A/C won't cool - Toyota Tacoma Forum
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post #1 of 10 (permalink) Old 08-19-2019, 03:51 PM Thread Starter
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A/C won't cool

So my A/C stopped working after a year of not using the truck as a daily (I only drove it randomly). I got married, bought a house, etc. so needless to say, dailying the truck became financially appealing... but I've driven 7 months without A/C. Initially, I had a slight leak in one of the valves on the lines, so I had the system evacuated and I replaced the valve. I had the system refilled by my friend who is a residential A/C tech and we noticed the compressor try to come on and then shut off. He suggested it might be the pressure switch in the evaporator. I tried jumping that, no dice, compressor wouldn't start. So, I ran a wire from the compressor to the battery and got it to start, but the A/C will not blow cold. I know my lines are charged and they held vacuum for over an hour before being charged, thus I know there are no leaks. Could I have a stuck expansion valve? What else should I consider? This is on a 96 Tacoma Xcab, rwd.

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post #2 of 10 (permalink) Old 08-19-2019, 04:45 PM
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Re: A/C won't cool

Really hard to say without installing gauges on it to monitor low and high side pressures
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post #3 of 10 (permalink) Old 08-19-2019, 06:05 PM
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Re: A/C won't cool

A/C isn't something i know much about, but ...

It seems to me the pressure switch theory might be correct. If the A/C was turned off while you were charging the system I can't figure out how the compressor would try to activate unless the pressure switch was somehow triggering it.

Here (attached) is the 1996 A/C circuit diagram.
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File Type: pdf AC-AirCondCircuit.pdf (42.8 KB, 2 views)

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post #4 of 10 (permalink) Old 08-19-2019, 06:09 PM
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Re: A/C won't cool

Here (attached) is the 1995.5 / 1996 A/C pressure switch test procedure.
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File Type: pdf pressure.pdf (27.3 KB, 3 views)

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post #5 of 10 (permalink) Old 08-20-2019, 07:59 AM Thread Starter
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Re: A/C won't cool

Quote:
Originally Posted by ZIP671 View Post
Really hard to say without installing gauges on it to monitor low and high side pressures
I've actually got gauges. I need to test them out again and see where the pressures are sitting.

Quote:
Originally Posted by Enola Gaia View Post
A/C isn't something i know much about, but ...

It seems to me the pressure switch theory might be correct. If the A/C was turned off while you were charging the system I can't figure out how the compressor would try to activate unless the pressure switch was somehow triggering it.

Here (attached) is the 1996 A/C circuit diagram.
I had the system set to on when I was charging it actually. The compressor initially grabbed and was spinning, then the clutch let go. I always wonder where you get all this awesome info about Tacomas lol, I'll look at the PDFs you uploaded. Thanks Enola!

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post #6 of 10 (permalink) Old 08-20-2019, 04:18 PM
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Re: A/C won't cool

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Originally Posted by MatosTaco View Post
I've actually got gauges. I need to test them out again and see where the pressures are sitting.
I had the system set to on when I was charging it actually. The compressor initially grabbed and was spinning, then the clutch let go.

I attached the EWD which has a System Outline of A/C operation.
It Contains good info


I'm curious as to why you don't have power going to your compressor to engage the magnetic clutch.
Either a fuse, an open circuit between the amplifier and compressor... or the amplifier isn't seeing what it needs to see in order to send out the needed voltage.
But... being that you directed voltage from the battery to the clutch and forced the compressor to engage/spin... and yet still didn't cool is quite odd.
so either the compressor isn't pumping, the system has insufficient refrigerant, too much refrigerant, or a restriction.
Still comes back to being easier to diagnose with a gauge set
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File Type: pdf 96AC.pdf (74.2 KB, 3 views)
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post #7 of 10 (permalink) Old 08-20-2019, 04:27 PM
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Re: A/C won't cool

A/C Diagnosis attached
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File Type: pdf Gauge Diag.pdf (129.3 KB, 6 views)
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post #8 of 10 (permalink) Old 08-20-2019, 04:41 PM Thread Starter
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Re: A/C won't cool

