New Alternator Question

[eyebuzz]

Hi All,

I'm back with new alternator questions - Just replaced my alternator (remanufactured one) and voltage regulator but didn't seem work out - same problem as before replacement - batter runs down, electrical stuff slows/dims/goes out. Jump started no problem but saw no increase in volts to the battery via a separate analog multimeter.

Questions:
1) When the truck is running should everything be able to run off the alternator exclusively - in theory could you disconnect the battery and it would still run? I ask this as when it was running and I started turning on lights, blinkers, heater blower all that electrical stuff was much dimmer/slower than normal and then the engine just died.

2) Can I test the alternator at the source using the multimeter (not at the battery)? If so what would I be looking for? What I'm trying to figure out is if it is the alternator that is bad (it's "new" but I know they don't always work out of the box) or my wiring. And If I can test at the source what would I be looking for on my meter - and what settings should I have it at (see photo below?



Thanks...I'm having a good time figuring all this out...BUT a much better time when it actually works.

[red71cheyenne]

Once you jump it to get it started, leave all the accessories off and check the voltage at the battery. You should read 13.5-14.5 VDC there and at the back of the alternator. If it reads that, then start turning on accessories one at a time and watch the voltage to see which one is causing your drain. Give us the results of the first test and we'll go from there.

[Allensracing]

how many amps is the alternator?

[eyebuzz]

Thanks Red71 and Allensracing... it is supposed to be 60-61 amps.

While the engine is running or off the volt meter reads exactly the same at the battery (seems to be about 11 volts) - so I don't think its any particular electrical accessory. But my thinking is maybe its the wiring off the alternator to voltage regular or ? Anyway, can I connect this meter directly to my alternator in some way and find out if it's working? If so what kind of setting should I have on it and what reading am I looking for?

Thanks, TT

[eyebuzz]

Originally Posted by red71cheyenne

and at the back of the alternator.

Sorry missed that part about the back of the alternator...I assume I just touch my positive end of the meter to the red wire connection at the back of the alternator and then the negative on a piece of metal?

[red71cheyenne]

Originally Posted by eyebuzz

Sorry missed that part about the back of the alternator...I assume I just touch my positive end of the meter to the red wire connection at the back of the alternator and then the negative on a piece of metal?

Right. Positive to the output terminal on the alternator and then ground the black lead to any bare metal. Should still read the 13.5-14.5 VDC with it running. 11 VDC is too low, the alternator is not charging at that point, so your battery is not charging and of course turning everything on will only kill it faster.

[eyebuzz]

Alright...looks like we are getting somewhere here...a test at the alternator shows it's about 7-8 VDC. I guess my only question now - does this make sense? Would a bad alternator still produce some juice - or would it just be dead?

[fixit-p]

Your alt is not charging at all, when you check you voltage with the engine off thats battery voltage and with the engine running it alternator voltage if there is no change then the alt is not working. The new replacement voltage regulators are solid state compared to the OEM units. It is important that the regulator be grounded if it isn't it wont work. Also do you have an idiot light dash or gauge dash? If you have the idiot light how does it behave does it come on with the key on?

[eyebuzz]

Yes, seems to be the alternator - when I test on right at the alternator I only get 7-8 volts (engine running). Have a gauge on the dash - but it shows no change running or not (it does work though)...thanks to all for the help...really appreciate it. Yes the voltage regulators grounded too (new unit there also).

[red71cheyenne]

Is this an internally regulated alternator or are you using the external regulator? You say this one was remanufactured, but has it been tested? If you pull the battery cable off like you were talking in the first post, it can kill the diodes in the alternator. 7 volts out of the alternator may be due to the regulator not kicking it up where its supposed to be, or the alternator regulator(internal) being shot.

I think the first thing I would do, is pull the alternator off and take it to Autozone or somewhere and have it tested. They will do if for free. If its good, then I'd check the external regulator to see if its working. They are not very expensive to replace either.

Let us know what you find out about the alternator and we can go from there.

[oldgold70c10]

If you have an external regulator alternator, check that the two terminals on the plug are actually making contact.

When testing, fast idle at about 2000 rpm so the alternator will be kicked in, these things sometimes will not output after starting the engine until it has been rev'ed up once, then they will output at lower speeds.

[red71cheyenne]

Originally Posted by eyebuzz

Yes, seems to be the alternator - when I test on right at the alternator I only get 7-8 volts (engine running). Have a gauge on the dash - but it shows no change running or not (it does work though)...thanks to all for the help...really appreciate it. Yes the voltage regulators grounded too (new unit there also).

Sorry, was too slow posting there. Ya, pull your alternator and have it tested. Its not putting out enough or the new regulator is toast too.

[Fitz]

You may have a CS130 alternator which is internally regulated but requires an external ballast resistor to activate the internal regulator. Look on the side opposite the large output screw for a 4 pin connector. It gets wired as shown in the diagram.