppose I should say, if I got it to the point of vacuum and refill myself, since if I had a shop do it I have to think the sensible thing would be to have the shop do the diagnosis of what's broken.)
We will walk you through it if you want to do it yourself and issues can be resolved as they come up. Even at the shop the sequence would be... Oil... Dye... then Refrigerant. If it doesn't leak the dye wont hurt anything to go along and ride for the duration. If it's a big leak you will see it right away, but It may be such a slow leak that it might only need one can a year to top it off for the summer. About all mine are this way.

But you have to fill it up to pressure and run it to find out anyhow.
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Old 07-05-2018, 04:24 PM
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Here's where to start...

1. decide if you are going to do it yourself or not and commit to it if so. lol

2. Jump the low pressure switch to see if the compressor runs.

3. take a piece of wire or a probe and poke the "valve core" in the charge fitting to see if you currently have any pressure or not.

4. Now if it were mine... Before doing anything else at this point I would unhook every line and fitting I can and replace all the O-rings as a preventative measure before filling. Doing it now is better than having to start all over again just to replace an O-ring. One of the O-rings is most likely the present leak anyhow so changing these just might fix the issue for good.

Then you can go on to the system vacuum and charge.

Last edited by Bugout4x4; 07-05-2018 at 04:29 PM.
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Old 07-05-2018, 04:44 PM
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Originally Posted by Bugout4x4 View Post
Here's where to start...

1. decide if you are going to do it yourself or not and commit to it if so. lol

2. Jump the low pressure switch to see if the compressor runs.

3. take a piece of wire or a probe and poke the "valve core" in the charge fitting to see if you currently have any pressure or not.

4. Now if it were mine... Before doing anything else at this point I would unhook every line and fitting I can and replace all the O-rings as a preventative measure before filling. Doing it now is better than having to start all over again just to replace an O-ring. One of the O-rings is most likely the present leak anyhow so changing these just might fix the issue for good.

Then you can go on to the system vacuum and charge.
Sounds good - I'll start on this plan and report back as I go.
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Old 07-05-2018, 04:49 PM
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If the compressor works, then you have a leak. Might as well just replace all the O rings at the fittings, front seal on the compressor, suck it down and recharge.
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Old 07-05-2018, 05:02 PM
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PatHenry,


I went through the same thought process on another vehicle. Ultimately, having your AC serviced by someone you don't trust is so shady, that I decided to invest in myself like I do with most other automotive jobs. I got a vaccuum pump / gauge set kit from Amazon, and also bought an R134a sniffer (better than a die kit). I can't remember what the total cost was, I didn't got with the cheapest options but with names that had been recommended, had good reviews, etc. There are pretty big variances in the price of gauge kits, but it is one of those things where if you don't get a certain quality, you might as well throw them away. They need to work properly and accurately.


The work itself was as easy as anything else we do with our vehicles. Not a whole lot to it when you have the right tools. I vacuumed the system down, waited some time to verify it wasn't leaking (holds the vacuum), and then recharged to the appropriate pressures/levels. I watched a lot of youtube and read pages before diving it. But it was pretty straight forward.
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Old 07-05-2018, 05:09 PM
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Get your hands on a vacuum pump pump and a set of gauges if you can. You will need the fittings if it is r134a. Its most likely flat. Vac it down to 30"hg then add freon. You can get the kit at any auto parts store.
Its a quick way to get some cool air then check for leaks.
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Old 07-05-2018, 05:28 PM
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Originally Posted by jordan96xj View Post
PatHenry,


I went through the same thought process on another vehicle. Ultimately, having your AC serviced by someone you don't trust is so shady, that I decided to invest in myself like I do with most other automotive jobs. I got a vaccuum pump / gauge set kit from Amazon, and also bought an R134a sniffer (better than a die kit). I can't remember what the total cost was, I didn't got with the cheapest options but with names that had been recommended, had good reviews, etc. There are pretty big variances in the price of gauge kits, but it is one of those things where if you don't get a certain quality, you might as well throw them away. They need to work properly and accurately.


