Electrical woes

Wiring, instruments, switchgear etc

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Electrical woes

Postby Phil Bradley on Mon Oct 05, 2009 10:13 am

Hi All

As I am nearing completion, I’m coming up with some electrical issues, the latest being the starter motor burning out. This, it appears, is why we couldn’t get the car started at the dyno towards the end of the day. It’s a real pain in the posterior as I wanted to get the wheel alignment done on Saturday.

This weekend I got stuck in the wiring and have (unfortunately) moved the battery back to the front. I wired the negative terminal to the engine near-side and from engine far-side to the chassis. I have taken all the negative terminals from the dash (ECU, FIA switch, gauges and buttons) with their own wire directly to the negative terminal on the battery. The alternator is now connected directly to the battery positive and then the battery positive is connected to the FIA switch. The other side of the FIA switch is connected to the starter motor and to the main positive power for the loom.

The FIA switch is the one with 4 additional points on it which I have wired according to the diagram. As it is now, the terminal direct from the battery was getting extremely hot – I presume now that this is because of the starter motor which was getting so hot that it smoked and was too hot to touch.

I stripped the starter motor yesterday and it was full of “dust” which turned out to be copper dust. The spindle on the motor was binding on the rear bearing which was causing the motor to not spin properly, making the same sound as if the battery was dead. One of the things I checked was to hook up a new battery and same thing happened.

So, now I need to get another starter motor and hope (fingers and toes crossed) that the wiring wasn’t/isn’t at fault.

Cheers,
Phil
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Re: Electrical woes

Postby andredp on Mon Oct 05, 2009 10:50 am

Phil

You cannot run the main starter wire (thich high current feed) through the FIA cutoff switch, it will burn that switch. Run the thich cable directly to the battery. The solenoid cable coming from the start button/ign switch should take it's feed from the FIA switch (switched side) preventing starter activation when the FIA switch is switched off.
Andre'
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Re: Electrical woes

Postby muller on Mon Oct 05, 2009 12:51 pm

+1 for what Andre said, just connect the starter power cable to the the alternator charging cable, no need to run a 2nd power cable to the back of the car.
Anton

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Re: Electrical woes

Postby Phil Bradley on Mon Oct 05, 2009 3:31 pm

Hi Andre, Anton

I originally had it like that.
But, for some reason I am just not grasping the concept. I've even drawn it out on paper to get a logical view of it...
So, battery positive alternator, starter and FIA? Other side of FIA to main power for controls etc.?

I went to an auto electrician on saturday and he mentioned something about a connector that you can tap into a c cable with so that there is a single cable and not multiple break points. This was for the earth wire though. What is the best way to wire it as the welding cable is thick and cumbersome to get more than one wire on a single connection point.

Thanks,
Phil
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Re: Electrical woes

Postby andredp on Mon Oct 05, 2009 3:59 pm

I don't use a multiple connector FIA switch, so I can't help with the bottom 4 connectors, but the rest is fine, apart from the red running from the starter to "ignition coil". That must not run to "ignition coil", but rather to "main electrical feed"/Outputs via your start button/ignition switch.
Andre'
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Re: Electrical woes

Postby muller on Mon Oct 05, 2009 4:16 pm

Hopefully this makes more sense. If you want you can ignore the four other connectors on the FIA switch, you do not need them.

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Anton

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Re: Electrical woes

Postby ross on Mon Oct 05, 2009 5:20 pm

Hi Phil,
What I did was run the heavy cable to the starter, from there I picked up a connection for the main power input to the cut off switch (FIA), this cable is only 6 square mm so it's a lot lighter and easier to work with than the welding cable. You only need the heavy cable as far the starter to accomodate the crancking current. I also ran a 6mm cable from the starter to the alternator. Effectively I'm using the main contact on the starter as the main power supply. Hope you come right.
All the best,
Ross
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Re: Electrical woes

Postby Phil Bradley on Mon Oct 05, 2009 6:30 pm

Thanks guys
I'll have a look at it tonight. I don't know why I am hitting a blank with this thing...
I'm collecting the new starter motor tomorrow. Any ideas how the other one could have burnt out going with the way I have described how it was previously disconected?

