AC no cold air pressures measured insight please (1 Viewer)

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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.

Yes, I remember you telling us that once before. Standing by.
 
^^^^

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
I do beg your pardon, it's not in the FSM it's on a sticker under the hood.

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Yes, I remember you telling us that once before. Standing by.
Sorry for repeating myself, I'm only trying to help, and reasure members that I do know what I'm talking about.

I see so many replies to questions about A/C not functioning correctly, so with regard to charging refrigerant there is a set procedure regardless of auto or commercial, and one or the most overlooked parts of the recharge is the addition of oil.

The pages below are from the FSM.

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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.
My 04 does exactly the same thing.
 
I do beg your pardon, it's not in the FSM it's on a sticker under the hood.

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Interesting. So that is affixed to the insulation under your hood?

I don't find the same sticker on mine anywhere but I wonder if it is something that was added in later years?

Do have a pic of where it is located on yours, so that others with similar year models can check?

Is your vehicle (U.S. market) or other.

Sorry for all the questions.

The reason I ask is that this could be important information to know when recharging the system, though the reason for it is not readily apparent to me.

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Sorry for repeating myself, I'm only trying to help, and reasure members that I do know what I'm talking about.

I see so many replies to questions about A/C not functioning correctly, so with regard to charging refrigerant there is a set procedure regardless of auto or commercial, and one or the most overlooked parts of the recharge is the addition of oil.

The pages below are from the FSM.

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Agreed.

Doing it 'right' the first time is key to achieving a system that works as well as it can.

Unfortunately, our aging vehicles quite often have had previous owners and the condition of the system may not be known or maintenance records do not exist.

Evacuating and recharging an empty (and flushed) system should be Child's Play for any competent technician since we know exactly what amount of oil and refrigerant to add to the system. It's when the system needs to be 'topped off' or otherwise serviced that the unknowns can present problems.

Without evacuating the system....we have no idea how much oil might be present or if there are contaminants or non-condensables in the system. An experienced A/C tech can work his way through this...but for the average DIYer this may present a stumbling block.

That said, we certainly invite those with knowledge and experience to participate and help members here in what can be a daunting task for those not familiar with A/C theory and operation.
 
Interesting. So that is affixed to the insulation under your hood?

I don't find the same sticker on mine anywhere but I wonder if it is something that was added in later years?

Do have a pic of where it is located on yours, so that others with similar year models can check?

Is your vehicle (U.S. market) or other.

Sorry for all the questions.

The reason I ask is that this could be important information to know when recharging the system, though the reason for it is not readily apparent to me.

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My 04 100 was sold in England to the first owner I am the second owner, so it must be a European market 100 series. I don't think there will be much difference in the A/C operation or layout, you are welome to ask as many questions as you like.

These are the sickers I have under the bonnet and in the engine compartment, there is no evidence of any being added or removed.

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My 04 100 was sold in England to the first owner I am the second owner, so it must be a European market 100 series. I don't think there will be much difference in the A/C operation or layout, you are welome to ask as many questions as you like.

These are the sickers I have under the bonnet and in the engine compartment, there is no evidence of any being added or removed.

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Thank you.

Interesting bit of information.

While I don't fully understand the reason for running the rear A/C when recharging....I will add it to my practices when doing so. It certainly can not hurt anything. If anything....give a better reflection (on the gauges at least) as to 'total heat load' and how the system is reacting to it. Not that it will change the recommended charge amount.

Appreciate your input and time.

Flint.
 
Thank you.

Interesting bit of information.

While I don't fully understand the reason for running the rear A/C when recharging....I will add it to my practices when doing so. It certainly can not hurt anything. If anything....give a better reflection (on the gauges at least) as to 'total heat load' and how the system is reacting to it. Not that it will change the recommended charge amount.

Appreciate your input and time.

Flint.
Your welcome, got plenty of time now I'm retired. 😁
 
Your welcome, got plenty of time now I'm retired. 😁

Retired also, but usually so busy around our property that I find myself working more now than ever before.

The difference is....I can choose when (or not) to work and I have only my Wife to answer to. ;)
 
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.

Ive found the same not sure if normal since my AC needed recharge.
 
Welp for the record I found low AC pressure today. I thought I got lucky. Are there any typical locations to look first?
 
Welp for the record I found low AC pressure today. I thought I got lucky. Are there any typical locations to look first?
Did you ever get this figured out? My ac performance suffers quite a bit in the heat of the day. Way worse than my 2000 4Runner. Shopping for guages now. Any recommendations?
 
Did you ever get this figured out? My ac performance suffers quite a bit in the heat of the day. Way worse than my 2000 4Runner. Shopping for guages now. Any recommendations?


Having a set of manifold and a way to determine the ambient temperature at the time you use them is a great start. Having the high and low side pressures and noting whether there is any 'needle flutter, etc' will greatly aid us in being able to help you.

When you have the gauges in hand let us know if you need help hooking them up or deciphering the readings.
 
Having a set of manifold and a way to determine the ambient temperature at the time you use them is a great start. Having the high and low side pressures and noting whether there is any 'needle flutter, etc' will greatly aid us in being able to help you.

When you have the gauges in hand let us know if you need help hooking them up or deciphering the readings.
Ok, got the guages and took measurements.

after running for 10 minutes, full blast with windows down.
High 177
Low 19 no flutter

2k rpm
High 175
Low 10

ambient temp 90 degrees taken with instant read thermometer.
 
Ok, got the guages and took measurements.

after running for 10 minutes, full blast with windows down.
High 177
Low 19 no flutter

2k rpm
High 175
Low 10

ambient temp 90 degrees taken with instant read thermometer.


Low on refrigerant is most likely scenario.

I would be inclined to add 10-12 ozs (slowly) and watch the gauges.

See if the pressure rises and settles at about 30-35 psi low side and 210-225 psi high side (possibly a bit higher).

Note if vent temps become cooler.
 
Low on refrigerant is most likely scenario.

I would be inclined to add 10-12 ozs (slowly) and watch the gauges.

See if the pressure rises and settles at about 30-35 psi low side and 210-225 psi high side (possibly a bit higher).

Note if vent temps become cooler.
High temp went to 250
Low went to 35
Vent temp was 50 on highest setting
41 on medium setting.
 
High temp went to 250
Low went to 35
Vent temp was 50 on highest setting
41 on medium setting.

It will be better at highway speed as more air is moving across your condenser and compressor speed increases. Drive it a couple of days and note your vent temps.

When convenient....recheck your pressures to see if you have any significant refrigerant loss (visually check for leaks as well). Refrigerants are not 'consumables' (like engine oil) so the only way for you to have lost any is through leakage. Not a big deal if a small leak.

Now that you have gauges you can 'top off' the system periodically if you have a slow leak (system only needs attention once a year or so). Anything greater....you'll want to find the leak(s).

Let us know what you find. If no bad leaks....there are few things you can do to improve the performance of the system. We can discuss those.

You might find that it is already acceptable but I imagine it gets pretty hot and humid in your area....so just post back when you have time.
 

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