03’ International 9900i A/C not cooling well

[Rawze]

(07-15-2022 )Redland1 Wrote:  ...

Started looking around to see what I found and saw that the compressor wasn’t engaging.
...

assuming for a moment that it is similar to a Prostar ... unsure about that, but for a Prostar ...

someone can keep guessing at it and fighting it because they don't understand WHY it refuses to come on. -- WATCH MY VIDEOS!...

(assuming all the wiring/compressor, etc. is ok, and no fuses are blown) ...
Then there are only ever 2 reason it will not come on at all!!!. The high pressure sensor, or one of the 2 thermistors acting up>...

a). It can be that the high pressure switch is reporting less THAN 50-PSI PRESSURE ... I.E.> it thinks there is no refrigerant at all. --=(or more than 350-psi pressure if it is running and kicks out)==-. A bad wire or plug, or bad HP sensor can cause it to think there is no pressure.

AND/OR

b). One (or both) of the 2 thermistors at the expansion valve IS NOT READING CORRECTLY AND IS OUT OF RANGE!. -<<< THIS IS THE MOST COMMON PROBLEM ON ALL A/C SYSTEMS ON Internationals!!.. and it is a plague!.. sometimes even with brand new sensors.

it is simple as that!.

OTHERWISE.. if it is simply unhappy.. it will actualy kick on and run for exactly 10 minutes.. and get cold (or at least try to) .. then fault out -- if the thermistors are still reading incorrectly, but no enough to have it not come on at all.

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SO.. in your case.. if the high pressure switch is reporting at least 50 PSI.. THEN YOUR ISSUES ARE MOST LIKELY BAD THERMISTORS!.. AND YES, I HAVE SEEN PEOPLE BUY BRAND NEW ONES AND THEM NOT BE UP TO SPEC.. RIGHT OUT OF THE BOX!... ESPECIALLY AFTERMARKET THERMISTORS THAT DO NOT HAVE THE INTERNATIONAL LOGO ON THE BOX.

GO GET A BRAND NEW OEM THERMISTOR ... TAKE AN OHM METER AND MEASURE ITS RESISTANCE RIGHT OUT OF THE BOX!... AND THEN GO MEASURE THE RESISTANCE OF THE 2 THAT ARE ON THE A/C SYSTEM (EVERYTHING AT OUTSIDE TEMPS, NOT RUNNING.) .. THEY SHOULD BOTH READ REALLY CLOSE TO THE SAME VALUE AS THE ONE IN THE BOX !!!!. -- THAT IS HOW YOU CHECK THEM!.

What most people find is that the new one usualy reads about 7,000 - maybe 9,000 ohms, depends on temps outside.. and one of them (or both sometimes) on the truck are reading only maybe 300 ohms or something significantly lower .. this means that it is bad!.

ALSO.. water or moisture in the wiring or plugs causes this same problem... as it shorts out the readings and causes them to read low at the cab controller.