UPDATED: REVILLA 1, RAC 0 SLR – red (alternator/charging light) staying on

[Nick Bassett]

Still having issues with my SL R… have fitted a new alternator & battery but when started, the red dash light stays on...

 

I do have a wiring diagram but don’t have a multimeter (JK!!), but to be honest electrics scare me a little!

A friend popped round yesterday with his multimeter and confirmed battery is good but it doesn’t seem to be charging the battery. My plan is to check various earth points on the car – the battery to starter is fine and I’ve stripped and cleaned the block to engine mount earth – it seemed pretty good anyway. There is one under the dash I need to check, plus one at the rear of the car I believe – any others?

 

If the problem still exists after all earths have been checked, I’m not sure what else needs to be looks at – any ideas?

 

Thanks

Nick

 

[Jonathan Kay]

What type of alternator and what are its current connections?

Jonathan

[revilla]

What kind of light do you have on the dash? Is it a proper old-fashioned bulb or a little LED? I've seen a couple of cases where the LED doesn't feed enough current (it only feeds about 4ma) to start the alternator in the way that a bulb would (maybe 100-150mA). The alternators were designed to be kick-started with a much higher current than the Caterham LED gives them. If this is the problem, you can wire a 2-4W bulb or about a 100-150ohm resistor in parallel with the LED.

 

Do you want me to bring multimeter / current clamp etc. to do a quick check when I come down on Thursday? What kind of alternator do you have?

 

Andrew

[revilla]

@Jonathan - "Current Connections"... You just can't help yourself, can you

[Nick Bassett]

It's a Magneti Marelli alternator - like for like replacement from an autofactors.

@Andrew - it's a standard bulb I think - I've only had the car 3 months, so still new to me.

If you could bring one along, I'd really appreciate it - thanks. 

[revilla]

Will do.

[Nick Bassett]

Thanks 

[TomB]

You should be able to tell with a multimeter whether the current from the alternator is charging the battery when the engine is running.  Find a Rover manual to tell you the voltages to look for - but essentially and as I understand it, the battery is 12v - it need to be charged at >12v to keep it topped up while running.  Any less, causes the red light to come on as it is not being topped up. 

If the multimeter shows <12v during running (not at idle), its probably the rectifier/ diode pack on the alternator has given up.  Wip it off and take it to an auto electrician who can replace the rectifier pack, or sell you a reconditioned one.   Ive had to do this a couple of times over the years, not great drama and not too expensive - certainly less than a new alternator from Caterham! 

 

[Nick Bassett]

Thanks Tom - it is a brand new, quality alternator, so should be working 100%...

Unfortunately it's not an easy task to wip it off... to get the top bolt out, I have to remove the primaries and with a Powerspeed exhaust that means removing the whole system... 

So hopefully, it is something simple like a dodgy earth connection...

[TomB]

Should 

I forgot about the rear mounting for the alternator - so yes, its not quite 'wip'. 

 On my 1996 K series, the engine bay earths are on the RHS engine mount-block (little black strap), lights earth near the RHS brake union, plus some that go directly to the battery negative terminal.  The cabin earth is near the wiper motor, and the rear earths use the the rear wing fasteners, securing a ring terminal to the inside skin.  A signficant proportion of electrical gremlins seem to be down to bad earths,fingers crossed that's it. 

[Nick Bassett]

No worries Tom.

Stupid question - but the earth near the RHS brake union - where exactly would I find that?

Thanks

[TomB]

On mine, there is an earth for the front lighting wiring attached to the chassis, near the 3 way brake union that splits the single copper pipe from the brake master cylinder to the right and left front brakes.   You should see a few black cables meeting together on a ring terminal or similar.  

[Wrightpayne]

The only earth cable affecting alternator charging is the one between the bellhousing bolt and the battery.

Ian

[TomB]

I forgot about that one! 

[Jonathan Kay]

Checking earth connections is a generally good thing, and Caterham suggests that bad earths cause ? 80% of smoke problems. But...

Problems with the warning light seem surprisingly common, and most of those discussed here don't seem to have simple solutions at the end of the story. I think that's because victims either replace everything in sight or end up living with the problem.

I'd approach it by investigating three specific types of cause:

1. Problems in the warning light circuit: LEDs (as above), wiring, wrong terminal on the alternator. (And it is a strange circuit... who thought this up?)
2. The alternator isn't charging properly.
3. The voltage on the warning light terminal of the alternator isn't being asserted properly.

Those are each quite easy to test. How about buying a multimeter (+ extra leads with croc clips) before Andrew's visit and asking him to show you how with the one you're going to end up with?

Jonathan

 

[Nick Bassett]

Thanks Jonathan.

I did read that approx 80% of electrical issues are 'earthing' related, so hopefully it'll be something straightforward.

It could be 1 or 3, but shouldn't be 2 as it's a brand new good quality alternator...

[Nick Bassett]

Massive thumbs up and thanks to Andrew Revill (Revilla) for fixing my 7 last night and highlighting the massive balls up made by the RAC... what was the issue I hear you cry? Well the RAC had wrongly identified the unconnected alternator live feed as an earth and connected it to the Emerald bracket! Why the cable was unconnected in the first place I don't know, but it would seem I changed the alternator unnecessarily! So, you live and learn...

On top of this, whilst working in actual sub-zero temperatures, Andrew then proceeeded to tidy up some of my wiring!

Andrew - thank you so much again - you are a star and a perfect example of the calibre of members in the L7C 

[Jonathan Kay]

Glad you're fixed. Well done, Andrew.

... but it would seem I changed the alternator unnecessarily!

You're nowhere near the first. But what was the sequence of events involving the RAC?

What type of alternator and what are its current connections?

Resistance is futile.

Jonathan

[Nick Bassett]

The red light is extinguished now JK. 

I called out the RAC just before Christmas when I had starting problems and it was at that point the stray cable was spotted under some other cabling.

The brand new alternator is a like for like replacement - Magneti Marelli. Connections haven't changed from what was fitted before.

[Piers300]

The start of a spares kit !!!

[Paul Mason]

Revilla is clearly a top man! "Andrew then proceeded to tidy up some of my wiring" .......... All I need now Nick is his address and preferred tipple as I have various crows nests under the dash and bonnet that I have literally zero clue how to even start sorting!! I am absolutely positively when Andrew area them he will take pity on me!

[revilla]

I'm just glad we got it sorted. Definitely the kind of thing you wouldn't guess unless you were stood in front of the car! Nice to meet you anyway Nick... no doubt our paths will cross again in the future. @Paul - Nick doesn't know where I live. I was "on tour". Bodged it and scarpered. But if you really want a hand... drop me a BM

[SM25T]

Well done Andrew.

[Paul Mason]

Thanks Andrew, whilst I do have a bit of a mess in terms of wiring, I am also North of the Wall so to speak in the frozen northerlands near Middlesbrough so not exactly local. I'll get it sorted at some point.......I'll just have to unplug 1 wire at a time, re-route and re-plug in until all tidy and ship shape. Good news is, all the electric's work even if they are messy.

[revilla]

Sounds sensible. Try to tie them into neat bundles that follow similar routes. Nick had some extra wires off the battery for immobiliser and 12V socket with decidedly dodgy ring terminals that looked like they were ready to drop off. Couldn't leave them like that when I had my crimpers and decent terminals in the boot so we just cut them off and did them nicely with a bit of insulated heat shrink over the top to keep them neat and supported. I didn't exactly rewire his car!