Quote Originally Posted by AK83 View Post
To see(and hear) the solenoid turn itself off, like I said earlier .. with the engine not running, turn on some electrical load(lights, vent fan, brake lights,, etc) to get the battery below 12.7v and you'll hear the clunk of the solenoid and the red light will go out.
or if you disconnect the +ve lead to the start battery that does it too!
Hi AK83, and unless the auxiliary battery is lower than the cranking battery, disconnecting the positive ( + ) lead coming from the cranking battery will have no effect on the isolator.


In most cases, except maybe while you have been camping and using the auxiliary battery to power accessories like your fridge, straight after a drive, short or long, the auxiliary battery will be in a higher state of charger and will simply backfeed through the contacts of the solenoids.


This means the input side of the isolator will still be high enough for the isolator to “THINK” the INPUT is still connected to the cranking battery and the solenoid will remain on.


The simplest way to see if the solenoid is STUCK on, is to disconnect the earth ( - ) wire going to the isolator.


Also note, there is no such abbreviation as ( +ve ) in automotive electrics. The correct abbreviations for Positive and Negative are ( + ) and ( - ).


+ve is an ELECTRONICS abbreviation, as is -ve, and their use in automotive electrical subjects can lead to the wrong info being given.