The work itself was as easy as anything else we do with our vehicles. Not a whole lot to it when you have the right tools. I vacuumed the system down, waited some time to verify it wasn't leaking (holds the vacuum), and then recharged to the appropriate pressures/levels. I watched a lot of youtube and read pages before diving it. But it was pretty straight forward.
Absolutely. One difference in what I would do though. I'm cheap and wouldn't buy the sniffer yet, It might take two years to drop enough for the low pressure switch to cycle. So I would wait to see if it even goes down fast or not. May never actually need to buy it.
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Old 07-05-2018, 05:50 PM
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All of the above is solid advice, I'll add that replacing the dryer should be done if the system is empty before you charge the system. Also make sure you add oil after you vacuum the system or the compressor will burn up in a short amount of time. Replacing the o-rings imho is overkill unless you know they're leaking, they usually leak if the A/C isn't used for a long period of time but once you put a charge in they usually tighten back up. Make sure your' fan clutch and e-fan are in good working order too.
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Old 07-05-2018, 06:04 PM
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Originally Posted by kbeam418 View Post
Replacing the o-rings imho is overkill unless you know they're leaking, they usually leak if the A/C isn't used for a long period of time but once you put a charge in they usually tighten back up.
Wrong... You obviously have not had to evacuate countless systems back down just because of an O-ring. He will not have an evacuation unit to reclaim and reuse the refrigerant that comes out if he has to do it over again just because of a .50 cent O-ring. He will be forced to waste all that freon. "Unless you know they are leaking" No better way of knowing they WILL NOT leak is to change them while it is empty before ever starting the recharge process. If they are not leaking now, they will in the near future it's a 1995 model. Could be stepping over a dollar to pick up a dime...

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Old 07-05-2018, 06:18 PM
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Originally Posted by Bugout4x4 View Post
Wrong... You obviously have not had to evacuate countless systems back down just because of an O-ring. He will not have an evacuation unit to reclaim and reuse the refrigerant that comes out if he has to do it over again just because of an O-ring. He will be forced to waste all that freon. "Unless you know they are leaking" No better way of knowing they WILL NOT leak is to change them while it is empty before ever starting the recharge process. If they are not leaking now, they will in the near future it's a 1995 model.
Like I said "in my opinion;" I wouldn't change them on my Jeep (which I still need to fix the A/C on) but that's just me. If it pulls down to 30 hg and maintains it for one hour (24 hours is best) it's not leaking bad. That's what I've been told by HVAC techs anyways. The reason why I wouldn't mess around with o-rings is simply because the parts haven't been touched for 23 years so you could potentially crack a line, break the evaporator etc. I'd rather top my A/C off once a year then spend an hour in a junkyard plus spend more money just because an o-ring might be bad. I've driven a lot of rust buckets and I've not once had an o-ring leak so bad that it couldn't make it through the summer.

Last edited by kbeam418; 07-05-2018 at 06:19 PM. Reason: Spelling
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Old 07-05-2018, 06:35 PM
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Originally Posted by kbeam418 View Post
Like I said "in my opinion;" I wouldn't change them on my Jeep (which I still need to fix the A/C on) but that's just me. If it pulls down to 30 hg and maintains it for one hour (24 hours is best) it's not leaking bad. That's what I've been told by HVAC techs anyways. The reason why I wouldn't mess around with o-rings is simply because the parts haven't been touched for 23 years so you could potentially crack a line, break the evaporator etc. I'd rather top my A/C off once a year then spend an hour in a junkyard plus spend more money just because an o-ring might be bad. I've driven a lot of rust buckets and I've not once had an o-ring leak so bad that it couldn't make it through the summer.
You are absolutely right about being careful when taking them apart to replace O-rings. But these are easy, the 95 has quick couplers right? Here's the deal, as an HVAC tech I don't like doing things twice and wasting refrigerant. O-rings are cheap, change them and be done with it. The customer will appreciate that you took the extra care and effort.

Like I said, you haven't seen it happen as many times as I have, And yes they do dry out, shrink and split.
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Old 07-05-2018, 06:40 PM
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Originally Posted by PatHenry View Post
2 - Are there any pitfalls in inspecting the system that I should be aware of or components to focus on?
3 - Do I have to worry about oil vs. refrigerant or anything like that? I've read things in the past indicating that there's supposed to be a proper level of oil and that it's critical to not damaging things and hence it's got me paranoid about doing A/C related work myself.
Why nobody never emphasizes safety in these threads is entirely beyond me. When you are working around a properly operating A/C system it is under a substantial amount of pressure. Chart follows:






It is imperative that you wear eye protection in case something lets loose and you are exposed to refrigerant, it can happen in an instant and you won't be able to get another pair of eyes.
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