Electrical issue

[Craig Greilick]

I have a 2000 Holiday Rambler Endeavor with a 3126B Cat engine and 6 speed Allison Trans., While cruising at 55 mph the transmission all of a sudden downshifted one gear and the entire dash cluster lit up all for about 1 second. Then it shifted back into 6th gear and lights on the dash cluster went out and it was fine after that. Any ideas what would cause this.
Thank you, Craig

 

[SpencerPJ]

Often times when goofy electrical things happen it's a ground. I hate trying to repair glitches like this, just break if it's a part. I would at least go over any and all ground connections from battery to chassis, etc, wiggle, clean, tighten.

 

[Mark_K5LXP]

Probably a "bad connection" but short of verifying every single one you don't have much to go on to know which one. One thing you can ponder is which event came first - did the dash reset causing the trans to shift, or vice versa? If you can get a wiring diagram you can trace through and see where things are powered from, and where control signals go. Reading up on the trans and how it shifts you might learn what would trigger a single downshift. Or that the dash and shift control has a common supply circuit. Years ago I had a car that would randomly reset like this while underway. It ultimately proved out to be the ignition switch that after 20 years or so and probably tens of thousands of operations had started to come apart, so some contacts inside would touch and some wouldn't. Catching an intermittent as you describe can be very frustrating. You kind of hope at some point it would just crap out and then you can trace it down but short of that you'll have to observe symptoms and isolate. It can also be an important clue to see what isn't affected when this happens, reducing the number of systems you have to go over.

Mark B.
Albuquerque, NM

 

[Ex-Calif]

My Jeep liberty is "known" for body harness plugs getting corroded at around 10 years.

One problem on the Jeep is a slew of anti-skid, failed 4wd, failed cruise control enunciation lights come on.

It is a hell of a thing to troubleshoot but one guy found a body harness in the driver's kick panel. Pull the plug, clean it, add some anti-corrosion to the pins and plug it back. It was an intermittent for years and after the fix hasn't happened in 5 years.

Now I am getting intermittent half the dash illumination cuts out.

Jeep electrics suck...

 

[Kirk]

I'm no mechanic but experience has taught me that things like what you experienced rarely go away forever. If that was my RV, I would keep digging to find someone who knows more about the problem before it returns, possibly to stay.

 

[Gary RV_Wizard]

The Allison shifts out of overdrive at the first sign of an electrical hiccup, so the downshift is likely a reaction rather than the cause. Like the others, I would suspect a connector or ground as the root cause, but haven't a clue which one or where. Could be in the dash, on the front bulkhead (firewall), or in the back where the main tranny controls/relays and the engine ECM reside.

Several years ago I had a loose connection to one of the tranny relays in a rear compartment. At first it just caused a downshift and lights blink somewhat like yours, but eventually shut everything down. The engine wouldn't re-start because it couldn't determine if the tranny was in gear or not. At least that made is a solid failure I could troubleshoot.

 

[Craig Greilick]

Thank you very much. I also remember that my initial season first power up. I turned on the headlights and all of the dash cluster lights flashed on and off once. The previous owner wired a secondary backup camera to the headlight switch. Sounds like a good place to start.