1988 Volvo 760 Turbo Wagon Over Charging Alternator

lummert · Post by **lummert** » 01 Dec 2009, 21:37

One question. Will a charging system that is putting out more than 16 volts at idle and 18 volts at 1500 RPM cause the electronic speedometer and odometer to run too fast? While trying to find the cause of my aftermarket stereo turning off while accelerating and coming back on while stopping I found that my alternator was putting out more than 16 volts at idle and more than 18 volts at highway speeds. By the time I figured this out my battery was ruined. I installed a Denso 80 amp alternator from a 91 Volvo 740 and a group 40R Ford type battery. Now I have normal voltages (13.99 volts) and my speedometer and odometer are now accurate. Before this the speedometer and odometer were too fast and I had blamed this on tires that are undersized.

Post by **billofdurham** » 02 Dec 2009, 11:11

With voltage like that any electronics will be affected and, possibly, killed. You have been lucky that it only killed the battery.

If you are still running the undersized tyres you can check to see the speedometer error here.

Bill.

lummert · Post by **lummert** » 02 Dec 2009, 13:15

Thanks for the reply. That link to the tire size calculator must be popular, I already have it in my favorites. About three months ago I noticed that my wipers were running faster (low speed was about as fast as normal; high speed) and I did blow a new headlamp bulb that was used twice. At the time I blamed that on the quality of the bulb (they were so called blue light and cost about $3.99 for the pair). Everything seems fine now, the radio is working fine now, it had started the turning off then back on about two months ago.