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  #1  
Old March 20th, 2017, 05:37 PM
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Bill Bailey
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Defender 90 200TDI Alternator

I had a bad alternator replaced it with DA1195 ( Britpart) but I was curious to know what charge everyone is pushing.
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  #2  
Old March 21st, 2017, 08:40 AM
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Bill Bailey
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So I guess where I was going with this is I upgraded from a 45amp to the 100amp and I am only seeing 12.5 with the lights on and 12.9 with the lights off. I have left the small wire disconnected as it is getting very hot when I leave it connected and I am seeing no benefit when connected. I think I have a bad alternator. Would appreciate any feedback.
Thanks
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  #3  
Old March 21st, 2017, 09:08 AM
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Quote:
Originally Posted by bbaileyga View Post
So I guess where I was going with this is I upgraded from a 45amp to the 100amp and I am only seeing 12.5 with the lights on and 12.9 with the lights off. I have left the small wire disconnected as it is getting very hot when I leave it connected and I am seeing no benefit when connected. I think I have a bad alternator. Would appreciate any feedback. Thanks
Take it to autozone or advance and get it tested. The small wire is for the dummy light no?
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  #4  
Old March 21st, 2017, 09:21 AM
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Quote:
Originally Posted by bbaileyga View Post
I have left the small wire disconnected as it is getting very hot when I leave it connected and I am seeing no benefit when connected.
It can not work with the small wire disconnected. You are just reading battery voltage. I'm a little concerned that you do not have the wiring correct. Can you provide details of how things are connected?
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  #5  
Old March 21st, 2017, 09:27 AM
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Bill Bailey
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Will try and crawl in there tonight and snap a picture. Its charging but like I said with small wire connected that wire gets very hot, heats up the connector on the Alternator as well. With it disconnected it charges but at 12.5 to 12.9.
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  #6  
Old March 21st, 2017, 09:36 AM
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12.5 to 12.9 is not charging. That is just resting battery voltage. It cannot charge with the small wire disconnected.

The other end of the wire must have a fault inside the vehicle. If everything is correct, there is no way for high current to flow through that wire. Most likely the whole problem is a short along that circuit and the alternator was never at fault. Does the charge light come on when the ignition is turned on and the engine off?
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  #7  
Old March 21st, 2017, 10:33 AM
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battery sense must be connected to charge via alternator. I would recommend manually connecting the alternator sense wire to 12V using an alligator clip for testing.
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  #8  
Old March 21st, 2017, 12:26 PM
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So I am at work right now and I will check this tonight, one thing I know for certain the Truck is a 1991 the wiring is at least that old :-) what gauges and approx length if I decide to rewire this over the weekend?
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  #9  
Old March 21st, 2017, 12:40 PM
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Quote:
Originally Posted by bbaileyga View Post
So I am at work right now and I will check this tonight, one thing I know for certain the Truck is a 1991 the wiring is at least that old :-) what gauges and approx length if I decide to rewire this over the weekend?
I am assuming you disconnected the original twin 12 gauge wires on the original plug at the alt and at the terminal where it meets with the battery wire by the starter leaving just the single small gauge wire that you say is getting hot. Then ran new thick power cable from alternator post to the starter post where the old 12 gauge wires ran. I just did this a couple weeks ago with a 75A alt, same difference though.
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  #10  
Old March 21st, 2017, 01:03 PM
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Originally Posted by bbaileyga View Post
what gauges and approx length if I decide to rewire this over the weekend?
The sense wiring is not something straightforward. YOU need to take the wiring schematic and trace the circuit and find the fault. You also need to understand how it works, so that you can troubleshoot. Start with reading the schematic and if you have questions, let us know.
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  #11  
Old March 22nd, 2017, 03:30 AM
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imho just bodge it temporarily with a length of 20 gauge wire from sense wire to switched 12v.

if you connect it directly to unswitched 12v hot, it will drain your battery.

once you bodge it and get it working, then fix it per john.

i think the bodge will help you understand how alternator wiring works.

Sent from my SM-G920P using Tapatalk
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  #12  
Old March 22nd, 2017, 12:32 PM
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Bill Bailey
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I am having trouble finding the wiring schematic, can anyone point me to one?
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  #13  
Old March 23rd, 2017, 07:34 AM
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So I will be back in town tomorrow and preparing for the what could be needed I was considering getting spare wire in case its need. should I be looking at 8 gauge 10 gauge 12 gauge automotive wire to rewire the original alternator wiring ? I am also looking for a decent wiring schematic. I have no problem tracing the wire if thats what it takes. :-) Appreciate the help Thanks!
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  #14  
Old March 23rd, 2017, 09:49 AM
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You can download the workshop manual here: pdf Land Rover Manuals | Landroverweb.com The schematics are in there.

