Over-Voltage ?

[ljpear]

Driving home tonight, suddenly the headlights became much brighter, the heater fan raced up in speed (and indicated as such on the bar display), the parking, VSC, ABS, TRC and engine management indicators all came on, and there was a noticeable buzzy "roar" from the engine area, although the engine ran normally and continued OK for the mile home.

I switched off the engine, waited until the interior light went out, then re-started the engine. At tickover all was well, but increasing revs caused the same lights to come on, going off when the revs were dropped to tickover.

The problem was sudden, with no previous indications of any problems. I've done about 60,000 miles .

I'm an Electronics Engineer, have some professional test-gear but am no expert on cars or their electronics. I'm guessing an electronics failure that has allowed the system voltage to rise too far, cusing errors to be detected in the various sub-systems like ABS, but pointers would be very much appreciated.

[t-spiritpete]

Hello,

their is a possibility that the Battery is going open circuit inside or even a loose Battery connection but I would think the voltage regulator going faulty, this is built into the alternator but can be fitted as a separate part. Test the output from the alternator at the Battery with your multimeter which should be around 12vdc with the engine stopped and rising from around 13.3vdc to14.7vdc with the engine running and revved up, stop the engine if the output goes over 15vdc.

Get this fault sorted asap as serious damage will be caused to your car if you carry on using it.

Pete.

[Heidfirst]

I had this happen on a Vauxhall Carlton whilst in the overtaking lane - except that in my case the engine quit! Much fun ...

(Vauxhall replaced the alternator under warranty)

[Airfan]

14.7 is overvoltage. It has to be up to 20% more than the original voltage. 12 * 1.2 = 14.4V top.

[t-spiritpete]

Actually some manufactures state 15v as maximum and whilst I agree 14.3vdc is a reasonable and an average output, 14.7vdc is not over voltage for a short period, if continued for a long period though over gassing will occur at above 14.3vdc and in a sealed Battery this is not great, in a vented Battery it is not such a worry but it will require topping up with de-ionised water as in times gone by or still true today for industrial batteries used on forklift trucks for example on which I worked for many years.

I think the OP has a far worse problem than 14.7vdc so lets wait for the outcome.

With due respect to your views .... Pete.

[Airfan]

I agree it won't harm the Battery much if you charge it with 15vdc for short period but I wouldn't stay calm if I constantly get 14.7 at 2000 rpm. If you travel let say 100 miles with that you'll boil the Battery and this is my personal experience unfortunately.

Edit: You won't get guarantee if the Battery store measure 14.7 vdc at 2000 rpm here in Bulgaria.

[t-spiritpete]

I agree it won't harm the battery much if you charge it with 15vdc for short period but I wouldn't stay calm if I constantly get 14.7 at 2000 rpm. If you travel let say 100 miles with that you'll boil the battery and this is my personal experience unfortunately.

Edit: You won't get guarantee if the battery store measure 14.7 vdc at 2000 rpm here in Bulgaria.

Thanks for your reply Georgi,

we haven't heard much from one of your countrymen recently , the well respected forum member and great friend ..... Igormus.

Regards

Pete.