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Post by Baldrick on Jun 8, 2012 18:10:21 GMT
Have a charging problem. 14.6v at the alternator, but not getting to the battery. The ammeter dances around and occasionally shows a + charge but genally stays in the - with a load. I have a modern alternator so the relays and field wiring are obsolete.
I am suspecting a dodgy wire/connection in the charging circuit. The wiring diagram shows the charging wire going via the ammeter shunt and the starter. Where is the shunt located physically in the car as I want to check the connections there as well as at the starter. As the car starter works fine and turns the engine fine, I further suspect the problem will be between the starter and the alternator.
Any comments or thoughts are welcome.
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Post by Phil Nottingham on Jun 8, 2012 18:30:33 GMT
Under the dash is a big junction strip which connects all the battery cables and the ammeter shunt. This is in direct line of a leaking screen seal. Just behind the steering column.
Also check the starter motor solenoid cables terminals and the loose cables which can corrode internally - this is primary supply point after the battery itself.
I would rewire anyway direct to alternator from there intially leaving existing cables in place and connected to see what happens then reinsate via said terminal strip to get ammeter working via new cables
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Post by stevew on Jun 8, 2012 19:05:03 GMT
Hi Baldrick, this what your looking for, above the parcel shelf above the steer column under the dash, difficult to get to.  They are very large spade connectors ( 1/2 inch)which I don't think are available now so be carefull.  |
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Post by Phil Nottingham on Jun 8, 2012 19:18:11 GMT
Shunt is mounted close by too - smaller version with its own loom to ammeter and not actually direct or essential part of circuit unlike 3 Litres
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Post by Baldrick on Jun 8, 2012 22:46:40 GMT
Thanks. I'll check tomorrow or Sunday when I escape the wife and kids!
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Post by Baldrick on Jun 9, 2012 9:57:55 GMT
I checked the voltage at the alternator with the engine off and it was .1v less than battery, whick I thought was ok. Bear in mind there is 2 + posts on the alternator - the one where the charging wire spade is connected and a post which is easier to access. I measured at the post.
Started the engine and checked v at alternator. 14.4v. Checked battery 12.3v. Checked shunt and it was 12.3v, so I determined the problem was on the charge wire from alt to shunt. Checked the spade connector on the charge wire at the alt and it arced! Removed it and it was heat damaged. Removed and crimped and soldered on a new ring terminal and started the engine. 14.4v. Woo hoo! Easy fix for once!
I had been staring at the problem all the time but because I was checking voltage at the second post, I never noticed the melted sheath on the spade.
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Post by Baldrick on Jun 9, 2012 11:27:24 GMT
Stevew,
Interestingly the indicator flash is better than it was, so maybe this connector has been deteriorating for some time and wasn't 100% during your ownership. Hopefully rev counter will be 100% when I get it back from Richfield, if I ever get it back - they are not the fastest.....
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Post by Steve P5b on Jun 11, 2015 19:01:38 GMT
I never read this post previously, but this car did have annoying fault with an erratic rev counter. This could well have been the problem all along.
Some thing for other owners with this problem to look out for maybe.
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Post by geoff53 on Jul 8, 2019 20:51:02 GMT
Hi all
Anyone encountered a wiring overheating problem behind ammeter on mk2 3 litre !
Mine created smoke from dash yesterday and behind the cowling there is a red wire loop between the ammeter poles with a 40amp blade fuse in between ? Is this correct ? On investigation the sleeving had begun to melt, I found the connection was loose, hoping this was the cure ? Stopped the smoking and taped up, the wires still proceeded to get hot including the fuse, which eventually blew and I lost ignition, new fuse and working again, but still getting hot !
Any ideas ?
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Post by enigmas on Jul 9, 2019 5:25:12 GMT
Ensure all the wired connections are clean and bright. Dirty connections cause heat buildup in the wiring due to the high resistances created. Also ensure that the connectors on each wire are not frayed and carrying current on a few strands.
Check that the voltage output from the generator(?) if still fitted is correct for your car and not too high. I'm guessing around 14.7v but check your WSM specs.
You may be running too many accessories all at once or some (halogen headlights) may be drawing too much current for the original wiring. Fit heavier gauge wiring to this circuit and relays where required so that switches don't carry the load.
If you've fitted an alternator (in place of the original generator) the existing wiring may not up to coping with the added current flow...similarly with the original AMP gauge. Pushing 40-60 amps through a 30 amp gauge generally destroys the gauge and will cook incorrectly sized wires and components.
The wire loop at the back of the gauge may be there to bypass some of the current. If so fit a correctly rated amp gauge and wires.
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Post by Phil Nottingham on Jul 9, 2019 5:27:31 GMT
The entire car electric current apart from the starter motor goes through the ammeter on 3 Litres - there should not be a fuse between the 2 terminals. Loose terminals will cause overheating. I would remove the fuse anyway as it it does blow all the electrics will stop. Remake the terminals as the ends of the cable may have broken.
Given the age of the wiring I would fit a battery cut-off switch in the passenger footwell bulkhead so it can be quickly reached
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