AC no cold air pressures measured insight please (2 Viewers)

[flintknapper]

Cold engine never started after sitting over night. Engine off and connected to gauges here are the results. These are cheap Amazon gauges so accuracy is probably lacking.

View attachment 2315470

Perfect. So that will establish that your gauges are working properly. Since you have 58 psi (static pressure) that is enough to satisfy the Trinary Switch (low pressure switch) and allow the compressor to at least start. It also tells us you have some amount of liquid refrigerant in the system (but not how much).

So...let's move forward and get a can of R134a (with dye) in it, check the high and low side pressure and then let it sit overnight and see if you have any significant leaks. IF not...then you can top it off. Happy to help guide you through that if need be.

And if I am not available..there are several well qualified folks here that can help you as well.

Good job!

 

[Biga27110]

Perfect. So that will establish that your gauges are working properly. Since you have 58 psi (static pressure) that is enough to satisfy the Trinary Switch (low pressure switch) and allow the compressor to at least start. It also tells us you have some amount of liquid refrigerant in the system (but not how much).

So...let's move forward and get a can of R134a (with dye) in it, check the high and low side pressure and then let it sit overnight and see if you have any significant leaks. IF not...then you can top it off. Happy to help guide you through that if need be.

And if I am not available..there are several well qualified folks here that can help you as well.

Good job!

That's some good news. Will report back after some recharging.

 

[half k cruiser]

@Biga27110 If it will hold pressure overnight on your gauges, you may have leaky Schrader valve cores. I had frequent issues with my rig over the last year and a half, using a black light & UV dye, two different sniffers, multiple cans of R134 and could never track it down. I finally came to the conclusion that if it's holding vacuum with the gauges on it, overnight, then the only thing in the system that could be leaking would be those valves. I used Nylog blue on the threads of the new valve cores. Holding so far.

 

[Biga27110]

@Biga27110 If it will hold pressure overnight on your gauges, you may have leaky Schrader valve cores. I had frequent issues with my rig over the last year and a half, using a black light & UV dye, two different sniffers, multiple cans of R134 and could never track it down. I finally came to the conclusion that if it's holding vacuum with the gauges on it, overnight, then the only thing in the system that could be leaking would be those valves. I used Nylog blue on the threads of the new valve cores. Holding so far.

That's interesting. Did you just unscrew the valve core and install a new one?

 

[flintknapper]

@Biga27110 If it will hold pressure overnight on your gauges, you may have leaky Schrader valve cores. I had frequent issues with my rig over the last year and a half, using a black light & UV dye, two different sniffers, multiple cans of R134 and could never track it down. I finally came to the conclusion that if it's holding vacuum with the gauges on it, overnight, then the only thing in the system that could be leaking would be those valves. I used Nylog blue on the threads of the new valve cores. Holding so far.

I remember you having trouble with that. Smart of you to use the Nylog. Not many people are familiar with it...but it's a good product.

Also, when doing A/C work....you will sometimes experience a leak under 'pressure' that doesn't show up when checked under Vacuum (front seal on Compressor is notorious for this).

And Schrader valves are probably the most overlooked item in the entire system. I don't know why folks are loath to replace them...but they are.

 

[flintknapper]

That's interesting. Did you just unscrew the valve core and install a new one?

With an empty system...yes. They install just like the valve core of a tire (but are a different size).

They can be replaced on a charged system as well...using a special tool.

 

[Biga27110]

Update:

I charged the system and both front and back AC's are very cold 39-40f. Now I'll keep monitoring pressures everyday and see how bad the leak is. I noticed when I removed the plastic caps from the valves I heard some gas escape. I might have leaky valves?

 

[half k cruiser]

That's interesting. Did you just unscrew the valve core and install a new one?

Yes, discharged the system, installed the new valves with Nylog, changed out the desiccant pack, vacuumed and let sit overnight.

Also, when doing A/C work....you will sometimes experience a leak under 'pressure' that doesn't show up when checked under Vacuum (front seal on Compressor is notorious for this).

Dude........that's going to be a real bummer if that's the case.

Update:

I charged the system and both front and back AC's are very cold 39-40f. Now I'll keep monitoring pressures everyday and see how bad the leak is. I noticed when I removed the plastic caps from the valves I heard some gas escape. I might have leaky valves?

