18/01/2026
🚛 Volvo FH4 – Intermittent Electrical Faults 🚛
Bit of a curve ball on this one.
Truck came in with a mix of intermittent faults including:
• Trailer ABS
• Rear suspension solenoid
• OSR tail lamp
Initial checks found some corrosion in the fuse box, but nothing that screamed “this is it”.
Further inspection then found a heavily corroded wire above the rear axle, which looked like it was the culprit.
After repairs, the truck was left running and the suspension operated, but another fault then appeared. At one point it even logged a DACU fault, which didn’t help matters.
More digging eventually found a second broken wire near the EBS ECU — part of the wiring for the RCIOM. I’ve never understood why they send the power wires up and then back down, but it was clearly part of the problem.
Both wiring faults repaired and connections sorted, finally getting to the root cause.
Just shows how intermittent electrical faults can have more than one issue hiding, and why proper testing matters.
📍 Based in Cambridgeshire, covering surrounding areas
📞 If you need HGV electrical diagnostics or repairs, feel free to message or call 👍
