A headscratcher

kazbanz, Jun 5, 7:48am
1997 Nissan Avenir starting/running normally.
Yesterday after being driven and turned off refused to start.
By that-- dash lit up normally radio normal,click from starter cut out in the cabin when you "hit" the brake pedal but no go.
jack car up ready to tap starter with a hammer but assistant turns the key and starter motor not clicking at all.
Dark day so reach up to wires leading to starter motor to trace them to starter-looking for loose connection etc. assistant turns key and car starts normally.
car driven to actual workshop and no loose wires found. no busted wires etc. car drives away. 5 minutes later car is back. Several dash warning lights on and the battery is hot. Alt tested and output is 18volts.
bad luck or am I missing the connection between not starting and alt overcharging.
franc123, Jun 5, 8:08am
New battery and alternator required sir.
kazbanz, Jun 5, 9:31am
Yea mate I knew that.--What has me baffled is the connection or lack of-seems weird the starter just stopping then works perfectly then 5 minutes later the alt is toast enough to cook the battery.
skin1235, Jun 5, 9:57am
starter off and dismantle, looking at brushes, brush holders and insulation or a break in the primary magnetic windings

insulation breakdown ( direct short) in the mag windings will pop diodes in milliseconds
mm12345, Jun 5, 10:13am
If the alternator diodes were borked, it wouldn't have been outputting 18v. The (internal) regulator in the alternator is borked. That might have happened quite quickly because the battery was stuffed, the alternator ran hot, and the regulator module gave up the ghost because of continuous heat.
I doubt that 18v for 5 minutes would have killed the battery. If the battery was drawing too much current, then the voltage might have been staying low enough to not light up the alternator warning light on the dash (which should light up on both under or over voltage on a Nissan of that vintage).

So replace the battery and alternator, then check to see if any starting problems remain. Could of course just disconnect the alternator, put a fully charged battery in and see if it starts - but that's a bit pointless IMO as the alternator has to come out anyway. IIRC, removing the alternator might be a bit of a prick of a job if the car has A/C - no room to drop it out underneath unless AC compressor brackets are shifted, and a real squeeze to get it out from above past the top radiator hose.
skin1235, Jun 5, 10:39am
sorry mm, the regulator is even more fragile than the main diodes, is a given that the reg will be fried ( and I never referred to it because of that, )
valid point re the diodes still being serviceable - if they were blown the battery - as you say

the question is more what caused the reg to fry, an internal short in the shunts will cook it real quick
you can repair or replace the alt, but until you've checked for what caused it you'd be foolish to just jam a charged battery in with a new alt and hit the key - you could very easily be repairing that new alt in the next hr too
skin1235, Jun 5, 10:52am
kaz, you maybe looking at the wrong system re loose connections though
the reg needs batt signature to work, that could be internal to the alt or it could be external to pickup point - if the reg doesn't get sig it just pushes max

but thats a sep issue to the starter - the soleniod uses the shunts as the earth path, if it clicks the circuit is good, then its not ( path broken,) then it is etc = broken path/circuit, cold be as simple as a loose connection at brush pole, could also be broken shunt winding either at pole or further into the shunt winding - 6mm X 2mm ali strip wound around the mag shoe, look for signs of movement - they don't usually break unless something is moving - ali doesn't like flexing

if it is then check very thoroughly the mag shoe attachment
skin1235, Jun 5, 10:55am
plus

usually when the reg fails it fails open

to pump 18 plus it has stayed closed - not open,
the reg may still be serviceable but the incorrect batt sig has to be found and rectified
mrfxit, Jun 5, 3:00pm
Seen something like this sort of crap before on a VT commodore.
Alternator cooked the cable on the back of the alternator at the same time as it almost boiled the battery BUT caused hard starting & rough idling/

Solution was to simply replace the alternator even tho it showed as charging ok & repair the cable joint.

