6th Generation Civic In the years from 1996 to 2000 Honda released it's 6th Generation Civic. Chassis codes: EK9, EK4, EK3, EJ6, EJ8, EJ9, EM1

A/C Charging - Which measurement to follow?

Old 07-17-2015
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A/C Charging - Which measurement to follow?

I had to evacuate the A/C system on my '94 Accord recently and when I charged the system with freon, the measurements wouldn't line up. The manual states that my car should use 600-650g of freon. However, by the time I unloaded one can containing 396g of R134a, the High pressure reading on my manifold showed that it was already at the upper bound given ambient temperature. Moreover, the Low pressure reading was about 5psi below the lower bound.

I'm really confused about this. Which measurement should I follow in such a situation?
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Old 07-17-2015
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Re: A/C Charging - Which measurement to follow?

Pressures in an operating automotive AC system are huge variables, so instead of specific pressures there are ranges that are acceptable for a given set of conditions.

I'd charge it to the spec weight of freon and see what happens.

Make sure the radiator fans run and run good
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Old 07-18-2015
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Re: A/C Charging - Which measurement to follow?

I charged up the system to weight spec and the high pressure reading was almost 400psi at ~85F. Low pressure reading was also above upper bound. These readings are in stark contrast to my 2000 Civic Si (recharged both cars back-to-back) which had both pressure readings below their lower bounds.

Another thing I noticed was that the High pressure hose was very hot on the Accord and when I tried to pull off the connector, there was a burst of high pressure air.

Any clue what's going on? Radiator fans work fine as far as I'm aware (car has never overheated even on really hot days).
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Old 07-18-2015
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Re: A/C Charging - Which measurement to follow?

400 operating sounds far too high.

Has the system capacity been reduced (based on internal volume) through use of aftermarket parts (usually the condenser) or maybe excess oil in the system?

Internal blockage due to a previous compressor failure?

Last edited by ezone; 07-18-2015 at 02:52 PM.
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Old 07-18-2015
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Re: A/C Charging - Which measurement to follow?

To my knowledge, everything in the A/C system is stock. When I first got the car, there was no freon in the system so I topped it up and the compressor clutch kicked on as it should. However, the freon leaked out so I used one of those "A/C leak fixes" and it seemed to fix the leak (held freon for a few months without issue). However, at the time, I didn't use a manifold gauge set or measure the weight of freon I put in.

I chose to evacuate and recharge the system because the A/C wasn't particularly cold (has never been). I figured I'd try putting in the correct amount of freon and hopefully the A/C would blow cold. Instead, I got 400 psi on the High pressure reading.

Bummer...
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Old 07-18-2015
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Re: A/C Charging - Which measurement to follow?

Originally Posted by ezone View Post
Internal blockage due to a previous compressor failure?
Originally Posted by cukaracha View Post
so I used one of those "A/C leak fixes"
Internal blockage due to stop leak sealant?

Just a thought.

Any idea what type of stop leak it was?
There are some that attempt to swell the rubber O ring seals, and there are others that harden and set up upon contact with moisture.


Thought on excess oil...
If someone before you had been dumping cans of freon in the system, and each can contains some amount of oil, then eventually it could end up with a whole lot of oil in it..... and this could reduce available system volume, which could (in my mind) cause high pressures.
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Old 07-19-2015
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Re: A/C Charging - Which measurement to follow?

I wasn't paying attention to the type of leak sealant so I wouldn't be able to tell you, unfortunately.

From the time that I've owned this car, there's been a total of four cans of freon that I've used (first one leaked out, second one after fixing the leak, and last two from most recent evacuating/recharge). Could this introduce enough excessive oil such that 600-ish grams of freon is in effect overfilling the system?


UPDATE: I hooked up my manifold gauge set and turned on the A/C to max setting. It looks like the Low pressure reading reaches a steady state pretty quickly and then slowly rises by about 5psi and stays there (about in the middle of the acceptable range). However, the High pressure seems to rise consistently and stabilizes around 80psi above the upper bound of the acceptable range. The Low pressure stabilizes a couple of minutes before the High pressure reading does.

Last edited by cukaracha; 07-19-2015 at 11:46 AM.
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Old 07-19-2015
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Re: A/C Charging - Which measurement to follow?

Could this introduce enough excessive oil such that 600-ish grams of freon is in effect overfilling the system?
You don't know what happened before you obtained the car though. It was empty due to leakage when you got the car, someone before you could have dumped many cans in.

UPDATE:
Have you looked at the condition of the condenser??

Many miles and years of getting hit with road debris can damage the thin little fins, folding them flat so little air can pass through them

Road salt erodes the fins and they detach from the tubes,

and bugs eventually clog the fins

All these lead to inability to transfer heat, contributing to excessive high side readings



Spray water (garden hose) on the condenser and see if that brings the high side down a lot.
What happens if you remove enough freon to get the pressures right?
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Old 07-19-2015
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Re: A/C Charging - Which measurement to follow?

The condenser looks about as crusty as the rest of the car, so it's hard to say. I don't have a garden hose to use, unfortunately. I have an inadequate mister, if that works? Haha!

I wouldn't be surprised if someone before me put in more freon that eventually leaked out by the time I got the car. Approximately how many cans do you think it would take to get a substantial amount of oil in the system?

I tried evacuating some of the freon. In order to lower the High side pressure to the upper bound, the Low pressure reading is about 5-8psi below its lower bound. I then charged it up slightly to increase the Low pressure reading to its lower bound, and now the High pressure is about 25psi above the upper bound. This process was done out in the sun (no shade).
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Old 07-19-2015
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Re: A/C Charging - Which measurement to follow?

I have an inadequate mister, if that works? Haha!
If you can get enough water on it to help cool it down
Approximately how many cans do you think it would take to get a substantial amount of oil in the system?
I don't ever deal with cans, I don't know how much oil is in one. 2oz per can would add up quick though.


I tried evacuating some of the freon
Did this help vent temperatures?

What kind of vent temps are you getting, anyway?
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Old 07-19-2015
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Re: A/C Charging - Which measurement to follow?

I can check the vent temperature now with the High pressure 25psi above the upper bound, but I don't have a "before" temperature to compare it to (I was too afraid that something might explode when the pressure was 400psi, so I didn't run the A/C).

But suffice to say that it was never very cold. The air in my Civic (which I recharged back-to-back with the Accord) is much much colder.
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Old 07-20-2015
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Re: A/C Charging - Which measurement to follow?

Originally Posted by ezone View Post


Have you looked at the condition of the condenser??

Many miles and years of getting hit with road debris can damage the thin little fins, folding them flat so little air can pass through them

Road salt erodes the fins and they detach from the tubes,

and bugs eventually clog the fins

All these lead to inability to transfer heat, contributing to excessive high side readings
Pic of a condenser removed from a 2007 Fit with 250k miles on it




The damaged fins were almost all you could see when looking through the front bumper openings
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Old 07-23-2015
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Re: A/C Charging - Which measurement to follow?

It's been about a week since I left the Low pressure at the lower bound and High pressure about 25psi above the upper bound, and so far so good. A/C isn't ice cold at 90F, but by and large it's pretty cool.

Thanks again, ezone!! This has been a great learning experience.
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