Thermo king apu "Error 9"

If your unit is loosing freon you may want to replace the
O-rings at the freon lines they may be worn ..

 

the other tip my apu mechanic told me the other day
is to turn the heat up to 90 once a month all summer
for 15 minutes
burn the gunk off the glow plug
"then you wont be whining when it gets cold" according to him

 

Tip # 3

if your apu had a Artic Switch - which is common it could be keeping your APU engine fan off which will also through the ENG code to fix

find fan plug - ( wire from fan to the plug in )

look for a glob of wires just behind or to the side of the FAN wire ..
This is the Artic Switch - it consists of 4 wires - ( 2 white 2 blue ) cut one of each don't matter which and then your APU Eng fan will run and not let it over heat .. These wires will sometimes be in a Wire Procter ( black ) and possibly a Clear Twisted plastic protector .. Be sure you only cut 1 of each color there are 4 wires only cut 2 one white & one blue .. This will disable the Artic switch which is useless and causes these problems ..

** note **

DO NOT cut any wire off the fan which will be 1 Blue 1 Black ( the blue could be red depending on age of unit ) .. That was just a reference to find the Artic switch .. DO NOT cut the fan wire ..

*** Note 2 **

this is for your ENG code which trips your inside breaker due to over heating ..

 

The wires are located outside the main housing Normalky near the truck frame depending on mounting method ... They are not inside the main APU box ..

forgot to mention that

 

If your APU comes on - Sputters and dies ... Check the Fuel Cylionoid easy self fix also part is roughly
$120.00 this will also throw the ENG code but Normalky will not trip breaker in the cab unless its completely gone out ..

fuel Cylinoid is located at

top cover
front of engine ( left side )
silver or black ( 2 screws in side of it )
located by the hard fuel lines in front top of engine
has 2 wires and a plug ( its a plug n play part )

to get the wires you got to pull the Air Filter off ( 2 screws )
to expose the wire plug to fit hands to reach it ..


Hope all this helps

 

I had this problem last week. mine would run for about an hour and shut down (Eng) code. I just needed a new fan now its back to running smooth.

 

I thought my fan was bad too ... Until I cut the Artic switch and BAM !! Turned right back on saved me $180.00 plus labor .. Lol