alternator blues

lotus · 10 Sep 2003, 16:45 (Ref:714275)

alternator
I am having some trouble with my race car alternator they only last one or two races the red light starts to glow i have traced the two main wires back and they have been joined together and run to the main cut off switch I know one should go to the battery and one to the ignition switch this is my first year with the car and it was well prept is this the way most race cars are wired??? can any one help

graham bahr · 10 Sep 2003, 20:40 (Ref:714501)

it sounds like its wired wrong, race cars with an alternator should have a cut out switch which has a secondary switch on its back, the purpose of this second switch is to feed the alternators output safely to earth via a resistor when the power is turned off with the engine running, if its not wired correctly when you shut the power off the alternator fries its diodes as it thinks the battery is dead flat and so puts out its maxium charge, but as the battery is disconected the current has nowhere to go so the thing gets fried

**Tim Falce** · 10 Sep 2003, 20:49 (Ref:714507)

Some alternators (Lucas type, forgotten the model No.)are wired with two wires that go to the battery and one to the ignition light. As Graham says it could be a faulty or incorectly wired cut out switch. I would find out what type of alternator you have before altering the wiring

graham bahr · 11 Sep 2003, 18:49 (Ref:715453)

i think ACR is the type your looking for falcemob

**Tim Falce** · 11 Sep 2003, 18:52 (Ref:715456)

yup!

graham bahr · 11 Sep 2003, 19:11 (Ref:715485)

years ago i suffered numerous alternator failures until i fitted a bigger pulley on it to slow it down.
i dont know about modern fitments but older alternators used to be geared for twice engine speed, with a maxium stator speed of 14,000 rpm, by reving to 8,000+ we were way over reving (16,000+) it and the stators were breaking up/exploding

my bmw has the other solution, no alternator, i just change batteries after practise

lotus · 11 Sep 2003, 19:57 (Ref:715545)

thanks lads the alternator on the car when I purchased it was a bosch but it fell apart I sent it for repair and they sent me a refurbed lucas that lasted one practice one race before the light refused to go out got a replacement plus a spare one both have done the same. I do run a large pulley the two main wires are joined and go to the starter and then to the main switch the main switch then supples the ignition plus the other lights +

Griff · 15 Sep 2003, 21:56 (Ref:720092)

LOTUS
You don't say where your alternator is fitted but a lot of
race car alternators fail due to overheating especialy
mid engine instalations. If you can run a supply of cold
air to the regulator / rectifier [rear] part of the alternator.
hope this helps
GRIFF

lotus · 16 Sep 2003, 20:32 (Ref:721153)

thanks, can anyone tell me which way the blades on the fan point ,is there a right hand or left hand depending on which side of the engine the alternator is on the fan on my one seems to be pointing away from the air flow ie blades pointing the same way as the alternator turns

graham bahr · 18 Sep 2003, 06:10 (Ref:722678)

the alternator rotates in the same direction regardless of which side of the engine its fitted, unless its on a honda engine or fitted in front of the engine facing backwards.

its always struck me that alternator fan blades look like they are facing the wrong direction, but in a normal fittment as you look at the they slope anticlockwise away from the direction of rotation, as the air is sucked in the rear of the alternator and blown out the front. if you look at a lot of bmws you will find a cold air feed to the rear of the alternator.

lotus · 18 Sep 2003, 21:39 (Ref:723530)

cheers fot that graham the exhaust is right behind the alternator so I will have a look at getting some cool air to it thanks again.

JimW · 24 Sep 2003, 10:04 (Ref:728537)

Quote:

Originally posted by lotus
. . . the two main wires are joined and go to the starter and then to the main switch, the main switch then supples the ignition plus the other lights +

At a bit of a tangent to your query lotus, but it sounds to me as if your setup is not legal (under MSA rules) or as safe as it should be.

The purpose of the cut-out switch is to isolate the battery for safety reasons. And that means that the cut-out must be, electrically speaking, next to the battery so that all other bits of the system are isolated. The starter should not be between the battery and the switch.

To improve the safety of the arrangement, the cut-out should be physically close to the battery as well.

But then I'm sure the scrutineer will have picked up your arrangement and told you to change it.

