2006 tripac apu 7.5 fuse blowing, what could be?

hi
My 2006 tripac apu keeps blowing the 7.5A fuse that is located under the bed next to the blackbox. That fuse is together with another 2 fuses (picture attached)
I now changed the fuse to 15A (blue) and now the fuse last about a week before blowing out again
I was wondering if anyone had this problem before and could tell me what is this fuse is protecting? Fuel pump? Condensor fan? A/c compessor?
Thanks
Klinger

 

@lilillill do you have a manual?
Does the display work when it blows the fuse?

 

I don't have a copy of the manual anymore. It disappeared off my phone.

That fuse holder doesn't look familiar though. I don't recall seeing that on my 07. That truck is at home though, so I can't look.

 

Mine is a 09 and I don’t have anything like it. The best thing would be to trace the wires.

 

7.5 amp... might be for one of the fans. I'd check the amp draw on the fans. I know they issued a service bulletin for upping the fuse amperage on the condenser fan, but I can't find the info on that either.

 

Yes I have the operational manual, but it does not shows anything about fuses.
Yes display works after fuse blow with "ACS" message and red led "system fault"
I noticed that with the fuse blowed when the apu starters all good even the condensor fan starts and just after 2 seconds it stops with that message
I was wondering if with fuse blowed the fan would start, if not i would eliminate that fan as the problem

 

Use the search function in the upper right corner. There’s several threads on that “acs” code. Mine would do that before the condenser fan finally died. @lilillill has a thread on replacement with a after market fan.

 

ACS code trips when refrigerant pressure is too low (empty) or too high (restriction or the condenser fan didn't come on or isn't moving enough air).

It can also trip when you have a bad switch that's open. 2006 might use two separate low pressure and high pressure cutout switches or it may have one binary switch on the filter drier.

Hook a set of gauges to it and watch the high side pressure. Depending on the outside temp, it shouldn't go much above 225. The condenser fan should run continuously and not vary in speed.

If the pressure is good and it sets a code anyway, you have a bad switch/s. If the pressure is too high (above 300) the condenser fan isn't moving enough air or there's a restriction somewhere in the liquid line.

Condenser fan is probably the culprit though.

 

FWIW, it is never advisable to put in a larger fuse than specified. The wiring is usually sized to the current flow requirements of the circuit. Larger fuse runs the risk of melting wires, connectors, starting a fire etc.

A dead short would blow the fuse instantly. The fact that it pops after some time tells me that the component that is in that circuit is drawing too much current. If its an electric fan motor like suggested above, it could be a short in the motor windings or a higher than normal resistance to the motor turning (ie a seizing motor shaft bushing/bearing.

 

Great advise above. I will do as suggested and post findings soon.
My apu has a binary switch on the filter/dryer
I think the problem will be the condensor fan, which is still the original oem since 2006 with almost 13.000hrs of service
Thank you so much for the help !!!!