Automotive Air Conditioning Information Forum

The R134a label on my truck ('98 tacoma) has a 'min' and 'max' value for charge weight:
min: 550g (1.21 lbs)
max: 650g (1.43 lbs)
- so, the mid-point would be 600g (1.32 lbs).

When charging by weight, which value should I try to aim for? min, max, or the midpoint value? Will the amount of refrigerant within this range affect performance? For example, would I get better cooling the closer I can get to one of these values (min, mid, max)? Or, would the system's performance be basically the same anywhere within this range?

(FYI, I attached my r134a sticker just in case anyone ever needs it for a 1998 Tacoma V6 xtra cab)

The mean of 600 grams would be a good target.


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I would like to add a few thoughts to this discussion.

The A/C system in your '98 Toyota Tacoma has been designed to run with between 550 grams (19.4 ounces) and 650 grams (22.9 ounces) of refrigerant per the under-hood decal. So an "actual" R-134a charge anywhere within that range, including the midpoint of 600 grams (21.2 ounces), will meet the manufacturer's specifications.

I say "actual" because if you charge it to the minimum or midpoint amount of 600 grams (21.2 ounces), you'll need to remember to draw into the system (through the low side) the refrigerant that remains in the Manifold Gauge Set and hoses once you stop the charging operation. Otherwise, the total charge amount will be slightly less to measurably less than the specified minimum.

Depending on the length of the hoses, the MGS and hoses together reportedly can hold up to 57 grams (2 ounces) of refrigerant for a hose-set length of six feet.

How to go about drawing into the system the refrigerant that remains in the MGS and hoses has been discussed a few times in this Forum.

Point well taken, John

Most of us drain the high side hose back to the system when we are done.

So for fun I just charged my 6 foot high side hose on the gauge set with liquid. 36.5 grams according to my charging scale.

One some of the newer, smaller systems 36 grams can make a difference.

So I guess I should qualify my statement that the mean is a good target - as long as all of the weighed refrigerant actually goes in to the system.

bohica2xo wrote: ↑Wed Sep 13, 2023 8:36 am So for fun I just charged my 6 foot high side hose on the gauge set with liquid. 36.5 grams according to my charging scale.

Very interesting. Appreciate your taking the time to do that measurement.

Yes very interesting since when I did that a few years ago I got 2 oz.
36 gms is 1.25 oz.

Old residential hoses with a .250 bore I bet.

4000 psi Imperial stuff is .187 bore nominal.