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Old 11-17-2012, 08:13 PM   #1
mavawreck
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Default volvo 240 exciter wiring

1992 244

Can anyone tell me what color wire is going to the battery light in the dash and which wire, if it is not the same color, is coming off it? I'm bypassing that silliness with a 13ohm resistor and installing a voltmeter.
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Old 11-18-2012, 01:40 AM   #2
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1992 244...what color wire is going to the battery light in the dash
Alternator to idiot bulb - Red

Blue to ignition key switch
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Old 11-18-2012, 03:44 PM   #3
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Awesome, thanks. So if I either replace the bulb with or wire in parallel a resistor, will that keep the exciter happy?

Also, I measured 13 ohms of resistance across the light socket, does it need 13 ohms of resistance to function or will any resistance work? Summit sells 6ohm resistors to use in LED retrofits which seem like a solution.
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Old 11-18-2012, 04:13 PM   #4
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bulb.
Leave that circuit alone...just plug in your voltmeter on its own circuit...use cigar lighter wire..or whatever has positive voltage.
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Old 11-18-2012, 04:31 PM   #5
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Leave that circuit alone...just plug in your voltmeter on its own circuit...use cigar lighter wire..or whatever has positive voltage.
The light bulb socket is acting up and causing the alternator to cut in and out. So I need to create a solution. I take it apart, clean the contacts, it will work for a few months/years then acts up again. Would like to replace it.
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Old 11-18-2012, 04:35 PM   #6
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Then fix the light bulb socket.... The exciter circuit works well. You will not add reliability by re-inventing it.
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Old 11-18-2012, 04:40 PM   #7
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Then fix the light bulb socket.... The exciter circuit works well. You will not add reliability by re-inventing it.
Can you explain how one would do that? Believe it to be in the circuit board contacts since there is little that can go wrong with the bulb. I should have clarified.

Adding a designated resistor which could be easily diagnosed and a voltmeter rather than relying on a 20 year old circuit board and light socket seems much more reliable to me.

Unless you care to elaborate?
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Old 11-18-2012, 04:50 PM   #8
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You do not need a resistor, just a signal from the ignition switch run position to the exciter terminal on the alternator. This wire needs to be capable of suppling 2 - 6 amps depending on the alternator and battery state of charge.
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Old 11-18-2012, 04:52 PM   #9
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taken from rennlist

"Ouch!

A lot of pissing for a resistor and a light bulb issue!

Dave--

In my last race car I used a beehive truck/trailer clearance light with a 57 bulb in it. No Resistor. Didn't do any fancy math or try to calculate the thermal issues with the bulb. It was big enough to see and catch the driver's attention. Big concern there was for belt failuire, since the belt drove both the alternator and the water pump. Driver wouldn't notice a problem until the car stopped running and the steam was pouring out. Use a 5A fuse in the circuit for exciter and connecting wire protection.


For those playing along at home--

The alternator self-excites once it actually starts making its own power. It just needs a kick-start and no issues after that. The internal excitation is through a silicon diode with about 0.7 volts drop. Otherwise the exciter sees battery terminal voltage. The lamp serves two purposes. One is to provide a path for initial excitation current to flow, as stated by others. Should the alternator stop prodicing power for any reason, the second feature comes into play. The lamp then sees the difference in potential between the ignition circuit on one sde, and the alternator on the other side, with the alternator statr windings isolated by diodes. Bulb illuminates. Purpose of the resistor and/or bulb is to make sure that the current in the circuit is high enough to build the initial magnetic field in the rotor to start charging when the alternator spins, yet that current needs to be low enough to protect the wiring in between when the alternator isn't making any juice but there is voltage at the exciter terminal.

IIRC. the #87 light bulb is the same oneused in the tail lights and marker lights on the 928. I buy them in boxes of ten, box lasts me a decade or more."

http://forums.rennlist.com/rennforum...-wiring-3.html

Sounds like I need to keep a bulb but I could install a separate light socket + resistor in series and still bypass the problematic dash light.
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Old 11-18-2012, 04:53 PM   #10
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Quote:
Originally Posted by vlvman View Post
You do not need a resistor, just a signal from the ignition switch run position to the exciter terminal on the alternator. This wire needs to be capable of suppling 2 - 6 amps depending on the alternator and battery state of charge.
Awesome. Plus the voltmeter which will tell me what is going on.

