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1970-1995 Range Rover Classic
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Discussion Starter #1
As I try and work through the issues with my newly acquired 1991 RRC, I am now up to the instrument cluster where I had a tach that wasn't working, an ignition warning light that is always on (very dim at low RPMs brighter at higher RPMs) and a gas guage that always is reading empty.

I threw in a new battery and still had all the issues so I started to trouble shoot. Turns out the wiring on the back of the alternator seemed wrong to me - one of the suppressors was hooked to the sensing terminal and not the + suppression terminal. I rewired per my diagram below:
Screen Shot 2018-03-25 at 7.04.05 PM.png
When I started up the tach was working, but still have the ignition light. I tested the output on the alternator, good voltage and amps as I put on a load so everything there seems to be working as it should (I have been driving the car without any issues.) I cleaned the grounds for the instrument cluster which I believe are the ones under the air filter but still ahve the light which goes from dim to bright with RPMs.

As for the gas gauge, I'm assuming that the sender probably needs to be replaced...

Does anyone have any other suggestions?

Thanks in advance!
 

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348 Posts
Well I am in the process of resurrecting a 1984 RRC and it had a dim IGN light, slightly brighter at low RPM. Yes it had reasonable (raised) voltage at running. I was suspicions as the car came wight a whol bunch of parts including a non-fitting new alternator.

I have so much to work on that I just bit the bullet I just bought a Bosch replacement $200. took 15min to fit and IGN light is out and voltage is higher (14.4)

If one of the diodes fails it sort of half works.
 

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1995-2002 Range Rover Classic
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1,413 Posts
As I try and work through the issues with my newly acquired 1991 RRC, I am now up to the instrument cluster where I had a tach that wasn't working, an ignition warning light that is always on (very dim at low RPMs brighter at higher RPMs) and a gas guage that always is reading empty.

I threw in a new battery and still had all the issues so I started to trouble shoot. Turns out the wiring on the back of the alternator seemed wrong to me - one of the suppressors was hooked to the sensing terminal and not the + suppression terminal. I rewired per my diagram below:
View attachment 257834
When I started up the tach was working, but still have the ignition light. I tested the output on the alternator, good voltage and amps as I put on a load so everything there seems to be working as it should (I have been driving the car without any issues.) I cleaned the grounds for the instrument cluster which I believe are the ones under the air filter but still ahve the light which goes from dim to bright with RPMs.

As for the gas gauge, I'm assuming that the sender probably needs to be replaced...

Does anyone have any other suggestions?

Thanks in advance!
defective diode pack in the alternator, replace or rebuild assembly.
 

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Registered
1970-1995 Range Rover Classic
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40 Posts
Discussion Starter #4
Thanks for the reply, and from all the threads I read it always seems to be the place that people point - I'm just confused why the light is on when it is outputting the correct voltage and amps under load. I guess it is just the mysterious nature of Lucas - I will pull the alternator and rebuild. Anyone have a good source for Lucas Alternator parts in the US?
 

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1970-1995 Range Rover Classic
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40 Posts
Discussion Starter #5
So being impatient, I ordered one of these from British Parts of Utah:
IMG_6013.JPG

I got the 100amp unit (came with a bench test result which shows 116 amps for my specific unit). It's all new, not remanufactured, and bolts straight in - couldn't be easier. Since it's new, there is no core charge, so I will rebuild the original Lucas alt at my leisure. This unit costs what most remanufactured cost (if you include the core) and is actually an upgrade so I figured it was the way to go - the guys at BPU were great to deal with and it shipped the same day.
The big thing is - no more ignition warning light!!!
Now if I can only get rid of the demon posessing my central locking system!
 
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