Forum:
I'm trying to locate a shortcircuit in the Gauge wiring of my 'new' '99 Fourtrak F78. Keeps blowing fuse the moment the engine fires. Fuse cover shows it is 7.5A. Current measured with Ig switch on ON is 650mA. Increases to 750mA when glow plug relay switches on and 20A+ when IG on START. Have checked the service manual but still unclear about what draws current when.
Could someone please explain the start-up sequence of the engine?
Wired
Sounds like someone has wired the vehicle incorrectly and the starter solonoid is wired into the same circuit as the gauges. As soon as the starter is activated it will draw a significant current for a short time to energise the starter solonoid.
Would suggest following all the wires individually to source, the most likely being at the fusebox where you will most likely find a wire spliced into the gauge circuit.
Your ignition switch sequence os off - accessories - ignition on/glowplug relay energised - start.
Gauge Fuse
Thanks assassin.
Should have thought of it myself and check. Have to say though it blew when the engine fires after being cranked a few revs or so and so suspected some other contact. With lights, fan, radio etc. all off, what is powered up in engine compartment besides glow relay and starter solenoid? Would also like to check rev counter transducer but not sure where it's located?
Powered
Items powered up are: alternator, starter, glow plug relay, tacho transducer, all gauges such as fuel, temp etc, basically all vehicle systems.
Another possibility is an internal defect on the alternator, this is a three phase item, if the rectifier pack is faulty it may not regulate correctly and give a power surge.
Gauge Fuse Fixed
Problem sorted out
- tapping central locking control unit and connector in drivers footwell caused current surge across Gauge fuse terminals with engine running. Must be bad connection in control unit connector which happens during engine startup vibration or right foot touching loom.
I uncovered the wiring on throttle sidewall and insulated loom in sandwitch made up of duct tape and thoroughly stuck to it to sidewall to prevent movement. Seems O.K. now Thanks!