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SuperNewbie
1995 Thunderbird LX 4.6 red
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No, our cars have an expansion valve.
 

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So then, what options do I have?

My A/C functions, but it's not very cold.
Typically when people top off with the can, it works great for a season and then next year same problem.

If you've lost charge you have a leak.

Only way to determine current charge is with a recovery machine or recovery tank / scale. You will find a low charge. Pressure test and check for leaks. Replace Schrader valves. Vacuum below 500 microns and then re charge to the level indicated on the radiator support tag.
 

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1994 Cougar XR7 DOHC/5-Speed
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So then, what options do I have?

My A/C functions, but it's not very cold.
The right way to do it is to have the system fully evacuated and the have the correct amount of weighed refrigerant put back in, eg take it to a shop.

The not-right way that's still better than those recharge systems is to buy a set of AC gauges and use the 12oz refrigerant only cans. Using those you can at least purge the lines so no air gets into the system but its still not going to be a truly accurate charge, you can get into the ballpark enough to blow cold air using the pressure/temperature charts though but you might end up overfilling the system.

Like Dan said you probably have a leak in the system somewhere, topping off the charge without finding it isn't a permanent fix
 

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its still not going to be a truly accurate charge


You can weigh a 12 oz. Can the same .. all you need is a scale. 😉

1997Thunderbird - I build large scale commercial refrigeration systems, by the way .. same difference.

All you need is: a vacuum pump, dual needle gauge manifold and hose set, scale, and micron gauge. Most people don't have or want to invest in this equipment .. it's not cheap.

Matt's method is the most conventional / economical way to get a good charge but you still need the proper tools - depending on your auto stores, some or all are available to rent.

Edit: if you want to find the leak, you may need a bottle of Nitrogen and regulator setup as well.
 

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1994 Cougar XR7 DOHC/5-Speed
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View attachment 49982

You can weigh a 12 oz. Can the same .. all you need is a scale. 😉
I mean if you "top it off", there's no way of knowing how much refrigerant is left in the system to know how much weight to put in from the 12oz can(s). Doing it the right the system needs to be fully evacuated, legally and ethically requiring a visit to a shop to pull it one way or another, from there you can do it yourself using all that stuff to refill after finding/repairing the leak source.
 

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I mean if you "top it off", there's no way of knowing how much refrigerant is left in the system to know how much weight to put in from the 12oz can(s). Doing it the right the system needs to be fully evacuated, legally and ethically requiring a visit to a shop to pull it one way or another, from there you can do it yourself using all that stuff to refill after finding/repairing the leak source.
Correct. See post #7. Topping off a leaking system won't make a difference in charge amount when its going to come back out anyways - it only verifies that the system is leaking and then the moral / legal obligation is to have it repaired. This only applies if you have the Section 608 ( Types 1-3 ) or Section 609 ( mobile ) certifications. 😉
 

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When I took automotive HVAC class at the local community college I was impressed to learn that systems are charged based on quantity of the refrigerant by weight, rather than system pressure as implied by all the DIY cans of refrigerant commercially available. I had my '95 properly serviced back in 2016 at a local auto a/c shop that I like. When the performance was weak in 2019 I added a can and its been nice and cold since. A/C service was always one of those things I left to the pros and still do for newer vehicles with less tolerance for discrepancy like my wife's Fusion or my new F150. But on the ol' T-bird I try DIY first and then hire a pro if needed. Other advice I gathered from HVAC class: never buy DIY cans with sealer, that messes up the system. Good luck with the a/c in the '97.
 

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SuperNewbie
1995 Thunderbird LX 4.6 red
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That's the point: the disclaimer reads that some vehicles with an expansion valve cannot be accurately filled by using the pressure reading.
Our cars use an orifice tube, not an expansion valve. But yes those cans are junk, you’re putting air into the system through the hose
I apologize I did mean to say orifice tube.
 

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Discussion Starter · #16 ·
When the performance was weak in 2019 I added a can and its been nice and cold since.
Ok, I gave this a try. Bought a 12 oz. can without sealer and bought a hose with pressure gauge.

I added refrigerant for a good 30 seconds with interruptions. Problem was: the pressure never changed; it always stayed at 30 psi.
So I stopped because there was no way to tell what I was or was not accomplishing. I haven't actually driven yet, so I'll see performance changes later, if any.
 

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1994 Cougar XR7 DOHC/5-Speed
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This kind of hose/gauge?




That's not really any different than using the recharge cans, the same problem I mentioned earlier exists regarding air being introduced into the system. With manifold gauges that read both high and low side you can at least purge out the air from in the line the low side through the fill line, and then purge the fill line from the schrader valve after the refrigerant can is hooked up and opened.
 
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