HVAC question.

[Wounded_Fighter]

So my ac is blowing cold now that I charged it, but I'm not sure its acting correct? It fluctuates a lot on the high.

My low sits at a constant 24psi.

High goes between 165, and 245-250psi.

It is currently 75 outside for ambient reference. 

 

Thoughts?

[gogmorgo]

How long have you run it? Sometimes it takes a bit for the charge to work through the whole system.

Out of curiosity, what did you charge it with?

[Wounded_Fighter]

A can of 134a/UV to see if there is any leaks, system was low pressure. and half a can of 134a.

the system had been converted by somebody for the PO, there was a label. could not say when it was done though the information on it had long faded away.

 

I had truck running with A/C on high and COLD for a good 20-30mins throughout the process.

[Minuit]

250 psi sounds WAY high for 75 degrees ambient, and it should not fluctuate like that when the compressor is running. 165 would be within my expectations at that temperature, but nowhere near 250. Pressures that high make me think you've got a restriction in the system.

 

Do you know what was in the system before you charged it? What is your static pressure? - should be roughly the outside temperature in Fahrenheit and the same on both sides.

[Wounded_Fighter]

2 hours ago, Minuit said:

Do you know what was in the system before you charged it? What is your static pressure? - should be roughly the outside temperature in Fahrenheit and the same on both sides.

 

Unfortunately no I do not remember, I didnt think of writing anything down until it started fluctuating like that...

However it was substantially lower then what it was suppose to be at. which is why I decided to use UV initially, Possible leak?

 

I'm thinking of depressurizing the system, backing out all the Freon and disconnecting the lines to inspect for blockages... Good idea/bad idea?

[grumpiebill]

 
Unfortunately no I do not remember, I didnt think of writing anything down until it started fluctuating like that...
However it was substantially lower then what it was suppose to be at. which is why I decided to use UV initially, Possible leak?
 
I'm thinking of depressurizing the system, backing out all the Freon and disconnecting the lines to inspect for blockages... Good idea/bad idea?

Here in Florida 250 psi is not unusual at 75 degrees for several reasons. Is the vehicle in direct sun light? (Heat off the glass makes it harder to cool but the low side would also be elevated). What's the temp under hood? Elevated temps from engine and radiator make it tougher to cool the high pressure. Is this a fan clutch mechanical fan or electric fan? My initial thought is could have air in the system due to not evacuating the system (pull it down to a negative pressure). Or an over active expansion valve...

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[Minuit]

57 minutes ago, grumpiebill said:

Here in Florida 250 psi is not unusual at 75 degrees for several reasons. Is the vehicle in direct sun light? (Heat off the glass makes it harder to cool but the low side would also be elevated). What's the temp under hood? Elevated temps from engine and radiator make it tougher to cool the high pressure. Is this a fan clutch mechanical fan or electric fan? My initial thought is could have air in the system due to not evacuating the system (pull it down to a negative pressure). Or an over active expansion valve...

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Good points. I might have overreacted by saying 250psi was too high, but that level of fluctuation is definitely not ok. We need more information. As much as you can tell us.

 

Are these readings being taken on a vehicle that's been running for a long time? Is the electric fan running when the compressor kicks on? What do these "fluctuations" look like - is the gauge rapidly bouncing around between 165 and 250 or is it a more gradual movement? A video of the gauges with the system running would help.

 

Some more thoughts:

- Let the engine cool and get the truck out of direct sunlight if possible - in general, get the temperature of the system as close to ambient as possible. Take a static reading of the pressures with the truck off. For this, there is a single correct pressure that depends on the temperature. If it's any higher than that, you have contamination in the system and you have work to do.

- Spray a mist of water on the condenser and see what the high side pressure does.

- I HATE working on systems that I don't know all of the contents of. For all we know, whoever charged it last may not have vacuumed the system down and there could be a bunch of air (and therefore moisture) in the system. The only way to know for sure is to recover the system, vacuum it down to 30inHg, and start over.

- What exactly did you put in? Was it a can of pure R-134a+dye, or did it have any oil or additives in it?

[Wounded_Fighter]

2 hours ago, grumpiebill said:

Is the vehicle in direct sun light? Yes

What's the temp under hood?

Not sure, radiator temp was 200ish? I noticed the temp when the second fan kicked in automatically.

