High volt problem... (1 Viewer)

[runthejoules]

Strange problem developed yesterday... at idle everything is fine, but as soon as the engine revs the voltage meter pegs high and shortly thereafter the abs light comes on followed by the airbag light. Come to a stop and the voltage goes back to normal and the lights go away. Engine runs fine and there isn't any other electrical issues. It's a new battery and the connections seem fine. I'm thinking ground from the alternator? Anyone experience something like this?

Thanks

 

[Irish Reiver]

Have you actually measured the voltage at the battery with the engine running?

 

[runthejoules]

Have you actually measured the voltage at the battery with the engine running?

Only at idle and when off and it's around 13

 

[Irish Reiver]

I think you need to break out the voltmeter and measure it at ~2000 rpm.

 

[jonheld]

I'm thinking ground from the alternator?

The alternator is grounded to the engine block through the case and mounting.
As mentioned, measure voltage across the battery terminals. Max voltage should be around 14.4 VDC. If you're reading much above that, then I would look at the voltage regulator in the alternator.
Is this an OEM Denso alternator?

 

[runthejoules]

yes oem alternator... it appears that voltage does indeed spike when the motor revs... around 17V

 

[jonheld]

yes oem alternator... it appears that voltage does indeed spike when the motor revs... around 17V

How and where are you measuring voltage?
I'm not sure what you mean by, "it appears that voltage does indeed spike when the motor revs".
This is not an interpretive issue. It is either correct or incorrect when measured with a proper voltmeter across the battery terminals. The purpose of the voltage regulator is to regulate voltage to a max of 14.4 VDC on the output of the alternator to avoid damage to the rest of the electrical system components.

 

[runthejoules]

at idle it's about 13V and as it revs up it goes to 17-17.5 just like to dash gauge is indicating. But now overnight the battery has been completely drained (it's new)... not even so much as a dome light will come on.

 

[SmokingRocks]

1st of all; Replace the alternator with a denso unit (you can get reman'd units from napa), sounds like your voltage regulator is ***d

2ndly how long have you been running it this way? you may have killed the battery with the excessive overvolt charging condition.

 

[runthejoules]

I drove it home from work... so 5 miles. Fortunately the batt is still under warranty!

 

[SmokingRocks]

should be fine if it wasn't for long. take it out, charge it up and see what happens. You need to take the battery out to replace the alternator anyway.

 

[runthejoules]

do you think I should try to replace the voltage regulator first and see how it goes? I was thinking the alternator was working since it was generating power...

 

[bajaphile]

Do you have a 60 series (shown in your avatar)? If you have external regulator, then I would definitely replace that.

 

[runthejoules]

Do you have a 60 series (shown in your avatar)? If you have external regulator, then I would definitely replace that.

I do have a 60, but this problem is on a 97 80 series... it's just not a photogenic

 

[ScottyRt66]

@runthejoules
howd this work out? This sounds EXACTLY like what’s happening with my 95 LC. Just started tonight.
Did you have to swap out the alternator?

 

[Kernal]

The voltage regulator on a FZJ80 is located under the rear cover of the alternator and can be replaced however the price for a replacement Toyota voltage regulator is close to the same cost for a complete reman'd Denso alternator. There are made in kerapp chynna voltage regulators that are cheaper but not recommended. As mentioned above, easier to get a new reman'd Denso replacement. Rock Auto also sells the Denso replacement.

 

[runthejoules]

@runthejoules
howd this work out? This sounds EXACTLY like what’s happening with my 95 LC. Just started tonight.
Did you have to swap out the alternator?

yes I just swapped the alternator and everything is good now... except I’ve got to figure out how to clear the airbag code

 

[Kernal]

Its been discussed. Search for Airbag SRS light turn off (or similar words).