Bolt Jr+ Trips With Unexpected End — Controller Overheating / Direct Sun¶

Summary¶

If a Bolt Jr+ repeatedly trips with an "Unexpected End" style message in very hot conditions, consider controller/base overheating. In the field case, the rig was in extreme heat, the fans had been turned off, and turning the fans back on cleared the problem.

Symptoms¶

Bolt Jr+ keeps tripping.
Error includes "Unexpected End" after a run or trip.
The base/controller is in very hot ambient conditions or direct sun.
Fault can resemble network, E-stop, or weak-connection problems.

Community Solutions¶

[CONFIRMED] Turn cooling fans back on and shade the base¶

2025-08-28 — Francisco Aguila / Simon Wakley

Check whether base/controller fans are running.
Turn fans on.
Shade the controller/base, especially when it sits at the end of the track in direct sun.
Let the base cool before continuing high-load moves.
If available, use the pendant to monitor controller temperature in degrees C.

The reporter confirmed: "It was just too hot, we turn the fans on and it's working fine."

confidence_score: 0.82

[LIKELY] If not heat, check weak E-stop connectors¶

2025-08-28 — Colin Michael Quinn

If the base is not hot, inspect DuPont connector pins in the slide-out electronics tray and gently test junctions along the E-stop circuit flow to find weak intermittent connections.

confidence_score: 0.62

Image description: Bolt Jr+ trip/error screenshot in extreme heat where the controller/base fans were off; resolved by turning fans on and cooling/shading the base. Searchable terms: Unexpected End; Bolt Jr overheating; fans turned off; controller too hot; direct sun base trip.

Media Text / Description¶

Image description: Bolt Jr+ trip/error screenshot in extreme heat where the controller/base fans were off; resolved by turning fans on and cooling/shading the base.

Media 1: Image description: Bolt Jr+ trip/error screenshot in extreme heat where the controller/base fans were off; resolved by turning fans on and cooling/shading the base. Searchable terms: Unexpected End; Bolt Jr overheating; fans turned off; controller too hot; direct sun base trip.

WhatsApp Excerpts¶

[27/8/2025, 5:35:42 pm] ~ Tobi:

[28/8/2025, 3:28:32 am] ~ Francisco Aguila: Hi guys boltjr keep tripping we are getting this error any idea?

[28/8/2025, 3:50:04 am] ~ Simon Wakley: Unexpected End means it was running a move and you stopped it, or a trip stopped it. Fast move? Network cable issues maybe, but that's a guess.

[28/8/2025, 3:57:13 am] ~ Colin Michael Quinn: Check the DuPont connector pins in the slide out electronics tray. I found an issue with mine dropping random e stops. I found it by turning the rig on and gently touching the different junctions along the e stop circuit flow until I could get it to trip. It’s likely a weak connection somewhere.

[28/8/2025, 3:57:26 am] ~ Colin Michael Quinn: