Volvo EC15B - Ignition on - the battery voltage brakes down to 3V

[wowe]

Hello,

the Volvo runs well, I switched it off and as I want restart it it sounds like a rattle in the ignition on position. The nois is like a empty battery when you activate the starter. But the battery if full (over 12,8V) and it braks down to 4V when the ignition is on. At first I removed one fuse by the next one at the fuse box which is located at the right console. No change. Then I removed fuse by fuse which are located near the battery - no change of the behaviour. Then I disconnected the glowsparks - no change . And I discionnected the starter cable - no change. Hm - not easy. Maybe the ignition lock has a short circuit. Because I removed on fuse by the other and the voltage breakdown never disappeared, the short circuit must be out of the systems which are secured by a fuse.
Any idea?

Regards wowe

[wowe]

the glow sparc is naturally the glow plug...

[wowe]

The problem is solved

It was only the battery. I put a current meter to the battery and saw, that there is almost no current flowing and the voltage brokes down. I donīt remember to any such a constellation, where the battery has a nc voltage over 12,6V and such a break down with a load. But the good thing is - the repair is over.

Best regards wowe

[Mattir]

It was only the battery. I put a current meter to the battery and saw, that there is almost no current flowing and the voltage brokes down. I donīt remember to any such a constellation, where the battery has a nc voltage over 12,6V and such a break down with a load. But the good thing is - the repair is over.

Best regards wowe

Hi wove,

similar thing happened to me. The engine did not start and when startting, there was a very high current from the battery. It turned out that the starter motor had short circuit to the ground. Diagnosed with a clamp ammeter and it showed over 200A. That equals 2,4kW, over 2x the nominal starter power.

Had to replace the starter.

Lesson learnt: if the voltage over the battery goes very low on start, suspect the starter motor as well.

happy diggings

[Gecko]

Apart from those listed above, an apparent low battery voltage can be due to loose battery terminals or a bit of corrosion between the post and terminal.

My sisters "great mechanic" boyfriend diagnosed her starting problems as 'old battery' and fitted a new one. After a year of it sitting idle, I fitted it my car and four years later it's still starting my diesel!

[wowe]

I checked if the taps are well conneted. Iīm an electric engineer, so I know such things.