New to the forums, hoping someone can help me track down an electrical issue in my 2010 Ranger. Few months ago my radio would randomly lose power. I initially chalked it up to an old radio. However, as the days are getting shorter and i actually need my dash and headlights i have discovered that the radio is not all that loses power.

i have checked the battery and all fuses and things seem in order. When i lose interior power it is to the radio, headlights, dash lights and power door locks (from my fob). Dome light, power windows and hazards still work.

Oddly, the issue often crops up when i open/close the passenger door. Is there a common chassis ground on that side of the truck that relates to these circuits? That or something behind the interior fusebox?

i tested the voltage to the headlight fuse. Not surprisingly it is 12V when things work and 2-3V when they don’t. A little wiggle of the wiring whip usually flips it back and forth which is why i am thinking a bad ground somewhere??

Hoping someone can point me in the right direction to look next.

 

Welcome to the forum

Most likely issue is corrosion in the SJB(smart junction box) which is in(behind) the passenger side kick panel
The cab fuse box is part of the SJB
SJB is the Body Computer, anything electric in the cab or exterior lights, is run by the SJB

And they get corroded connectors

This shows you where and what the SJB is: https://www.therangerstation.com/tec...horn_mod.shtml

The larger connectors can get corrosion inside
Like this: https://i1.wp.com/sparkys-answers.co...0/DSC09929.jpg
And this: https://guide-images.cdn.ifixit.com/...WCLms5m.medium

The SJB is really the only thing those systems have in common
Could be ignition switch, but when you said "passenger door" the SJB became the prime suspect, lol

Connectors have levers on them so not hard to take off
Have some "Contact Cleaner" on hand and maybe some Q-tips

 

Thanks for the super detailed reply! I thought that could be it after scouring the forum over the weekend but confirmation is greatly appreciated. I’ll pull it apart when work and weather cooperate and post back what i find to add to the knowledge base.

 

Ok so i pulled the SJB last night. No real sign of corrosion anywhere but gave the contacts a good cleaning on each if the 4 whip connectors. Looks like C2280B (lower right) is the connector controlling the accessories that lose power.

Put everything back together and drove to work this morning. Got halfway in and the radio, dash and headlights turned off for a few minutes then turned back on.

Not sure where to chase next - bad relay?, bad fuse or connection points in the main fusebox, bad wire from box to box (hope not). I’m guessing it is not a relay issue but i’m stumped.

any ideas? Could just be I did a crappy cleaning job. :)

 

I would have bet money on SJB corrosion

Here is the power distribution for 2008 Ranger, 2010 should be the same since Ford had set Rangers end in 2011 so was not doing alot of changes
Not seeing any common circuits except the SJB control

 

I was unable to pull the SJB right out of the cab since there are 2 cable whips at the top that are pinned to the unit. Didn’t want to pull too hard and my lack of circus training prevented me from contorting in a way to see how to unpin them. Perhaps cleaning in place was not sufficient. I’ll see if i can figure out how to disconnect those 2 components tonight. I can unplug the connectors but one side of each connector is pinned to the SJB. Looks like they may just be push connectors but not sure.

From the diagrams you sent, all my trouble components route back to fuse 9 in the main box so i’ll check the seating there as well.

These are the times i really miss having a garage!!

 

So after a few months the gremlins have returned and the intermittent power outages again are impacting a few circuits. This time I was prepared with a volt meter and time to see what works and does not.

I lose power to the radio, power door lock, power mirrors, headlights and dash lights. I only get 8V across fuses 23/24/30/31/34/35 when it happens. The issue is that it is very intermittent. The voltage drop will last anywhere from a couple seconds to a couple minutes. At least this confirms the problem is with the C2280A connector or the grounding associated with it. I checked the voltage on pin 1 when the truck is off and I get ~13V. I have not yet checked pins 29 and 32 to confirm I do not have a pinched wire somewhere.

Both the connector and the front of the SJB look free of corrosion. I assume I should be taking out the SJB and checking/cleaning the back? I tried this a while ago but could not figure out how to decouple a few connections at the top. I took out all the bolts but there are 2 wire gangs that are pinned to the top of the SJB. I 'think' I can just pull the connectors off but not sure. Can someone confirm how this comes apart and if it is worth taking it out at all to clean?

The fact that it is intermittent and there is still a voltage read on the impacted circuits leads me to think it is a connection problem at the SJB and not with a ground somewhere? Does this grouping share a common ground somewhere?

Thanks again for the help. The experienced folks on this site are awesome for the novice DYIers like me.

Thank in advance for the additional help!

 

I guess I should also ask if it is worth changing or looking at the connection points for fuses 1, 3 and 5 in the BJB?

 

Yes, I would say SJB issue

Yes, you can test voltage in the Engine fuse box when voltage is low at the SJB

SJB diagrams below, power also comes from the ignition switch with key on

2008 will be same as 2010

 

Ok fun new fact for everyone. I was testing other components to see what else is impacted when I see the voltage drop. When I lost power to the radio I turned on my headlights which stayed off for a second and then came on. Surprisingly, so did the radio. Turned off my lights and kept driving for a bit. Power went out to the radio again so I turned on the light switch again and same thing. I drove the rest of the way home with the headlights on and drove in to work today with the headlights on the full trip. No issues at all with power dropping with the headlights on.

So the question is - coincidence or does power (or ground) route through the headlight switch and could I actually have a faulty headlight switch causing all the issues?

Unfortunately I need to rip apart most of the left side of the truck to get at the switch so it would be a huge fishing expedition. On the plus side maybe I just need to track down a new switch?