Thanks!
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Old 11-18-2012, 05:51 PM   #11
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Clean the contacts and call it good.

Resistance doesn't matter, it's just there to help build the electromagnetic field before the alternator is up to speed so you still have some charging at idle.
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Old 11-18-2012, 09:45 PM   #12
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Quote:
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Plus the voltmeter
Here's all you need: Digital LED Car Truck System Battery Voltmeter

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Old 11-18-2012, 09:53 PM   #13
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Quote:
Originally Posted by mavawreck View Post
So I need to create a solution..
Eureka: 1-Wire GM Alternator

1-Wire Alternator means just that... simply connect one wire from the alternator to the battery, and you're done.
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Old 11-18-2012, 10:09 PM   #14
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I'm going to stick to my plan - wire out idiot light, install voltmeter.

Thanks
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Old 11-18-2012, 10:26 PM   #15
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I'm going to stick to my plan
It's only US $4.85 for a Digital LED Voltmeter shipped....
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Old 11-19-2012, 05:41 PM   #16
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I re-wired my exciter wire setup.
The stock cluster does not work properly and the alternator would not charge.
I now have a wire running from a switched fuse (forget which one, but I could look), through a diode to the exciter terminal.
Works great.
You could modify this very easily to run a bulb, or voltmeter and not have to worry about fixing the instrument cluster.
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Old 11-19-2012, 06:26 PM   #17
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Quote:
Originally Posted by whispacloud View Post
I re-wired my exciter wire setup.
The stock cluster does not work properly and the alternator would not charge.
I now have a wire running from a switched fuse (forget which one, but I could look), through a diode to the exciter terminal.
Works great.
You could modify this very easily to run a bulb, or voltmeter and not have to worry about fixing the instrument cluster.
Thanks!
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Old 11-19-2012, 06:42 PM   #18
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In the past I've soldered wires to the circuit board to bypass dead printed circuits. Solder will stick to the circuit board just fine and all the idiot lights will illuminate before starting as intended..... The alternator will get excited.... Very easy repair.

A voltmeter? Good to do but I have it as a stand-alone that monitors battery voltage with the key on.
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Old 11-19-2012, 09:05 PM   #19
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Quote:
Originally Posted by vlvman View Post
You do not need a resistor.
I checked voltage at alternator on exciter wire, its battery voltage on 1984-244.
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Old 11-19-2012, 09:07 PM   #20
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Quote:
Originally Posted by whispacloud View Post
through a diode to the exciter terminal
What's the purpose?
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Old 11-20-2012, 02:46 AM   #21
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When the alternator "self-charges" it outputs voltage on the exciter terminal as well.
It's used as a safeguard to make sure that only the switched voltage is affecting the circuit.
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Old 11-20-2012, 09:12 AM   #22
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Quote:
Originally Posted by whispacloud View Post
switched voltage is affecting the circuit.
I must assume function of light bulb is for sensing a voltage difference between alternator's exciter terminal and bulb's voltage source.

With a voltage difference, the light bulb will light up.
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Old 11-20-2012, 11:28 AM   #23
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Quote:
Originally Posted by 84B23F View Post
I must assume function of light bulb is for sensing a voltage difference between alternator's exciter terminal and bulb's voltage source.

With a voltage difference, the light bulb will light up.
*Ding! You nailed it.
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Old 11-20-2012, 07:51 PM   #24
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Quote:
Originally Posted by whispacloud View Post
When the alternator "self-charges" it outputs voltage on the exciter terminal as well.
It's used as a safeguard to make sure that only the switched voltage is affecting the circuit.
Waste of a diode.
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Old 11-23-2012, 02:40 PM   #25
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So I ran a jumper from the red on 11 pin to the blue on 7 pin going to the #31 connector per these wiring diagrams
http://www.volvowiringdiagrams.com/v...240%201992.pdf

Is there a switchable 12v going to the fuse block that would be more ideal than another to run the voltmeter off of? Any reason why I can't just tie into the blue on the 7 pin again?
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