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86 745 TD - very high current drains battery

Hi all, my first time posting here, so bear with me. My trusty-but-not-rusty

745 TD, 380.000 km, did not start yesterday - something is suddenly drawing a pretty high current from the battery, even when parked, motor off, all lights etc. also off of course, and the key in my pocket. I assume either a sticking relay (of the pre-glow-plugs or the starter) or something similar (isn't there one for stopping the Diesel too?) . It is not a classical short-circuit. I measured the voltage of the battery immediately after this happened, it was down to 5.2 Volts. I removed the positive connector from the battery and reloaded it @ 4 Amps (sorry, the charger did not manage more...) , and the battery was refilled after 6 hours. So, substantial damage to the battery can hopefully be excluded (it is about 28 months old).

What can be the reason, and what can I do to heal it? The magnet that moves the starter into its active position perhaps (sorry, I am not familiar with english car-technese)?

Any suggestions what to look for (in beginners' lanaguage, please!) is appreciated. A typical weekend failure! And worst of all, our V 40 is in service for its TÜV approval. Down from two to zero cars is bad.

Thanks in advance, cheers,

Ulli.

Reply to
Ulrich G. Kliegis
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Did you actually measure the current?

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

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void _-void-_ in the obvious place

Reply to
Boris Mohar

On Sun, 03 Apr 2011 07:57:13 -0400, Boris Mohar wrote in alt.autos.volvo:

Nope, since I don't have an AmpMeter for currents as high as it is necessary to force a battery to its knees...

But I got a few hints from a german Volvo-Forum pointing at the relay for the pre-heating glow plugs. I am just about to check that.

Cheers, U.

Reply to
Ulrich G. Kliegis

On Sun, 03 Apr 2011 07:57:13 -0400, Boris Mohar wrote in alt.autos.volvo:

Now I first measured the resistance between the positive-connector (battery disconnected!) and the central contact of the glow plugs - 0 ohms. A few hearty knocks on the box that I suspect contains the relay switch - on the second knock, I heard a faint ping - and subsequently no connection any longer between batt-plus and glow plugs. Reconnected the battery, key in on-position, glow-plug light comes on, goes off, start, fine.

I'll replace the relay switch though, it seems it has had its time. Magnetic remanence is nothing to joke with if it drains your battery...

Thanks again for the comment, and keep on volving :), Cheers, U.

Reply to
Ulrich G. Kliegis

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You don't need a meter for high currents, just capable of monitoring the load that is draining the battery. This is usually just a few amps, and most multimeters can measure up to 10 Amps without any problem.

An alternate method to track down this type of problem is to disconnect the positive battery cable and connect a 12V bulb between the positive terminal and the cable. The bulb will glow as long as the fault is in place; you can then localize it to a circuit by pulling fuses one at a time until the bulb goes out. A smaller bulb, as used for a parking or marker light, works well.

Gary

Reply to
Gary Heston

On Sun, 03 Apr 2011 12:23:46 -0500, snipped-for-privacy@hiwaay.net (Gary Heston) wrote in alt.autos.volvo:

Bug with appliances like the starter or, in this case, the glow plugs, there is no fuse to pull since these draw their power directly from the battery. A diesel starter can draw up to 150 or more amps, the glow plugs also are in the 50 Amps range (mind you, this car has alone

6 of them).

As I wrote earlier, locating the faulty relay switch was comparably easy after some thinking, getting information on where to look, and low power measuring.

And the bulb method - well, I learned that about fifty years ago when first daring to set up my electric model train on my own...

Cheers, U.

Reply to
Ulrich G. Kliegis

i would have guessed the solenoid. this is all good to know. i just purchased a diesel rv/truck to pull my Volvo (r) around to races. i know that it has it has a diesel heater (glow plugs), an oil heater & a coolant heater. i bought her in MN & drove back. the first night was very cold (my -30 bag got completely zipped up) & the next morning i saw the truckers lighting fires under their engines (i let Echo idle, like many truckers). the point is cold weather & diesel do not mix.my dad was stationed in the arctic after the war. he explained how one could open a 55 gal barrel of diesel, like i sardine can and ignite the gel inside to burn slowly & safely, like sterno. the power involved is amazing. that we have electrical systems, much less batteries (the truck has 2000+ cca & 900ah) that can deal w/ this is incredible. i hope that by now Volvos have an OBDII sensor which will generate an error message.

Reply to
edasduke

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