Bongo Fury

Hi Folks

Short intro to long story - central locking fob on key died on our X reg Bongo, so thought Id fit alarm/immobiliser/central locking control with fobs to resolve...have spent 11 hours trying to wire in a well(ish) know brand of unit that has a normally closed relay inline with the stater solenoid feed from the ignition switch, 87a & 30 are the starter feed switching/interup, 85 is a switched earth thru the alarm/immobiliser unit & 86 is a +ve feed.

I have the option in the destruction manual to take the feed for 86a from the ACC circuit switched feed (called low power mode) that only provides power to the relay when the ignition switch is turned to ACC or wire it via a permanent feed.

I thought I'd chose the ACC fed option - then the fun begins....relay tested & functions fine NC, Open when power applied, take relay out of circiut starter wont work, turn key to ACC relay clicks etc - all going to plan...turn key to poss 3 & starter turns/engine starts regardless of the apparent state of the relay, have earthed it independently as well to test & no change

After contemplating taking a very large hammer to everything in sight, I ve just had a thought...when the ignition switch is turned to poss 3 to start, doesnt this kill the ACC circuit to give the starter motor full battery power

If so surely this kills the feed to the relay & it goes NC - so effectively no functionality - am I clutching at straws or does this theory have some validity...if its good I think just need to power terminal 86 with a permanent un -switched feed

Please help so some faith in my DIY skills can be restored

Yes that will happen, but its not to give full power to the Starter its to stop the back EMF from the Starter blowing sensitive electronics up!
Normally devices that need to keep running for a few seconds will have sufficient reservoir capacitors to keep the unit powered, or will store the various states it needs to maintain during a power loss. Why not take the feed from a permanent source like this fuse that feeds the ECU a permanent supply;

Thanks Geoff -this will be the first task in the morning, I'll let you know how I get on...thanks for the education on EMF, I'd not thought of that before

Problem sorted - many thanks.....I have a new one now though - new post to follow!