A cautionary tale (alternator wiring...)

shambly · Post by **shambly** » Fri Mar 05, 2004 3:45 pm

I suffered an engine fire last weekend whilst fitting a fuel pressure regulator. The threaded fitting was leaking and with the engine shutdown I went to pull off the flexible hose and <ping> caught the alterator wire.

Fortunately I keep an extinguisher in the garage; unfortunately its powder...

Still, no major (i.e. expensive) harm done.

The cautionary tale is that the alternator wire is directly connected to the battery with a heavy gauge wire (on VW looms). No fuse. Not having a battery cut out switch I had to go into the sparking car to disconnect the battery to prevent the car from reigniting. The loom insulation was completely melted between battery and engine, but the conductor was intact, shorting the battery.

The original section of wiring loom had to be chopped out and thrown away.

I'm now rewiring my car with (1) a battery cut off switch and (2) a fuse in the alternator charge circuit at the battery end. I'd certainly recommend others review the protection they have in place from the alternator lead being knocked off or insulation being pierced/rubbed away over time.

Post by **Bootsy** » Fri Mar 05, 2004 3:50 pm

Cautinary tale indeed.

I have a fuse in the alternator charge circuit but not battery end - worth reviewing.

cubist · Post by **cubist** » Fri Mar 05, 2004 9:28 pm

Real BUMMER

Hope it doesn't take too long to get it back to it's A1 state again

Post by **Miggs** » Fri Mar 05, 2004 9:37 pm

hope you get that sorted quickly

shambly · Post by **shambly** » Tue Mar 09, 2004 9:52 am

Thanks guys,

Took me most of the Saturday, but the engine bay now has a shiny new loom, protective fuse, and cut-off switch.

Actually the fire did me a favour (!) in that the wiring is now much tidier than it was before as i've combined the Hyfire loom and car loom and re-routed it; Now I just need to make a proper bracket to hold the fuel pressure regulator....

Getting rid of the powder is proving tricker - every time I run the engine a new layer of it appears!

Luke · Post by **Luke** » Tue Mar 09, 2004 10:17 am

ok you convinced me, where can I get an FIA battery isolator the type that protect the alternator when you cut the power?

shambly · Post by **shambly** » Tue Mar 09, 2004 10:44 am

Luke,

I got mine from www.vehicle-wiring-products.co.uk who sell everything electrical you might need for your car. I've used them a number of times and they offer excellent service. The switch is not cheap at £21 though(compared for £7 for the standard switch)

You can see the wiring behind the switch in this photo. As well as the main high current switch, there are two low current switches. One is for the ignition feed (normally closed) and the second if for the vehicle wiring to have a 3 ohm load resistor (normally open) placed across it to provide a load for the alternator as the engine stops. You can just see the resistor behind the battery.

Luke · Post by **Luke** » Tue Mar 09, 2004 11:00 am

thanks Shambly, very tidy work there!

will now just have to work out where to fit the thing in my 911

g3ngs · Post by **g3ngs** » Tue Mar 09, 2004 10:36 pm

Shambly

I know your pain!!!

Exactly the same thing happened to me years ago with a Beetle engine, I hate powder extinguishers. A little goes a very long way!

Nice job looks great BTW

Mike Day · Post by **Mike Day** » Fri Mar 19, 2004 4:17 pm

Fires in any car aren't fun, but I'm glad it wasn't too serious. Top marks though for having an extinguisher handy.

Back in the 80's, when I had a 944, an acquaintance decided to change the fuel filter in his Escort. His Porsche was parked in the rear of the garage. He neglected to wait for the car to cool down or the fuel line to de-pressurise. Yes you've guessed it: fuel sprayed over the hot exhaust & the Escort was flambéed. It gets worse. Beating a hasty retreat from the flames to phone the Fire Brigade the flames took hold of the 911. The Fire Brigade saved his house but the garage & contents were gutted. Try explaining that to 3 insurance companies!

Just a note of caution with FIA battery isolators: over time they can cause a voltage drop, especially if the cable run is a long one from the battery-switch-starter. The symptoms are similar to a flat battery or dodgy starter so it can take a while to diagnose. So it's best to consider these service items, maybe every 3 - 5 years.

I'm a new boy to this forum but used to be a member of PCGB in the 80's. I now run a Caterham 7 (runs rings round 911's

) & am buying a Chesil Speedster.

Mike

Post by **Bootsy** » Fri Mar 19, 2004 4:26 pm

Welcome Mike