RangeRovers.net Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
Greetings, hope you can help.

1990 Range Rover Classic in the UAE (a beauty! :mrgreen: ) - called Rhino, btw - last week exhibited all signs of extra-terrestrial interference including radio switching off and on, rpm gauge doing the can-can, lights flickering, engine misfiring, and the dreaded red battery light on the instrument cluster: yes, alternator.

Had a shop fix it and it's back on working nicely (allegedly) except the red battery light is still on and the rpm gauge did not resuscitate.

From what little I know, the rpm signal is picked up by the brown/red wire at the alternator.

Now, the alternator is a DENSO model, made in UK - and the problem lies either in the alternator itself or somewhere along the circuit all the way up to the dash.

How can I check without removing the alternator again or dismantling the entire dash!!

Thanks for any advice.
 

·
Registered
Joined
·
523 Posts
Welcome aboard.

Have you looked at the 'electrical issues' sticky thread? I think you need to find a voltmeter and go through that thread and report back.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #3
Fair enough, let me give it a go.

While I'm there, perhaps I can also measure any voltage from the alternator bolt that the rpm brown/red wire connects to, which maybe can tell me if the problem source is at the alternator.

Is it a fluctuation in voltage that works the rpm gauge? In that case, accelerating should give me a corresponding rise in voltage at the alternator bolt.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #4
Forum Posting - Posting Results:
If you haven't yet solved your problem and want help, please copy and
paste this information below into a new thread. Please fill in answers
for EVERY POINT. This is a cut down version of the above tests.

1990 Range Rover Classic, 3.9L auto, DENSO (UK) alternator.

1. Engine off, all accessories on for 30 seconds, then off. What voltage 12.50

2. Voltage across battery at idle (no electrical load) 13.90

3. Voltage across battery at 2000rpm (no electrical load) 14.00

4. Voltage across battery at 2000rpm (everything electrical switched
on) 13.75

5. Voltage at ALTERNATOR at 2000rpm (everything switched on)13.94

6. Voltage drop between alternator body and battery negative (YES
negative). Measure at max electrical load and 2000rpm .117~.124 (millivolts please)

7. Voltage drop between alternator positive and battery positive.
2000rpm, max electrical load .106~.111

8. Check Voltage drop from Battery Negative terminal to 1st
groundpoint on vehicle 0.00

9. Check voltage drop from 1st ground point to block 0.00

10. Check voltage drop from Alternator Housing to block 0.00

Also:
-What are your symptoms: after repairing alternator, rpm gauge not working and red battery warning light on full.

-What have you done to fix it so far: rpm pick-up should be from back of alternator where red/brown wire connects. Reads an even 7.0 V at idle and 2000rpm when grounded at alternator body.
 

·
Registered
Joined
·
533 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #7
Thanks - no luck yet...

I found someone saying that the brown/yellow wire that I thought was the tach is instead the dash lights, and the white/slate wire with the funky clip is in fact the tach.

I measured 14.5 V at idle at the white/slade spade connector going into the back of the alternator - that would be a problem if that were the tach signal. Can anyone confirm if the white/slade wire is the tach? And what's the voltage coming out of the alternator into the white/slade? Does it go up and down in relation to rpm?
 

·
Registered
Joined
·
199 Posts
As far as I know the Tach is controlled by pulse rather than voltage. The voltage should be steady if read on a digital multimeter but an analog will show a quiver on the needle.

:pray:
 

·
Registered
Joined
·
8 Posts
Discussion Starter #10
Thanks - for future reference, what I found out is the brown/yellow wire connects to the 14.5V post on the alternator, and it is not the tach. The white/slate wire with the in-line connector goes on the 7V post on the alternator, and that's the one to work the tach.

I'm assuming I have stock colour wiring.

On my alternator, which is a DENSO (UK) model, the white/slate wire (tach) goes up top, and the brown/yellow goes down low.

That was the problem, and now the wires are on the right posts, the rpm gauge has come back to life and the red battery light is off.
 
1 - 10 of 10 Posts
Top