Citroen Synergie - trying to start - loud click, fails

[TJB444]

I have a Citroen Synergie 1999 TD, 170k on clock. Works fine apart from this one intermittent problem.
On attempting to start car, lights come on as expected, when go to start engine, loud click and lights go out. ....dead. Nothing when take key out and put back in again.
Battery is virtually new and fully charged.
This may happen several times, then follow same sequence and engine starts. Car will work for months with no problem and then it will go again.
I have checked battery connections (after it restarts radio etc has to be reset) and then are clean and tight. I have checked/reseated all fuses.
Seems to me as if they may be corroded connections and/or water/condensation in connections.
But where do i start?

If I knew where the "click" was coming from I could pinpoint issue (!) ...seems to be driver's side of car....I only noticed this when my wife went to start the car and I was nearby.

Any help/advice would be appreciated. .e.g. what to disconnect and clean? and how to get to connections. Thanks TJB

[Peter.N.]

Have you checked the voltage across the battery after it won't start? If the battery is OK there should still be 12 volts across it. If the lights are going out its either got to be the battery or the connections to the car somewhere. If you have volts on the connectors check from + to earth on the car and engine, could be that the earth lead is making bad connection.

The 'click' is probably the starter solenoid trying to engage and dropping out again when the current disappears.

Peter

[Richard_C]

Yes check the voltage across the battery as you try to start it.

If volts and battery connections OK, next thing to look at is earthing as Peter says. Trace the negative lead from the battery, it often leads to a big chunk of wires bolted to the bodywork somewhere, * or maybe a common connector on the back of something. Mine isn't here today to go look at it. Clean that up and see if it helps. There may be a thick earth lead from the engine block to the same point so look at the end of that as well. Often, a corroded earth connection will carry enough current to run low and medium power stuff but won't take the 'big amps' you need to turn the starter.

Also worth checking that the starter motor itself is properly bolted to the bell housing and that the bolts haven't worked loose as I think it earths through there.

* I have a sort of manual, in French with unhelpful block diagrams of electrics, but it looks like there may be an earthing point on the inner wing below but fairly close to the battery

[TJB444]

Thanks for your help.

I went home ....nothing.
I opened fuse box...in engine...reseated all fuses. checked all cables...none were loose, pushed in all connections...couldn't find any loose ones... tried engine and everything was fine.
I am as bemused as before. Doesn't appear to be any logic except that I pushed down/reseated fuses. I did move cables and checked they weren't damaged and checked all connections in case any were loose...I tidied them up as it seems after car service cables are left loose. i could not find any water ingression.

My wife has now driven the car ... on seven journeys and has had no issues....since I "fixed" the problem.

Will wait and see if same happens again

[sparksie]

Don't you just hate it when that happens?
But imagine telling a customer you've fixed nothing, but it's working now!
Take it away and call me when it fails...
That call rarely ever comes, because somebody else gets it!

[Old-Guy]

Also worth checking that the starter motor itself is properly bolted to the bell housing and that the bolts haven't worked loose as I think it earths through there.

Long, long ago I had the same problem with a (proper) mini - the problem was slight galvanic corrosion between the starter motor face and the bell-housing plus under-tight and rusty mounting bolts. Solution was to clean up and tighten up the starter motor in general. plus squirt of WD40 to repel salty spray.

* I have a sort of manual, in French with unhelpful block diagrams of electrics, but it looks like there may be an earthing point on the inner wing below but fairly close to the battery

Recently I have twice had to clean up connections to "inner wing earthing points"; the blue VSX and eldest son's Rover - poor starting and charging in both cases.