Alternator Overcharging

[Djaniero]

Bit of a weird one guys for the electricians in the house.

Basically I jump started my car a few months back, and connected the jump leads the wrong way around ...School boy error I know.

Anyway, it blew the 80amp fuse and I had no power whatsoever in the car. I bought a new fuse, fitted it and all was fine.
The car has been parked up for a few months since then, so I haven't really driven it until today.

My oem double din radio wasn't working so I took it round to my mates- who is an electrician - to have a look.

He traced the issue to be a bad earth. Then on closer inspection, he noticed that there was no earth on the radio, or the interior lights.

We then checked the fuse box in the bonnet, and my 80amp fuse had started to melt at some point :s

We also checked the battery with a voltmeter, and it was reading 15v @ idle, and went slight higher when the revs were increased, which my mate said was too high?

So just to summarise:

1. I have no earth on the radio, or interior lights - Light isnt working and radio only works when we use an alternate earth.
2. My 80amp alternator fuse has started to melt - still working.
3. I'm getting a 15v plus reading on idle.

Could this be an alternator issue i.e. is it over charging? Could I have damaged it in some way when I connected the jump leads up wrong.

Apologies for the long ass post. But I just wonna get my car back on the road asap.

Thanks

 

[garry goodall]

The overcharging could be due to a faulty alternator rectifier ?

As for the earths, do you mean the radio has an earth attached but it doesn't work until you use a earth cable attached to a different location, it's possible you burned an earth cable out, can you trace the cable and replace it with a new one ? Am not sure where the earth is on the interior light, it might be another trace it job

 

[dac69er]

When I connected a battery up the wrong way in the dark it blew the radio and dome fuses as well as the main fuse.

I would check all other fuses.

It is possible you melted an already poor earth wire.

As for the overcharging. That sounds like the rectifier in the alternator. Probably got damaged when you connected the jump leads incorrectly. Jap cars do tend to charge a little higher, but 15 volts is too much.

 

[Djaniero]

The overcharging could be due to a faulty alternator rectifier ?

As for the earths, do you mean the radio has an earth attached but it doesn't work until you use a earth cable attached to a different location, it's possible you burned an earth cable out, can you trace the cable and replace it with a new one ? Am not sure where the earth is on the interior light, it might be another trace it job

Ok, so I'll need to replace the alternator? Can it be any Toyota alternator or does it have to be specific for my car? Its a 94 GT?
Sorry, yes thats what I meant i.e. the radio has earth attached, but oly works when you attach it to a different location. Ok cool, I'll have a look and trace the earths.

When I connected a battery up the wrong way in the dark it blew the radio and dome fuses as well as the main fuse.

I would check all other fuses.

It is possible you melted an already poor earth wire.

As for the overcharging. That sounds like the rectifier in the alternator. Probably got damaged when you connected the jump leads incorrectly. Jap cars do tend to charge a little higher, but 15 volts is too much.

OK, so check the fuses under the dash and under the bonnet? My electrician said that we should replace the earth under the bonnet,( near the wiper washer bottle) as it was slightly corroded also.

So as above, I need to change the alternator? What volts should the charge usually be?

 

[dac69er]

Yup, double check them all to be sure.

You don't have to change the whole alternator. Just the regulator part inside it.

Normal charging is about 14v. What voltage does the battery sit at once charged?

And yes, replace any dodgy looking earth cables as they are likely to cause you issues!

 

[Djaniero]

Where can I buy a voltage regulator from?

Also how do i remove the alternator ? Never done one before.

Thanks again

 

[bongskag]

theres places that can do alternator reconditioning, they will replace the bit for you

 

[garry goodall]

Might be cheaper to get a good second hand unit,

To get it off there is an adjuster bolt to undo, you can then take the belt off, the. Undo the long bolt the alternator pivots on, couple if cables on the side and it's off, remember to disconnect the battery

 

[dac69er]

as above to remove.

search 'toyota voltage regulator' on ebay and match it up to yours. or just take it to an auto electrical place to get it reconditioned. that way you get a new regulator, new bearings and new brushes so it is as good as new.

 

[Djaniero]

Thanks for the info guys. I'll try and get it removed at some point this week. Am I right in thinking I will have to remove the alternator from underneath, so axle stands would come in handy?

I've managed to find a used alternator on uks forum. I'm just waiting for some better pics, so I can compare the plug/connector to my alternator.

If not, I'll get mine reconditioned. Either way I'll keep you guys posted.

 

[dac69er]

you are correct. underneath is the only way. its a bit fiddly, but its ok.

 

[Djaniero]

I bought an alternator, off a forum member on Monday, which was meant arrive yesterday - still not arrived today and I'm fucking :angry2: as I was meant to be heading away this afternoon to see family for the weekend, and now I have no car to do so.

Anyway, my cousin had a spare alternator in his Garage, from a corolla T Sport, which I thought may fit, but the alternators are different.

The voltage reg in my alternator has failed, so would the voltage reg from the T sport alternator fit my original alternator?

(Starlet Alternator is on the right, T sport alternator is on the left)


alternator2_zpsdd787bf0.jpg

T Sport Alternator

alternator_zps74d779a6.jpg

Thanks

 

[dac69er]

You may be able to make it work, but it wont be a direct swap. The plug connection would be wrong for a start, and i don't know what the fitting is like onto the alternator and commutator.

 

[Djaniero]

Thanks mate.

I scrapped the idea, and my replacement alternator arrived this afternoon.
However, after fitting it, my battery light stays on, and the square light with the heat lines going through it - not too sure what that one is :s. Also there is an intermittent high pitched noise, coming from the alternator.
Is the replacement alternator screwed dyou think, or maybe the belt isn't tight enough?

 

[Rev]

Take the belt between your thumb and first finger, rotate the belt 90 degs to the vertical if it resists firmly there at 90 degs and goes no further it is tight enough.

 

[Djaniero]

I'm going to double check it this evening. Would a slack belt cause me to have the above issue? I thought if it was slack it was be squealing like crazy?

 

[dac69er]

Sounds like the belt isn't tight enough. Bit could also be a knackered alternator.
did you charge the battery before fitting the alternator?
if the battery is flat or fucked then the alternator may struggle to keep up.

 

[Djaniero]

Belt was mega slack....my bad. Tightened it up again, but then it was squealing big time.

Loosened it slightly, but if still squeals a little until the car is warmed up. Battery and water light are no longer on after engine is fired up now though
No i didnt charge the battery...I bought it new recently. Should i have charged it before hand?

 

[dac69er]

It will put a big strain on the alternator if it is flat. That's probably why it squeaks so badly. Take it for a good drive and it should be ok.

 

[Djaniero]

Ok cool. Will take it for a good drive this evening. If its still squealing, should I try and adjust the belt again?