Electrical Help - '03 Birkin S3

[sdaddy]

I'm trying to troubleshoot an electrical problem with my '03 Birkin S3. The battery goes dead when sitting a few hours. The tach jumps around if the parking lights are turned on. The amp meter runs between 5 and 10 when ever the car is running without lights or anything on (even when the battery is fully charged)

 

1) Any ideas where I can get the correct version of a wiring diagram? (older versions seem to be around)

 

2) The relays all seem to have one ground and two non grounded wires. It would be great if someone can explain the principle of activating the relay to me - sorry I'm not knowledgable.

 

3) At best, the ohms between the positive and negative battery wires (with battery unhooked) are about 250K. I think this is low and might be OK. Can someone confirm?

 

Thanks!!

Edited July 27, 2014 by sdaddy

[jlumba81]

What's the charging voltage? Also what is the battery voltage with engine off? Good charging voltage should be around 13-14.5 volts and a good battery should be around 12.6 volts.

[toedrag]

...It would be great if someone can explain the principle of activating the relay to me - sorry I'm not knowledgable.

 

Relays are simply electronically activated switches. Instead of your finger pushing a physical button to close the switch contacts, electric current is used to close the switch contacts.

 

One half of an automotive mechanical relay is the coil side. The coil must be energized in order to close the switch contacts on the other side of the relay. To energize the coil, you simply need current flowing through it.

 

The main application for relays is to relocate the high current carrying circuitry away from where you may not want it. For example, if you have a fan that requires 30 amps, you may not want to put a beefy 30 A switch on your dash. You can put a tiny switch on your dash that handles much lower amperage, say 0.1 A, and allow that switch to drive the coil side of a 30A relay, and then the 30A of current for the fan flows through the relay and on to the fan. Functionally (not schematically), it could look like this:

 

12V -- dash switch -- relay -- device/appliance

 

Relays don't really have the concept of "inputs" and "outputs" on their terminals, btw. They also have multiple configurations: single pole, single throw (SPST) is the most basic relay and has 2 coil terminals & 2 switch terminals. A single pole, double throw (SPDT) relay will have 2 coil terminals and 3 switch terminals where one terminal is normally closed and the other is normally open, and when the coil is energized, they swap positions.

 

Besides mechanical relays, you can have solid state relays, optical relays, and others.

 

For more info, this site has a pretty good writeup:

[url=http://www.mp3car.com/the-faq-emporium/117895-faq-relays-how-they-work-and-how-to-wire-it-up.html][/url]http://www.mp3car.com/the-faq-emporium/117895-faq-relays-how-they-work-and-how-to-wire-it-up.html

[xcarguy]

sdaddy,

 

To help illustrate what toedrag is relaying (yep, a little pun in there ), here is a simple diagram of a headlight circuit using a relay.

 

 

. . . . . :cheers:

[sdaddy]

Thanks for the info! Not sure of the battery and charging voltage. The battery holds a charge fine for weeks when it's disconnected so it's in good shape and it stays charged while the car is running, so the alternator is working. What's throwing me off on the relays is that there seem to be only three terminals, not four as described. Thanks again for the help and other ideas and/or a wiring diagram are greatly appreciated!

[toedrag]

What's throwing me off on the relays is that there seem to be only three terminals, not four as described.!

 

That can be done when there is a common internal connection between the coil & switch contacts. In fact, it's not uncommon to see that done externally with a 4-terminal relay.

 

http://www.autoshop101.com/trainmodules/relays/relimages/relay%203%20pin.gif

[sdaddy]

That can be done when there is a common internal connection between the coil & switch contacts. In fact, it's not uncommon to see that done externally with a 4-terminal relay.

 

Got it. Thanks!

[rich]

Years ago I traced down an alternator with a shorted diode that was draining the battery, that was before all of the modern electronics that draw current when the car is turned off.

However, this still could be useful.

Disconnect the ground lead of the battery and place a multimeter (set to the highest millamps range) between the ground lead and the battery terminal. An inexpensive (Radio Shack type analog multimeter would be the best.

A current reading likely will be shown. Note, if you have a very high current draw, it can damage the meter or meter's internal fuse. Start at a high range current setting and work down.

Disconnect items like the alternator and remove fuses one by one to see if the current reading decreases. This can help isolate the area of the problem.

[coffee break]

I think rich is on the problem. You could pull the alternator and take it by a auto parts shop, they have testers.

[sdaddy]

I think rich is on the problem. You could pull the alternator and take it by a auto parts shop, they have testers.

 

Thanks. On my way now. The resistance from ground to positive terminal of the alternator is 100K ohms.... not enough, I'm pretty sure. Even without the alternator in the car, the emergency flasher circuit is shorting somewhere. Fuse in, only 12K ohms across the terminal wires of the battery. Fuse out, infinity.