Sulfuric acid fumes. Should one breathe them in for hours ??

john matthews · Post by **john matthews** » Tue Jun 01, 2004 12:22 am

I thought I've had petrol fumes backdrafting into to the cockpit for a while now. Turns out my nearside battery has been cooking itself silly and filling the cabin with battery acid fumes. Nice.

I had the alternator out and checked last year because I could tell the batteries had been overcharging from stains on them , and because I was suspicious that it had had two new batteries recently too. Turned out the alternator was indeed goosed and the autoelectric place overhauled it.

Now it seems I'm back there again , although only the nearside battery is affected this time. Once the bubbling and boiling had died away ( took a long while ) I reconnected the batteries , and all seems fine without the car running. There's sufficient charge to start the car , no bother.

Could it be something else ? Is something killing my alternator regulators ? Is the regulator even on the alternator , or is it hiding somewhere in the recesses of my 911 muttering dark thoughts and curses to itself ?

Currently at work in the middle of the night with only a bodger's wrench by way of tools ( when will I learn to carry a toolkit ? ) , wondering if I'll get home tomorrow without being overcome on the M6 ...

Lightweight_911 · Post by **Lightweight_911** » Tue Jun 01, 2004 12:52 am

Quite possibly the voltage regulator is at fault since, as its name suggests, it controls the level of voltage being put back into the batteries.

With the engine off the voltage at the battery should be approx 12 volts rising to 13.5-14.5 volts at 2000rpm - anything significantly higher usually indicates a faulty (or failed) regulator.

All early 911's originally had separate regulators - if you need to buy a replacement make sure it's matched to your alternator. Check the make (there were at least 3 different makes used - Bosch, SEV-Marchal & Motorola) & model of alternator currently installed as it's fairly likely that it will have been changed at least once in the past 32 years !

john matthews · Post by **john matthews** » Tue Jun 01, 2004 1:02 am

Where's the regulator Andy ? on the alternator ? tucked away somewhere else ? , I thought I'd had it replaced when the alternator was out at the electrical place. If they didn't replace it , it would explain a lot ...

PS Don't some people ever sleep ?!

Robster · Post by **Robster** » Tue Jun 01, 2004 8:21 am

Yep,

lightweight 911 is absolutely right. Your regulator is goosed. The regulator limts the charge current that is fed into your battery. Too much current accelerates the chemical reaction in the battery, and hence basically boils the electrolyte in the battery. worst case scenario is that the batterry case expands and splits spilling hot acid all over the battery location - or they catch fire!

good luck.
Robster

Nige · Post by **Nige** » Tue Jun 01, 2004 10:16 am

before you replace your regulator, check that its earthed properly, I went around the garden path about 3-4 times with the same over charging problem. I replaced the regulator, had the alternator rebuilt and it still overcharged, turned out in the end that the ali cage that the regulator sits on in the engine compartment wasn't earthing properly so the regulator couldn't work properly. Abit of a rub down and lube and it all worked properly, could have saved myself alot and time and effort and cash! derrrr

Lightweight_911 · Post by **Lightweight_911** » Tue Jun 01, 2004 10:33 am

The regulator is in the engine compartment on (or near) the relay board on the lh side.

john matthews · Post by **john matthews** » Tue Jun 01, 2004 10:44 am

You are all very wonderful people , two hours kip and I'm on it.
Got home from work without a gassing btw.
I'll let you know how I got on.

Cheers !

john matthews · Post by **john matthews** » Tue Jun 01, 2004 9:08 pm

Cleaned out both battery boxes with bicarb of soda ( clearly a special twincarb soda setup ) and I think I identified the regulator - an aluminium box next to the CDI ? Fixed up a new earth etc for it but I'm still charging at 19.5V.

Pretty happy really , at least I know what's wrong and that's half the battle most times. Thanks for your help guys. Next move , change the regulator ?

Cheers all

John M

FraserMurray · Post by **FraserMurray** » Wed Jun 02, 2004 9:16 pm

Lightweight_911 wrote:Quite possibly the voltage regulator is at fault since, as its name suggests, it controls the level of voltage being put back into the batteries.

With the engine off the voltage at the battery should be approx 12 volts rising to 13.5-14.5 volts at 2000rpm - anything significantly higher usually indicates a faulty (or failed) regulator.

Ok this thread got me a bit paranoid and convinced that my battery was overcharging and that the occasional strange smell I get in the car is sulphuric acid! Checked with a pocket meter after driving the car home and the charge was 14.5V which has now a few hours later come down to 13.2V - is this within the realms of normality? There looks to be a little acidic moisture round one of the cells. The wires on the terminals are really old and crudy looking but there are no obvious problems with the wiring of the regulator. Am I worrying unnecessarily or is this overcharging significant?

Berny · Post by **Berny** » Wed Jun 02, 2004 10:32 pm

Hi Fraser your voltage looks fine try it with the headlights on and run for a couple of mins but would think its ok.

FraserMurray · Post by **FraserMurray** » Thu Jun 03, 2004 8:14 am

Cheers Berny,
I'll give that a try. Just a wee paranoid moment from me!

F

DDK - Die Deutschen Klassiker

Sulfuric acid fumes. Should one breathe them in for hours ??

Sulfuric acid fumes. Should one breathe them in for hours ??

Regulator woes