Spiking charging system

[20862ls]

I need some major help!!! I have replaced the alt, batt, cables etc. and I still have voltage spikes. Help! Spikes to apx 17 to 18 volts and sometimes charges at 15.5 volts constant and returns to normal.

 

[4X4HIGH]

What year are we dealing with? Check ALL ground cables and engine to chassis straps. If all of that checks out then you have a bad voltage regulator. I don't care if it's a new alternator or not electrical parts do go bad and some are bad from the get go.

 

[20862ls]

will do. I have put 2 alts in it and barrowed a new batt from a friend and it is new and never used. is there any ground that is most likely the problem?

 

[Fordum]

If you have the alternator with the built in regulator, it should be simple to troubleshoot. Make sure the ground cable from the battery is good. If the engine cranks ok, then it should be.
Then, run a fairly heavy cable from the alternator housing to the negative post of the battery and see if that fixes it. If so, then you have a problem with the ground connection of the alternator.
It could be where it mounts to the engine, or where the engine mounts to the chassis.
Or somewhere in between.
Once you find where it is not making contact, you should be home free. Leaving the cable hooked up would work, but only as a last resort.

If you have a remote regulator, you need to run the ground cable to the regulator housing. If that fixes it, check where the regulator is mounted and find out why it is not grounded well.

However, not to be insulting, but are you sure that the voltage is doing what you think it is? Do the lights get real bright when it shows 15 volts?

You need to have readings from an independent volt meter. The one in the dash might be lying to you.

Some of them have a zener diode in them to make them an expanded range meter, and if it starts breaking down, it will read all kinds of wrong voltages.

J.

 

[20862ls]

Yes it is showing the voltage I am saying, I put my fluke on it. I will check the ground as you ask. Just to give you an idea of what I am, I work on locomotives for a living, and deal with electrical issues all day. If you have more in depth checks let me know. Thanks

 

[Fordum]

Ok, cool. I never know what level of expertise I am talking to.
Then you see where the regulator has to have a ground reference in order to regulate.

If its the built in one, then it gets it through the body of the alternator, the mount it sits in, the bolts that hold the mount onto the engine, and the grounds that couple the engine block to the chassis.
Assuming that the ground wire from the battery is tied to the chassis.
I tend to run it straight to the block if I have a reason to change it.
Since the biggest load is the starter, 200 to 400 amps generally, and since the starter is bolted straight to the block, then I usually just go straight to the block with the ground wire.
The factory often has different ideas and hooks the ground wire from the battery different places.
Why they never ask my opinion, I'll never know.........<G>


J.

 

[20862ls]

Thanks I will check and see

 

[Capt.D]

Ok, cool. I never know what level of expertise I am talking to.
Then you see where the regulator has to have a ground reference in order to regulate.

If its the built in one, then it gets it through the body of the alternator, the mount it sits in, the bolts that hold the mount onto the engine, and the grounds that couple the engine block to the chassis.
Assuming that the ground wire from the battery is tied to the chassis.
I tend to run it straight to the block if I have a reason to change it.
Since the biggest load is the starter, 200 to 400 amps generally, and since the starter is bolted straight to the block, then I usually just go straight to the block with the ground wire.
The factory often has different ideas and hooks the ground wire from the battery different places.
Why they never ask my opinion, I'll never know.........<G>


J.

I also run to the block and the frame just to make sure I have a good ground everywhere....