All good after that, even the battery was ok.
bigfatmat1, Jun 5, 3:36pm
So much miss information in this thread. Start with looking at the charging fault and the battery. Test battery if its buggered replace it. Recheck charging. if charging is high at the battery, replace or repair alternator. Then look for a starting issue if no fault can be found. You can a: leave it, B: remove starter and check brushes. No click is caused by brushes as the pull in winding is earthed through the field. Also shorted diodes shorted rotor and a faulty reg can all be a cause for overcharging. A short in the starter will not bugger the alternator. The starter on this car does not have windings either it is permanant magnet.
kazbanz, Jun 5, 3:43pm
Sorrry guys-maybe Im not being clear.
Look under car and maybe a loose wire /plug unplugged in starter motor was pushed back in place by me grabbing the wires-Yep I get that.
Alt knackered--yep understand that
battery boils from excess alt output -yep I get that.
Quick fix -unplug alt and all but battery light goes out and the car starts totally normally suggesting battery isn't goosed---understand that.
What has me scratching my head is how the two events are linked.
starter not working then working normally and alt goosed
tgray, Jun 5, 3:47pm
What's a big time car dealer guy like you messing around with an 18 year old cheapie?
bigfatmat1, Jun 5, 3:54pm
becuse it didnt start and someone jumpstarted it backwards. Leave the battery and test in the morning I have seen batteries that start a vehicle the get real hot and cause the alternator to charge at full output ie high current not high voltage. then the battery gets real hot
kazbanz, Jun 5, 4:20pm
where in the name of gosh dya get the idea I'm a bigtime dealer?
kazbanz, Jun 5, 4:24pm
hey mat-thanks but definitely -100% certain no attempt at jump starting was done.
cart running totally normally pulled up. Turned off normally then 5 minutes later tried to start it and nada. -no solenoid click nothing. grabbed wires and it started normally. Did a dozen starts to be sure and back to normal.
bigfatmat1, Jun 5, 4:52pm
Hmmm can a gas and a match is needed
snoopy221, Jun 5, 4:53pm
matt me ole mate why oh why do i suspect a fried brush spring,,, or a coincidentally weak one-re kaz's query starter workie/no workie/workie?
(remember the ole siera plastic cap on brush spring-famous old plastic and starter workie/no workie/workie?)
robbos1, Jun 5, 8:42pm
My pick would be ignition wiring. the piece behind the key barrel. when you pull a plastic cover off, they have brass buttons that wear out over time and intermitantly short out.
I use to sell heaps working at a wreckers, particularly in nissans and toyotas.
kazbanz, Jun 6, 7:10am
About 10 years ago with ew in it. The car is ex wifes car.
skin1235, Jun 6, 7:22am
wasn't aware they were a fixed magnet starter, starting issue could then be another area caused, ie switch, not sure re Avenir but know the primera from that era had connection issues base of steering column, almost always the starting circuit when they played up ( look for evidence of heated connections in that multiplug base of steering column, loose spade fitting gone black) very intermittent in manifestation - works for weeks then quits, slightest nudge ( door shut/slam) and works again for a few days/weeks

why the alt overcharge - if the reg is cooked it usually fails undercharge not overcharge, overcharge means the reg is not receiving batt sig properly, the batt sig is internal to the alt but mechanical, could be corrosion at the peg,
tony9, Jun 6, 7:40am
How about the starter solenoid sticking. In the first case (no start) it is stuck out. Later it is sticking in and the starter stays engaged. It would then act as a generator and grossly overcharge. Particularly if the starter motor used field magnets.
kazbanz, Jun 18, 6:37am
Putting this one to bed.-It must have been a big ol coilncidence.
Saturday night I got a call from ew. car wouldn't start
I get there and turned the key. It started normally. hauled the starter out and-Hmm yep brushes worn to their limit.
bigfatmat1, Jun 18, 10:12am
Well done you can be thankful it wasn't 4wd otherwise you would still be pulling starter out
kazbanz, May 31, 8:04pm
Yep I thought so too -its a bad enough job as it is on axle stands