NEWS | May 18, 2021

FMTVs, HMMWVs: Summer Swelter? A/C to the Rescue!

FMTV
Photo by Capt. Joseph Warren
 
This article initially appeared in PS 801 (Aug 19), p. 14-15.

Summer temps demand a lot from vehicle air conditioning systems, especially up-armored FMTVs. To get the most out of your FMTV A/C, keep it charged to the right pressure levels.

For FMTV/LMTV A1P2 models, use 3.75 LBS of refrigerant, as indicated in TM 9-2320-333-23&P (Jun 19), also known as IETM EM 0372 (Nov 18).

Although these charge weights represent a baseline, the actual psi will vary, depending on ambient temperatures. Use these charts as your guide:
 
Temperature
(°F)
HFC-134a
PSI
  Temperature
(°F)
HFC-134a
PSI
-60 21.8   55 51.1
-55 20.4 60 57.3
-50 18.7 65 63.9
-45 16.9 70 70.9
-40 14.8 75 78.4
-35 12.5 80 88.4
-30 9.8 85 94.9
-25 6.9 90 103.9
-20 3.7 95 113.5
-15 0.0 100 123.6
-10 1.9 105 134.3
-5 4.1 110 145.3
0 6.5 115 157.6
5 9.0 120 170.3
10 12.0 125 183.6
15 15.0 130 197.6
20 18.4 135 212.4
25 22.1 140 227.9
30 26.1 145 244.3
35 30.4 150 261.4
40 35.0 155 279.5
45 40.0 160 298.4
50 45.3 165 318.3
 
 
HMMWV A/C Charge Weights
 
Charge weights for HMMWV air conditioning systems are found in TM 9-2320-280-13&P (Jan 14) also known as IETM EM 0338 and TM 9-2320-387-13&P (Mar 14) also known as IETM EM 0323.
 
Here’s a chart to keep handy on hot summer days!
 
Vehicle Charge Weight *
M997 ** 2.6 lbs
Up-armored 4-seat HMMWV 3.5 lbs
Up-armored 2-seat HMMWV 1.4 lbs
M997A3 9.0 lbs
HMMWVs with front-mounted A/C 2.0 lbs

NOTES:
* In the original article, charge weights were listed in pounds (lbs) and ounces. Here they're listed in lbs to match what's found in the TM/IETM.
** The original article included M997A1 and M997A2 HMMWVs; they are no longer supported.