Regards

Jim

**Tim Falce** · 24 Sep 2003, 12:38 (Ref:728672)

JimW
I think the wiring would be something like: Battery to main switch then switch to starter and alternator on one feed and then the lights and ignition on another. I think Lotus has worded it a bit arse about face or the switch is wired wrongly, difficult to tell without looking

JimW · 24 Sep 2003, 13:05 (Ref:728705)

Hi falcemob

I entirely agree with you; that's how it should be. But I have seen so many cars wired wrongly that I feel it is sometimes helpful to get a check done.

I reckon that nearly 10% of the cars which I have cause/opportunity to examine critically after a significant shunt are defective in this area.

('Significant' means where I as Rescue Crew get involved, which usually implies actual or potential injury to the driver).

Regards

Jim

lotus · 24 Sep 2003, 16:19 (Ref:728845)

Hope this clears things a little ,the wireing is just as falcemob says(much better described )the main switch is between windshield and bonnet in front of driver. I have taken all the alternators back to the autoelec shop and they say all the alternators have different faults nothing to do with the car!!!! all were Lucas rebuilt units and he was happy to give me two more that are a later mod.AHHHH renewed plug most wireing nights in garage AHHH scream

Chris Griffin · 7 Oct 2003, 18:49 (Ref:743281)

Lotus...

Lucas = Prince of Darkness! Try and find another Bosch unit. They are better quality. Better bearings etc. I went through Lucas units every couple of races a few years back. The key is to get the wiring correct, slow it down and go Bosch!

zefarelly · 8 Oct 2003, 09:38 (Ref:743832)

The Ford uses Lucus and they fall apart . . . .I picked up a brand new nippon denso alternator on Sunday for £20 at the car show - jumble at Ricardo . . . . just need to fabricate a bracket and work out how to wire it up !

a dynamo pulley on an alternator works to an extant, drops the revs by about 25% . . .cheap and chearful, and effective

tangoed sparky · 28 Nov 2003, 22:16 (Ref:797551)

The lucas ACR alternator has a three pin plug no the back with two large terminals and one smaller terminal. The two large terminals should be battery + via your cut off switch. The smaller terminal should be connected to a warning lamp that is supplied by the ignition switch. In theory the alternator gives the warning lamp an earth. this is to excite the rotor inside the alternator when the alternator starts to turn it the turns this terminal to a positive thus casueing the lamp to go out. Also the lucas ACR alternator was improved in the 80s and became the lucas A127 this was fitted to all sorts of Ford and leyland cars and is more powerfull than the ACR but usually is the same fitment. Alot of Japaneese cars have externally regulated alternators and this makes them more complicated but as is always the case the Japs tend to make good qualitiy stuff. Hope this was of some help and cause any confusion.

**Tim Falce** · 29 Nov 2003, 10:04 (Ref:798069)

sparky
I have an ACR fitted to my car and the warning light doesnt go out when I start the car until I rev the engine to about 3000. After that it stays out when the revs drop to a tckover. Why does it not initialy charge until I rev the engine?

graham bahr · 30 Nov 2003, 09:18 (Ref:798967)

Are you running Std size pulleys or have you slowed the alternator down falcemob? it always used to be normal to need to blip the throttle to excite an ACR but 3000 rpm sound a bit exessive, still if it works.......

**Tim Falce** · 30 Nov 2003, 10:29 (Ref:799054)

the pulley on the alternator is standard, but it is on a Jaguar engine now, not a Ford (which it came off) so I am not sure about the difference in size of the crank pulley. But if it is normal to have to blip the throttle then thats OK as it works OK once it starts charging.

tangoed sparky · 1 Dec 2003, 21:48 (Ref:800719)

falcemob grahams right it sounds like your pully is the wrong size. It should put the warning lamp out at about 1000rpm. like you say the jag pulley is probley causing the problem but I think that you can get smaller pulleys from lucas dealers or good auto electrical out lets. It might be worth checking the wattage of the warning lamp bulb if its to high then that can cause the warning light to require a higher rpm to put the bulb out (bulb should be about 2 watt) also some cars dont have a bulb but they have a led and a resistor to due the same job.

**Tim Falce** · 2 Dec 2003, 15:14 (Ref:801552)

I can put a smaller pulley on the crank, what sort of revs will the alternator safely go up to?

graham bahr · 3 Dec 2003, 08:45 (Ref:802332)

14,000 is about your limit on an acr

graham bahr · 3 Dec 2003, 08:46 (Ref:802334)

14,000 is about your limit on an acr, although to speed it up you'd need a larger crank pulley not a smaller one

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