The kit should have included the replacement larger power wire. Did it not? If for some reason, it did not, you want 4 gauge.

The sense wire can be any size. 18 or 20 gauge would be fine. Do you understand how the sense wire works?
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  #15  
Old March 24th, 2017, 11:23 AM
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Quote:
Originally Posted by Red90 View Post
You can download the workshop manual here: pdf Land Rover Manuals | Landroverweb.com The schematics are in there.

The kit should have included the replacement larger power wire. Did it not? If for some reason, it did not, you want 4 gauge.

The sense wire can be any size. 18 or 20 gauge would be fine. Do you understand how the sense wire works?
No I have not found a good explanation of the sense wire.
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  #16  
Old March 24th, 2017, 11:40 AM
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How about we start from the beginning. I'm worries that you have things connected wrong. Can you take a picture of the back of the alternator with the wires as you think they are supposed to be connected?
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  #17  
Old March 24th, 2017, 12:02 PM
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The sense wire operation is technically simple:

When voltage above some arbitrary threshold is applied to the sense wire, the alternator will charge.

When the sense wire is grounded or floats, the alternator will not charge.
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  #18  
Old March 24th, 2017, 01:09 PM
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Here try this,
Yes, the alternator light does work by a balance. When you turn on the key, 12 volts is supplied to the alternator's field windings through the idiot light. This gives an indication that the alternator's field circuit is intact, and it also provides the current to start the alternator charging. In fact, the alternator may fail to charge if that light bulb is burned out. When the engine starts and gets up to a high enough rpm for the alternator to start putting out voltage, there is a diode inside that takes some of the output voltage and featured back to the terminal that goes to the idiot light. The net result of this is that when the engine is running and up to proper rpm, the idiot light is receiving 12 volts at both ends, which means that the total voltage drop across the light is the zero volts and the light doesn't light.

The problem you're describing usually occurs when there is a break in the wire from the alternator's output terminal back to the battery, it does not have to be a complete break, a high resistance connection is quite sufficient to cause a light to come on. What is happening is that the alternator is full output voltage is getting sent to one terminal of a lightbulb, and the other end of the bulb is connected up to the battery positive terminal through the ignition switch, which is now at a lower voltage because of the voltage drop in the positive wire. This voltage drop causes the light to light, and also results in the battery charging poorly if at all. Usually when this is the case, the light will be very dim at hiatal and will get brighter as you rev the engine.

To diagnose the problem, put the positive wire of your volt meter on the alternator output terminal and the negative wire of your volt meter on the battery plus terminal. Put some load on the battery, such as lights or something, rev the engine, and see how much voltage is getting dropped between the alternator output and the battery terminal. If everything is good, it will be well under 1 volt. I suspect you will find you are dropping several volts in this wire, which indicates a breakage or high resistance connection somewhere along the wire. Pro between both ends of each section of the wire to find out where the high voltage drop is, then repair the problem when you find it. If you want to be half ass and not go through the trouble of tracing the wire, simply run a very heavy, about eight gauge or so wire from the alternator's output terminal back to the battery plus and your problem will probably be solved.

While you're checking things, put the negative terminal of your meter on the alternator case and the positive terminal of your meter on the battery minus, apply a load, and rev the engine. If you have much voltage drop here, Star checking the voltage drop from point-to-point once again until you find the problem, then repair it. If your alternator is rubber mounted, there may be a grounding strap between the alternator case and the block which needs to be present and in good condition. Also check the grounding strap between the engine and the body or battery negative. I don't suspect you have a ground side problem here, but when I've got the meter out and I'm looking into things I always check both ends of the situation.
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  #19  
Old March 24th, 2017, 08:49 PM
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To further muddy the waters. I have gone through two of those britpart alternators both failed in a different fashion and both lasted less then one year. I recommend pitching it for anything else! You could use a rrc v8 alternator in place of the stock unit. (100a I believe). I would assume you abandoned the dual 12g wires from the stock harness and used the new heavy gauge wire that came with your new alternator? The "sense" wire you are talking about is supposed to be landed on the middle terminal (D+). You also need to verify the charge light comes on with key on engine off. If not you have to figure out that problem. (Wire will have to be connected for it to work)
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  #20  
Old March 28th, 2017, 04:14 PM
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verified wiring was correct and attached sense wire still same result. Tested output of Alternator looks like I need to get another Alternator/return this one. Anyone got any part numbers other than the 100 amp upgrade from Britpart that seems to have arrived DOA. Maybe another brand 100 amp or a 65 amp?
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