ms85er

Electrical circuit issues

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I'll try and get a reading with the DMM when I can get someone to help me, can't drive and get readings myself.

Edited by ms85er

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So update,

I have tested everything imaginable. I get 14.2 volts at the battery at idle, however its not consistent. As soon as the idle drops the voltage goes all over the place down to 11 volts or even lower. Installed a brand new battery today. No difference. The Fuel pump was certainly not getting enough power, the ignition system is barely getting enough power at low rpm, car randomly stalls. I have put a voltage regulator on the fuel pump and it works brilliantly now, I can hear it loud and consistent now. So I was using the alternator that came with the motor when I had these issues. I installed an denso reconditioned 100 amp alternator with appropriate pulley. The pulley ratio is still very close to the original pulley that came on the alternator so that's got nothing to do with it. The only difference is since the first aged 70amp alternator and the 100 amp I now get a dim alternator light on the dash, where as the 70 amp alternator was happy. I have run a wire directly from the post on the alternator to the positive on the battery with nothing else hooked up, makes no difference. I've installed extra grounding wires and check the voltage at the post of the alternator to the battery ground and there is the same 14.2 volts at idle. The sense wire going to the alternator reads about 14.1 volts but I don't see there being any issues there as the alternator just needs to know roughly what voltage the battery is at.

 

Anyone here an auto electrician, I give up.

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ITS FIXED!!!!!!!!!!!!!!!!

 

So I have no idea what those erratic multi-meter readings were all about, maybe my multi meter is stuffed, Also, I purchased a reconditioned 100amp alternator which was fitted to the car when I was having these issues and it was faulty.

The problem was a combination between throttle cable and idle adjustment, although the particular motor I have doesn't technically have an idle adjustment, it's an "idle bandwidth" type adjustment for the ecu, its primarily used to adjust the idle. So overall it was a massive headache. 

Thanks for the help everyone!

Edited by ms85er

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Sweet as, but hang on, just so I understand.

The symptoms were describes as a varying voltage which was making the lights go dim and bright right?

Was the problem the faulty alternator, or the idle cable thing??

 

For the record, I find in ever car I've ever tested volts go down as u rev the engine. And I've aleays just accepted that's because the electrical system is being taxed by the coil working harder?? More sparks???

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14 hours ago, rebuilder86 said:

Sweet as, but hang on, just so I understand.

The symptoms were describes as a varying voltage which was making the lights go dim and bright right?

Was the problem the faulty alternator, or the idle cable thing??

 

For the record, I find in ever car I've ever tested volts go down as u rev the engine. And I've aleays just accepted that's because the electrical system is being taxed by the coil working harder?? More sparks???


Yah my post probably seems confusing because the whole thing was confusing. It was at the point where I was trying anything to get it to work. Those multi-meter readings were wack.

An interesting thing I learnt was that the alternator really does push out most of the voltage to operate the vehicle. If for some reason your not making close the 13.8 or 14.2 area

at idle your 12v battery doesn't do a whole lot. It will keep the car running but they are optimised for starting the car primarily.

 

My problem was varying voltage making lights go dim and fuel pump struggle. I had this issue with the first alternator and the second reconditioned denso alternator (thats right a faulty reconditioned denso). The denso alternator also threw the charge light but my old alternator didn't. I didn't think adjusting the idle and throttle cable was really necessary as the car idled fine. However, while it did idle in line with typical idle for that engine, its recovery from an idle drop was just too slow. This is where that idle adjustment thing also helped, so the 14.2 volts would go down below 11 volts. As I learned the battery is really only for starting the car, it just can't handle the demands of fuel pump and lights that well. It's funny because only 1 website out of 12 I visited actually explained that correctly. Every website that thoroughly explained charging systems basically gave the impression that if the alternator isn't working it just won't charge the battery.

 

Edited by ms85er

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Yep that's what I find most frustrating about research in the net. It's so common for a very authorative looking source to be completely wrong, or simply miss the most important facts.

Truely knowledgeable people don't tend to publish their knowledge on the net, and I suspect this is because it's boring to them, it's their job. However, enthusiast, hobbyists, and website advertising hungry original content providers will just do anything to make a website with click-bait style information.

You've really got to find a good forum where people who specialise in an area hang out and talk. I don't think there is such a forum for automotive electrical though.

I have a mate who is an electronics engineer, hes semi autistic and is on a first name basis with the electrons in a circuit. I'm lucky I have him available at request. He will find an absolutely false concept or explanation in any written online electronics information source. Apparently it's a very intricate and 4 dimensional subject which requires playing around and practice followed by theory and not the other way around. So I don't trust anything except my own interpretation of an electrical diagram nowadays.

U can be guided by online I formation I guess, but it's mostly incomplete, and incomplete information leads to misunderstanding.

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Too right. Experience helps a lot as well. Your electronics engineer mate sounds like a handy consultant.

Edited by ms85er

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