AC questions (1 Viewer)

[runthejoules]

I've replaced all the components to my 85 60's AC system including hoses and seals. Put a vaccum for 30+ min on the system to pull air and moisture. Refilled about 1/2 capacity with refrigerant, started truck, held the revs to 1300 or so and the compressor engaged and the pressure gauges began to adjust (low pressure began to drop and high began to raise). I continued to add 134a to the system and at some point the compressor turned off and now I can't get it to come back on. I'm seeing 55psi or so on the low side and about the same on the high side. Fuse is still good. Not sure what I could have done to keep the compressor from kicking on, and not sure how else to trouble shoot aside from releasing pressure and adding coolant until something happens. Anyone have similar experience? Any thoughts to trouble shoot?

thx

 

[BlackCat]

You could’ve overcharged it. Equal pressures mean the compressor isn’t working. Is it 134 now and was R12 previously?

 

[runthejoules]

yes it was r12 before, but I replaced everything that touches the coolant... compressor, condenser, drier, expansion valve, hoses and seals, so there shouldn’t be any residual r12 anywhere in the system. How do I know when I’ve charged too much? What low side pressure should I look for?

 

[BlackCat]

yes it was r12 before, but I replaced everything that touches the coolant... compressor, condenser, drier, expansion valve, hoses and seals, so there shouldn’t be any residual r12 anywhere in the system. How do I know when I’ve charged too much? What low side pressure should I look for?

That’s going to depend on your ambient air temps. Somewhere around 30-35 on the low side and around 200 or so on the high side- all depending on outside air temp. You can’t put the same amount of R134 in as you did R12- you put in less. I have approx 1.2lbs in my 60- it’s supposed hold I believe 1.7lbs of R12.

 

[runthejoules]

welp, now I've got the pressure dropped to 22 on the low side... still nothing. Compressor just doesn't engage.

 

[1972FJ55]

Amplifier issue?

The A/C Amp Thread

This thread is all about FJ60/FJ62 A/C amplifiers. You know, that little black box that mounts on the evaporator case behind the glove box. There are plenty of other threads concerning A/C amps and I thought about adding to those, but in the end decided that the information here breaks enough...

forum.ih8mud.com

 

[runthejoules]

Amplifier issue?

The A/C Amp Thread

This thread is all about FJ60/FJ62 A/C amplifiers. You know, that little black box that mounts on the evaporator case behind the glove box. There are plenty of other threads concerning A/C amps and I thought about adding to those, but in the end decided that the information here breaks enough...

forum.ih8mud.com

how would I test that? I worked at first...

 

[SteveH]

You could apply 12v directly to the compressor clutch, after disconnecting any factory wiring. This would at least allow you to see if the compressor engages as it should and generates pressure.

If you are using 12 oz. cans, how many did you put in the system? This should give you a rough idea if you have greatly overcharged it (which I doubt you have).

 

[runthejoules]

You could apply 12v directly to the compressor clutch, after disconnecting any factory wiring. This would at least allow you to see if the compressor engages as it should and generates pressure.

If you are using 12 oz. cans, how many did you put in the system? This should give you a rough idea if you have greatly overcharged it (which I doubt you have).

that's a good idea... I put in close to 2 12 oz cans

 

[SteveH]

I suspect you are not overcharged with that amount, and that something else is amiss. Perhaps the low pressure cutoff switch is malfunctioning (open all the time) and preventing 12v from making it to the compressor? The FSM might have useful troubleshooting steps.

 

[runthejoules]

I suspect you are not overcharged with that amount, and that something else is amiss. Perhaps the low pressure cutoff switch is malfunctioning (open all the time) and preventing 12v from making it to the compressor? The FSM might have useful troubleshooting steps.

isn't there a way to bypass that switch?

 

[1972FJ55]

The switch is in the evaporator case, so not easy to access. Have you checked to see if you have 12 volts at the compressor when the A/C is on? You said 22 psi on the low side, what is the high side?

 

[runthejoules]

The switch is in the evaporator case, so not easy to access. Have you checked to see if you have 12 volts at the compressor when the A/C is on? You said 22 psi on the low side, what is the high side?

high side is still around 50... for the few moments that it did kick on during the initial fill of r134 the high side never went very high but the low side was dropping as the engine revved. But at some point while I continued to fill it stopped working and now I can't get it to kick on even after we relieved the pressure on the low side down to 22...

 

[1972FJ55]

So you're aiming for roughly 30 on the low side and 200 on the high side so my guess is it's undercharged. I would try to put in more refrigerant. You may need to run 12v directly to the compressor to engage it to pull in more refrigerant.

 

[tmxmotorsports]

I use just over two 12 oz cans of 134a to charge

 

[runthejoules]

some progress... 12v straight to the compressor kicked it on, it took some more 134 and got cold. But it wont cycle on without that 12v... so I’m thinking that leads to a faulty amplifier. Is there a way to troubleshoot that thing or do I just need a new one?

 

[joebattle1]

Amplifier issue?

The A/C Amp Thread

This thread is all about FJ60/FJ62 A/C amplifiers. You know, that little black box that mounts on the evaporator case behind the glove box. There are plenty of other threads concerning A/C amps and I thought about adding to those, but in the end decided that the information here breaks enough...

forum.ih8mud.com

The AC Master has spoken...

 

[tmxmotorsports]

The AC Master has spoken...

What did I say?

 

[runthejoules]

still trouble shooting... with the truck at idle and the switch depressed to "on" I get no reading when I touch a voltmeter to the solder joints on the back of the switch. Fuse is good... bad switch?

 

[1972FJ55]

You may need to run the engine up to 12-1500 rpm to have the amplifier pass power to the switch. Then you could try this:
If there's just two terminals on the back of the switch, just use a jumper wire to connect them and if the compressor kicks on, the switch is bad.