Lotus Elan

Alternator Problem

PostPost by: Maulden7 » Sat Mar 21, 2015 10:13 am

Brise alternator, only starts to charge when the engine revs are above 3000rpm? Above 3000rpm everything works fine.

Any thoughts?

Thanks.
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PostPost by: billwill » Sat Mar 21, 2015 10:50 am

Something wrong with its regulator or wrong wattage indicator light, wrong size pulley?

Alternator needa a smaller pulley than a dynamo so that it spins faster.


This has been discussed before on here.


See if your answer is in this topic:

lotus-electrical-f38/alternator-not-charging-t19525.html

or this one:
lotus-electrical-f38/new-alternator-not-charging-batt-light-stays-t28734.html#p190639
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PostPost by: Maulden7 » Sat Mar 21, 2015 1:09 pm

Thanks, checked all those before posting & no answers there.

Pulley is the right size, light goes out correctly. I chased the problem by fitting a temporary small digital voltmeter.

Not sure how I can check the regulator?

Alternator came from TTR (several years ago) & they are trying to help, but want me to send the unit back to them which I was hoping to avoid.

Thanks again.
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PostPost by: gus » Sat Mar 21, 2015 1:12 pm

How many wires go to the alternator? It acts as if it has no power connection, which could be the case for some alternators, or it could be a bad regulator. The regulators are usually a couple of screws if you know the donor car
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PostPost by: billwill » Sat Mar 21, 2015 9:30 pm

When you say the light goes out correctly do you mean at about 1000 RPM or at 3000 RPM?

If it is at lower RPM, that implies everthong id OK anyway; You won't see the voltage rise from 12 ish to 14 ish until the battery has 'reloaded' the charge used during the starting actions. So you may indeed not see much indication on a voltmeet untill abou 3000 RPM.

You really need to use an ammeter in circuit to test if an alternator is charging, checking the voltage is not the best indication.
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PostPost by: oldchieft » Sat Mar 21, 2015 11:25 pm

It would help to know what Brise unit we are discussing?

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PostPost by: Maulden7 » Sun Mar 22, 2015 10:30 am

Thanks guys, much appreciated.

The ignition light goes out at around 1000rpm, that's what is confusing me as well!

However, there is definitely something wrong. Twice now I have been competing in regularity rallies on rural public roads in France - so a whole day each time running at relatively slow speeds / rpm & with a lot of engine stopping / restarting - & both times the battery (a high capacity gel racing type) went so flat that the car simply stopped as there were not sufficient volts to fire the electronic ignition (fortunately ..... both times after the rally had finished & I was driving to the parking area - got pushed in - borrowed a battery charger - 1 hour later the car started & ran fine)

It was these experiences that led me to fitting the temporary digital voltmeter, & after starting up (the car starts very well - electric fuel pump!!) & when driving off the volts sit stuck around 12v permanently until I rev the engine above circa 3000rpm (which I don't do until the engine is up to normal operating temperature - say circa 70degF) then I see circa 14v which falls to around 12v after a few minutes. When I load the system - headlights / heater motor etc - everything looks fine with the engine running above 3000rpm.

Normal open road running & track stuff is obviously fine.

I will remove the alternator next week & post again.

Thanks again.
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PostPost by: billwill » Sun Mar 22, 2015 12:17 pm

Given your symptoms, it is probably best to get a new regulator and diode pack fitted in the alternator and have it bench tested.

Personally I would just get a reconditioned alternator.

A faint possibility is that the slip rings are dirty or the brushes worn out.
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PostPost by: Chancer » Sun Mar 22, 2015 3:41 pm

Something in the depths of my memory is telling me that its something to do with "self excitation" :oops: and the warning light circuit, I would have to go back through my automotive electrics textbooks but I seem to recall that without the warning light circuit or something or other the self excitation and charging would only take place above 3000 RPM.

Might be Worth a Google although "self excitation" might bring you rather a lot of other results :lol:
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PostPost by: oldchieft » Sun Mar 22, 2015 4:30 pm

Is it a two wire or three wire unit?

i.e. output and warning light or output, warning light and switched feed?

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PostPost by: billwill » Sun Mar 22, 2015 4:54 pm

oldchieft wrote:Is it a two wire or three wire unit?

i.e. output and warning light or output, warning light and switched feed?

Jon the Chief


Ah yes, you would get symptoms like you describe if it is a 4 wire unit and the link between F and IND is missing.

Image
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PostPost by: Maulden7 » Sun Mar 22, 2015 7:07 pm

Excellent help folks, I'll get that checked & come back.

Thanks.

Edit - interestingly, I did get a thought from Stuart at TTR that "there might be a wire broken at the back" ....... or missing??? I finished all the wiring mods in a new termination box (where the regulator used to be fixed) in the engine bay.

Edit 2 - should have added .... I'm working with an S2 here, so minimalist wiring.
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PostPost by: Maulden7 » Mon Mar 23, 2015 11:15 am

Alternator type is Brise 5021 ACR 3 wire regulator type - nothing obviously missing or wrong.
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PostPost by: oldchieft » Mon Mar 23, 2015 8:01 pm

I think this unit is a version of the Lucas A115i or A127i.

I found a web site that may be relevant.

http://www.qxcomponents.co.uk/tech.pdf

Quote.
Lucas A115i and A127i

A common complaint we encounter when either an A127i or an A115i alternator has been replaced is the warning light on the dash board staying on.

This is due to a mix up when connecting the wiring, the terminals are marked.
B+ Main battery feed.
D+ Warning light
W Phase terminal (12 volt output)

The mistake made is connecting the warning light to the W terminal not the D+ as it should be, this mistake causes the warning light to stay on.
Un-Quote.

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PostPost by: Maulden7 » Tue Mar 24, 2015 11:50 am

Thanks for the help fellas, & I've now cracked the problem. It was a "wire off" on the back of the alternator, but not obviously so!

This morning I went around all the car wiring with my multi meter checking for 12v, & everything seemed to be ok, albeit that I thought the ignition light was a bit dim in the instrument, but didn't take that to be of any significance. Then I started to pull the circuits apart, & with the ignition bulb holder out in my hand I noticed that the bulb was behaving a bit erratically with the ignition switched on, the light was fluctuating a little (which I hadn't noticed with it all in the normal place) So ...... I pulled the connector off the back of the alternator to check volts there, 12v aok on the red wire, & the ignition bulb was now noticeably brighter & not fluctuating with the circuit made through the multi meter! Ahhhh ...... the spade connection on the back of the alternator was not making proper contact with the connector on the red wire supply from the ignition switch

After some fiddling with the alternator connector, now the ignition light was bright & steady, start up the engine ...... bingo! Problem solved, it was the connection between the alternator connector & the alternator itself. Not exactly an obvious wire off, but the same thing electrically, the alternator was not self exciting until the engine rpm was driving it faster, & hence not charging a low revs

Ok, it's taken me nearly 4 hours to get there, but the simple solutions are always the best!!

Thanks again.
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