Switch box troubleshooting questions, it's doing some strange things...

[Jennifer Rose Towing]

This is a new one for me.
The short of it is that a 4 gang miller switch panel is randomly not functioning.

The lengthy version of the issues...

Sometimes the switches work and sometimes they do not.
Switch 1 activates the lightbar,
Switch 2 unable to find anything hooked to it
Switch 3 is upper work lights
Switch 4 is lower work lights

The Whelen Liberty that was on the truck only partially worked when the truck was purchased. I was asked to figure it out and add some lightheads.
I traced most of the wiring to figure out what was what as it has been worked on a lot.
The switches randomly work with no real rhyme or reason. Sometimes tapping on them will make one or 2 work. what really confuses me is when one is working, sometimes activating one of the other 3 works fine and sometimes when activating one or 2 of the other 3 all go dead. Sometimes activating a random 2nd switch will kill it all and sometimes it takes a 3rd. Ran switch 1 and 3 just fine for a bit while the next day after no changes it wouldnt function.

The switches are independent and appear to have a circuit breaker built into each switch. All 4 are fed from a single line direct from a battery to the bus bar on top of the switches. The 3 back lights for each switch have individual feed line direct to the output terminal of each switch. All I/O connections are tight. I am stumpped because one random switch or combination of switches shouldnt randomly effect another. If a switch was bad or the breaker was tripping (what are the chances that is happening to all 4) I could understand that switch shutting off but not the randomness of it all.

I did send an email to Miller asking for the specs of the switch box unit but waiting to hear back.

 

[Master X]

Seems to me, the contacts of the switches internally are going bad/not making contact. Using an ohm meter, I would measure the resistance between two terminals when the switch is on. If the ohms are high I would say the contacts internally are not making a good connection IE bad switch.

 

[jhook]

Sounds similar to my issue right now with ford upfitter switch’s screwing around . Switch 3 intermittently will work but activates switch 2 causing a flash bulb effect . Also switch 5/6 are dead I hate these ford upfitter crao.

 

[QUICKONE]

What is that loose unconnected White Wire to?

Where is the ground connected? Chassis or direct to a ground bus/Battery, (I prefer to run BOTH 12v Supply connections direct from the Battery). Sometimes I've found that corrosion or vibration will loosen the 12V neg connection that will cause intermittent gremlins.

Like the others have said. I'd meter out the switches out, starting with both the 12V + then the 12V - connections that supply the switch panel.

One quick observation is that the components are extremely dirty. Unless they're potted switches I've found dirt to prevent good conductivity inside the switch/on the contacts. I'd attempt to do a quick cleaning with some CRC Electronic Contact Cleaner or similar.

 

[Jennifer Rose Towing]

What is that loose unconnected White Wire to?

Where is the ground connected? Chassis or direct to a ground bus/Battery, (I prefer to run BOTH 12v Supply connections direct from the Battery). Sometimes I've found that corrosion or vibration will loosen the 12V neg connection that will cause intermittent gremlins.

Like the others have said. I'd meter out the switches out, starting with both the 12V + then the 12V - connections that supply the switch panel.

One quick observation is that the components are extremely dirty. Unless they're potted switches I've found dirt to prevent good conductivity inside the switch/on the contacts. I'd attempt to do a quick cleaning with some CRC Electronic Contact Cleaner or similar.

There are several lose/unconnected wires and unsure of what they do or where they go. The truck has had a lot of rewiring done and most not the best. Couple of unconnected wires in the rear harness read 4 volts when nothing was on. I was only there to upgrade lighting but the wiring was a mess all over.

I did a few quick tests on the switches. The output from the switches matched the led indicators. I presume the small black wire coming in from the side was the LED ground and backlight. Wires were short and went into larger bundles so chasing them was not something I had time or energy for. The switches should still run power as they only had an in and out terminal. Inputs were linked by the busbar and outputs were independent of eachother.