I would get a gas burp out of both hi and low pressure sides anytime I opened the caps after a day or so.

 

[Smiles]

Hey guys,

I no longer have front or rear ac but the compressor still kicks on. Rear ac never really cooled. I read as many posts on the forums as I could. I bought some guages and need help for the next step. First pic is max ac at idle showing 5psi low side. Second pic is at 2k rpm showing 0psi low side. Ambient is 75f. Im thinking I need to add r134a as my first step to see if it holds pressure, can't find any obvious leaks and see if I get cold air.

Compressor makes a little noise not sure as it's not significant and seems to work.

Sight glass shows some bubbles with AC on.

View attachment 2314423

View attachment 2314424

Pressure test and find leaks with OFN to a max pressure of 230 PSI, not 134a, 134a is classified as a 'high global warming potential' gas.

0.15mpa = 21psi, 0.25mpa =36psi, 1.37mpa = 198psi, 1.57mpa = 227psi.

Pages are from Toyota 100 series FSM.

Hope this helps.

[/
QUOTE]

 

[Biga27110]

Update: 2 weeks and still have cold air.

 

[flintknapper]

Update: 2 weeks and still have cold air.

Excellent. Thanks for the follow up.

 

[Biga27110]

An update for the record. AC still going strong not sure why it needed a recharge if there is no leak.

 

[BadReligion]

An update for the record. AC still going strong not sure why it needed a recharge if there is no leak.

It could be a really slow leak that takes a few summers before you notice any decrease in performance. These are usually not worth repairing until they get worse.. Since you now have gauges, it wouldn't be a bad idea to check pressures every summer.

Glad your AC is staying cold.

 

[ramangain]

An update for the record. AC still going strong not sure why it needed a recharge if there is no leak.

Same thing happened to my rig last summer. Filled it up, checked pressure again recently, no change.

I did notice this though last summer. AC performance degraded after I got the small pool of water in PS footwell near blower motor. Happened a few times, then AC got hot, refilled, and 100% since.

 

[flintknapper]

It could be a really slow leak that takes a few summers before you notice any decrease in performance. These are usually not worth repairing until they get worse.. Since you now have gauges, it wouldn't be a bad idea to check pressures every summer.

Glad your AC is staying cold.

^^^^

Agreed.

Not worth chasing down small leaks that only require topping off the system once every season or two.

 

[Biga27110]

I noticed something interesting today maybe someone has some insight. When i run my rear AC the front doesnt cool very well. When i turn off the rear ac it goes freezing cold. When I initially recharged my AC i dont think i had my rear ac on if that matters.

 

[Smiles]

I noticed something interesting today maybe someone has some insight. When i run my rear AC the front doesnt cool very well. When i turn off the rear ac it goes freezing cold. When I initially recharged my AC i dont think i had my rear ac on if that matters.

Yes, it matters very much. FSM tells you to charge the system with the rear A/C running.

 

[flintknapper]

Yes, it matters very much. FSM tells you to charge the system with the rear A/C running.

^^^^

I've never seen that referenced in my FSM (99 model) perhaps it exists in others. Can you cite the page and FSM where this information exists? I'm trying to imagine why it would make a difference.

Thanks

 

[Smiles]

^^^^

I've never seen that referenced in my FSM (99 model) perhaps it exists in others. Can you cite the page and FSM where this information exists? I'm trying to imagine why it would make a difference.

Thanks

Thought I might get asked that question so I'm just trying to find the page now, standby.

BTW, I am a Air Con engineer, retired (not Auto, commercial) and have been for over 40 years.

 

[flintknapper]

I noticed something interesting today maybe someone has some insight. When i run my rear AC the front doesnt cool very well. When i turn off the rear ac it goes freezing cold. When I initially recharged my AC i dont think i had my rear ac on if that matters.

I've said for years that I have found (at least on my unit) that running the rear A/C is parasitic to vent temps in the front by 5-8°F.

Also, the rear vent temps (on mine) run 10+ degrees warmer than my front vent temps. I expect this is probably normal (a disparity) owing to the different heat load back there and cabin air exchange for the rear evaporator.

But I would be interested to know how others (when actually measured) are working. I live in an especially hot and humid climate....so my A/C is taxed heavily.