Cheers,
Phil
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Re: Electrical woes

Postby andredp on Mon Oct 05, 2009 8:42 pm

fiaswitch.jpg
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Ok, here goes:

1 x Bigass wire from batt + to starter big terminal (big red in pic)
1 x Fairly big wire from batt + to alternator big terminal (big green in pic) or if easier, leave green out and connect alternator big terminal to starter big terminal (blue in pic)
Wire in purple from main elec feed via start button to small terminal on starter, and if you want from ignition switch starter terminal to starter small terminal.

Ross, what you did is strictly speaking not the best to do. Taking the power for the rest of the car from the big lead on the starter, will cuase a power drop to the rest of the car when the starter is drawing power. It *may* work, but might cause some problems in future. I know you did it because you have the long cable running from the back from batt + to your starter, but like I said it is not ideal.
Andre'
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Re: Electrical woes

Postby ross on Mon Oct 05, 2009 9:03 pm

Hmm Andre' you may have a point, easy enough to check, measure the voltage at the battery terminals and at the starter terminal under cranking, see if there's a difference. In any case, no matter how you connect it, the battery will pull down under cranking, it could be worse in my case due to the potential for a volt drop along the cable from the battery to the starter due to the length. I'll worry about it when it presents as a problem, if necessary I'll run another cable from the battery. Thanks for the heads up.
Cheers,
ross
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Re: Electrical woes

Postby andredp on Mon Oct 05, 2009 9:25 pm

We can test it soon enough ;) Yes, voltage drop on the cable is the worry. For interrest, we struggled starting a Locost this weekend because the voltage drop on a set of big jumper cables was too much. Bolted in a fully charged battery and problem was gone.
Andre'
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Re: Electrical woes

Postby Phil Bradley on Tue Oct 06, 2009 7:39 am

Thanks Andre

You should know by now that I'm one that needs pictures :-)

The “bigass” wire will be the welding cable. Will 6mm (as Ross has used) be suitable for the rest? If not, what do you recommend?

The issue I was having in my previous setup was that the voltage was dropping down to 4v and the Microtech needs a minimum of 8.8v for start up. I am assuming that it was the starter motor that was draining most of the power.
Another question, when I measured resistance across the battery with FIA off, it read +/- 500 ohms, when FIA switch on it read 0. Is that correct or do you reckon I have a power leak somewhere?

Ross, if I were you, I would get it sorted by the (Andre’s) book now. There is nothing as frustrating as getting the car going, thinking everything is fine only to have a latent electrical issue surface at a later stage. Whilst Andre’s at your house, use him… :-)

Cheers,
Phil
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Re: Electrical woes

Postby andredp on Tue Oct 06, 2009 8:48 am

Hi Phil

Yes the faulty starter may have been the cause of your drop to 4V, but you will only be able to confirm once you have replaced it. Measure the voltage on the ECU while cranking and make sure that it is at least 10V while cranking. 6mm wire is suitable for the rest yes.

You cannot really measure the resistance across an open battery, since it differs depending on battery state. With the FIA switch on, measuring 0 resistance is a bit concerning, but yeah the resistance should be very low when switched on. Make sure you don't have a dead short somewhere, but I guess it is fine since you have had the car running already.
Andre'
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Re: Electrical woes

Postby ross on Tue Oct 06, 2009 9:52 am

Hi Phil you read my mind, I'll make sure I have a piece of 6mm cable availble just in case. I need to get a few things sorted before saturday to get ready to fire up the engine, but if I get achance I'll run the cable anyway.
Cheers and good luck,
Ross
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Re: Electrical woes

Postby Phil Bradley on Thu Oct 08, 2009 11:45 am

Sorted - Thanks guys for the input.
I installed the new starter motor last night and had her iddling at 22:00 last night :-) Sorry neighbors...
Phil
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