Have I done wrong? New alt with internal reg

[Arl37]

I was having problems with my old alt draining voltage so I bought a new internal reg alt. The exact one recomeended in in the Frequently asked qurestion section. Wired it precisely as Frequently asked questions said except I didnt hook the black ground wire at the alt to anything. Alternator works fine and gauge show it is charging. However, the drain as shown on multimeter is 12.5 volts when engine is shut off.? disconnet red wire to terminal on back of alt ,where it is supposed to go, and drain drops to .25 volts. it is .25 volts. Have I done something wrong? truck is 69 C10 307
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[Autoblueprint]

Originally Posted by Arl37

Have I done something wrong? truck is 69 C10 307

First of all...are you using this proceedure for checking for a battery drain?

To check for a battery drain:

(1) Key in off position.
(2) All accessories to off.
(3) Disconnect NEGATIVE battery cable.
(4) Place one lead of Multimeter on NEG battery post and the other on the disconnected NEG battery cable.
(5) Read voltage on meter

[Arl37]

Yes. I unplugged every plug dash colum, every fuse at least twice. at this time I'm more concerned about why the new alt is drawing 12.5 than any thing else
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[68gmsee]

12.5 vdc with everything turned off is good but check for battery drain like autoblue mentioned.

[Autoblueprint]

Originally Posted by Arl37

Yes. I unplugged every plug dash colum, every fuse at least twice. at this time I'm more concerned about why the new alt is drawing 12.5 than any thing else

Ok...if you used the proper proceedure to check for a drain...then...with battery cables on and IGN in ON position...do a voltage drop on the ALT wire itself...if it is more than .5 volt...replace the wire...use 8 gauge wire if you need to replace it.

[Autoblueprint]

Originally Posted by Arl37

Yes. I unplugged every plug dash colum, every fuse at least twice. at this time I'm more concerned about why the new alt is drawing 12.5 than any thing else

At the BAT terminal of the ALT you should be reading 12.5 volts and that is normal...HOWEVER...if you are reading 12.5 volts from the NEG battery post to the NEG battery cable...that is a massive drain that would kill the battery within a hour or so.

So to try and help you out here please tell us are you checking for a battery drain the way I described or not?

[Arl37]

Yes I am checking for drain as u described.at the Meg batt post. I under stand it is a massive drain
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[Andy4639]

Sounds like to me you are reading voltage on the back of the alternator like it should. Red wire to alternator is a direct link to battery +.

Arl37,
disconnet red wire to terminal on back of alt ,where it is supposed to go, and drain drops to .25 volts.

[Autoblueprint]

Originally Posted by Arl37

Yes I am checking for drain as u described.at the Meg batt post. I under stand it is a massive drain

Ok...now...do the voltage drop test on the ALT wire and see what you are reading.

[Autoblueprint]

Originally Posted by Arl37

Yes I am checking for drain as u described.at the Meg batt post. I under stand it is a massive drain

Opps!! Stupid me! I said Volts when I meant mili-amps when checking for drain:

[Arl37]

Sadly I have a pos multimeter frm Harbor freight an tool. Dosent have amp meter. Going to get one in the am. Between now and then any thoughts on why such a big drain at bat from a new alt. Thanks for ur help
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[Autoblueprint]

Originally Posted by Arl37

Sadly I have a pos multimeter frm Harbor freight an tool. Dosent have amp meter. Going to get one in the am. Between now and then any thoughts on why such a big drain at bat from a new alt. Thanks for ur help

Unfortunately...we need to know what the mili-amp reading is to have a proper diagnostic of the parasitic drain...which means...you will have to do the drain test again using amps on the multi-meter...and if you read more than .050 mili-amps...then you will have to pull the fuses one by one again.

However...you can do the voltage drop test on the ALT wire with the meter you have now...and if you find it has more than a .5 Volt drop...that would be the problem...then replace the ALT wire.

[CG]

This is a good thread. If there isnt already one like this over in FAQ this should go there. Nicely done guys, way to help out in an easy to understand way.


Mark

[Autoblueprint]

Originally Posted by Arl37

I was having problems with my old alt draining voltage so I bought a new internal reg alt. The exact one recomeended in in the Frequently asked qurestion section.

Can you post the FAQ link that you followed?

Also...did your old system have an external voltage regulator?

[slikside]

Originally Posted by CG

This is a good thread. If there isnt already one like this over in FAQ this should go there. Nicely done guys, way to help out in an easy to understand way.


Mark

Just what I was thinking!