Is this a fan clutch mechanical fan or electric fan?

Dual electronic fans, one is flip switch, one is temp activated. 

 

1 hour ago, Minuit said:

 Are these readings being taken on a vehicle that's been running for a long time

Approx 20-30mins? It was definitely at running temps.

Is the electric fan running when the compressor kicks on?

Yes.

What do these "fluctuations" look like - is the gauge rapidly bouncing around between 165 and 250 or is it a more gradual movement?

gradually down, Rapid up.

A video of the gauges with the system running would help.

Will try this, it also seemed to develop a noise I'm not comfortable with either today.... so yeah video to follow after work tomorrow. 

 

Some more thoughts:

- Let the engine cool and get the truck out of direct sunlight if possible

Where I'm at, I can't unfortunately

- in general, get the temperature of the system as close to ambient as possible.

Best close to I can get is over the weekend when the truck sits.

Take a static reading of the pressures with the truck off. For this, there is a single correct pressure that depends on the temperature.

-Will note this.

If it's any higher than that, you have contamination in the system and you have work to do.

- Spray a mist of water on the condenser and see what the high side pressure does.

What should it do?

- I HATE working on systems that I don't know all of the contents of. For all we know, whoever charged it last may not have vacuumed the system down and there could be a bunch of air (and therefore moisture) in the system. The only way to know for sure is to recover the system, vacuum it down to 30inHg, and start over.

Thinking this is my best bet right now...

- What exactly did you put in? Was it a can of pure R-134a+dye, or did it have any oil or additives in it?

A can of A/C Pro 134a/w UV dye

1/2 a can of Jensens 134a

Edited in responses. Lol.

 

 

[grumpiebill]

Edited in responses. Lol.
 
 

You mentioned noise. If the compressor is hammering when pressure goes up excessively and compressor starts hammering could very well be an expansion valve going ape $#!&...I wouldn't call it a restriction because restrictions are typically constant (no fluctuations). I agree you should start with an evac and recharge. When system is in a vacuum should be for a minimum 30 minutes to allow moisture to boil away...

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[grumpiebill]

You mentioned noise. If the compressor is hammering when pressure goes up excessively and compressor starts hammering could very well be an expansion valve going ape $#!&...I wouldn't call it a restriction because restrictions are typically constant (no fluctuations). I agree you should start with an evac and recharge. When system is in a vacuum should be for a minimum 30 minutes to allow moisture to boil away...

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A good example is the one I'm servicing right now. 2014 F150. Showing 50 psi static pressure right now at 75 degrees ambient.Evacuating recovered 0, that's zero refrigerant. Its all air. Draw it down to negative pressure. Fix a leaking service port. Draw it down again. Let it sit about a half hour or so see if it loses vacuum. Add oil/dye and recharge.

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[Wounded_Fighter]

1 hour ago, grumpiebill said:

You mentioned noise. If the compressor is hammering when pressure goes up excessively and compressor starts hammering could very well be an expansion valve going ape $#!&...I wouldn't call it a restriction because restrictions are typically constant (no fluctuations). I agree you should start with an evac and recharge. When system is in a vacuum should be for a minimum 30 minutes to allow moisture to boil away...

Sent from my LG-M210 using Tapatalk
 

 

The noise started the next day which is weird, like a constant low tone hum when engaged.

Also, I have yet to hear the clutch disengage... like its always engaged. only (Click) I hear from the clutch is when i turn ac on or off

Evac and recharge is on my list to do then... but i'm thinking electrical gremlin for the clutch?

[AZJeff]

On 12/4/2018 at 9:10 AM, Wounded_Fighter said:

 

The noise started the next day which is weird, like a constant low tone hum when engaged.

Also, I have yet to hear the clutch disengage... like its always engaged. only (Click) I hear from the clutch is when i turn ac on or off

Evac and recharge is on my list to do then... but i'm thinking electrical gremlin for the clutch?

Depending on cabin temperature versus outside air temp,, the clutch could stay on for long periods.   Low charge levels also extend compressor run times.

 

As others have stated, I recommend starting over.  Evacuate the system, confirm no leaks by allowing the system to sit at 29" of vacuum for at least 30 minutes with the vacuum pump off, and then if all of that goes well, fill with the recommended charge of R134a.