Quote:
Originally Posted by ZIP671 View Post
I attached the EWD which has a System Outline of A/C operation.
It Contains good info


I'm curious as to why you don't have power going to your compressor to engage the magnetic clutch.
Either a fuse, an open circuit between the amplifier and compressor... or the amplifier isn't seeing what it needs to see in order to send out the needed voltage.
But... being that you directed voltage from the battery to the clutch and forced the compressor to engage/spin... and yet still didn't cool is quite odd.
so either the compressor isn't pumping, the system has insufficient refrigerant, too much refrigerant, or a restriction.
Still comes back to being easier to diagnose with a gauge set
Thanks for the data. I'll read those over and see if I can figure something out!

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post #9 of 10 (permalink) Old 08-21-2019, 05:01 PM
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Re: A/C won't cool

Quote:
Originally Posted by MatosTaco View Post
So my A/C stopped working after a year of not using the truck as a daily (I only drove it randomly). I got married, bought a house, etc. so needless to say, dailying the truck became financially appealing... but I've driven 7 months without A/C. Initially, I had a slight leak in one of the valves on the lines, so I had the system evacuated and I replaced the valve. I had the system refilled by my friend who is a residential A/C tech and we noticed the compressor try to come on and then shut off. He suggested it might be the pressure switch in the evaporator. I tried jumping that, no dice, compressor wouldn't start. So, I ran a wire from the compressor to the battery and got it to start, but the A/C will not blow cold. I know my lines are charged and they held vacuum for over an hour before being charged, thus I know there are no leaks. Could I have a stuck expansion valve? What else should I consider? This is on a 96 Tacoma Xcab, rwd.
I have my EPA 608 & 609. Based on what you've tried, I'm guessing another leak. If the compressor is turning (with power directly to it like you did) and the fan is blowing, it should blow cold air if it's still charged. R-134a is a relatively small molecule compared to R-12 so once an oring dries out leaks can be a real problem. Check the pressures with gauges and see what they read. FWIW, my 96 2WD read 245 hi/45 low after a fresh charge of 23 oz. If it is low, vacuum the system down using a vacuum pump and isolate the low side gauge to see if it holds vacuum. If it holds (30 mins or more), charge it with some R-134a with dye. If it returns to 0 you have a leak. With the dye, you'll be able to look at it with a black light and see the leak. Dye won't hurt your system but I'd advise against any leak sealer because those can plug an expansion valve. Dish soap & water in a spray bottle is also good for testing suspect areas but you can't get to everything like the evap or expansion valve. Usually, it's a compression fitting oring or compressor seal (like mine was) on my Nissan that sat for a couple years in a garage. The seal dried out and it was done.
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post #10 of 10 (permalink) Old 08-24-2019, 02:27 PM Thread Starter
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Re: A/C won't cool

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Originally Posted by rickalders View Post
I have my EPA 608 & 609. Based on what you've tried, I'm guessing another leak. If the compressor is turning (with power directly to it like you did) and the fan is blowing, it should blow cold air if it's still charged. R-134a is a relatively small molecule compared to R-12 so once an oring dries out leaks can be a real problem. Check the pressures with gauges and see what they read. FWIW, my 96 2WD read 245 hi/45 low after a fresh charge of 23 oz. If it is low, vacuum the system down using a vacuum pump and isolate the low side gauge to see if it holds vacuum. If it holds (30 mins or more), charge it with some R-134a with dye. If it returns to 0 you have a leak. With the dye, you'll be able to look at it with a black light and see the leak. Dye won't hurt your system but I'd advise against any leak sealer because those can plug an expansion valve. Dish soap & water in a spray bottle is also good for testing suspect areas but you can't get to everything like the evap or expansion valve. Usually, it's a compression fitting oring or compressor seal (like mine was) on my Nissan that sat for a couple years in a garage. The seal dried out and it was done.
Also very good advice. I'll try and check once this rain calms down and post an update. Thanks!

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