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Discussion Starter · #1 ·
Alright, I've got an 89 escort lx with theinternally regulated alternator and it doesn't charge the battery, took the alternator to get tested and it passed, bought a new battery, bought a reman alternator and still nothing. I even tried directly wiring the alternator BAT terminals directly to where the battery cable attaches (on the drivers side fenderwell) and still no luck.

I'm at a major loss here, anyone know what could be causing this? As I said the Alternator tested ok and nothing changed with the new battery. I couldn't find a detailed schematic in my service manual, is there a way to get the bat wires reversed? They look like they go to the same place anyway. I've removed the ac as well and gone to a smaller belt. Does anyone have a shemati. Showing what the wires going to the regulator do?

Someone help please, I'm at my wits end on this one. Also the voltage stays around 12.5 or so, whatever it starts off at and slowly goes down. If I rev the engine it dips to 12.3 or so and then goes back up to about 12.49 or so, measurements taken at the battery.
 

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Have you checked the condition of your battery cables and the wiring going to the alternator? Check for cracked insulation, broken wires, loose/dirty terminals at the battery and ground.
 

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Discussion Starter · #4 ·
Thanks for the quick replies, fellas.

I'm going to go out and make sure all of the cable connections are free of corrosion and tight. I've looked at the wires to the alternator and best as I can tell, they are undamaged. As I said earlier, i also tried wiring the alternator bat wires directly to the junction point on the drivers side fender well.

Does anyone know what wires do what? There are two batt wires (black with orange stripes) and one small white wire with black stripe going into the side of the alternator, and then there are 3 wires going into the regulator on the back a white with black stripe (same one that goes into the side), a green with red stripe and a yellow with white stripe. If i knew where these were supposed to go, maybe i could try running new wires and eliminating the harness from suspicion.

thanks again.
 

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Discussion Starter · #8 ·
Alright fellas still stuck on this one. So far - new Neg bat cable, checked that the engine groundstrap was still in place, replaced big alternator plug. Still no charging - any other ideas?

Does anyone know what the wires of the smaller alternator plug are supposed to go to? There is a green wire with red stripe, a yellow wire with a white stripe and a white wire with black stripe (this one goes to the big plug). If I knew what these were supposed to go to, I could check them out.

Still stumped on this one and need the hive mind's help.

Thanks again!
 

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Discussion Starter · #10 ·
That is very helpful, looking at this, if the dash indicator were taken out of the equation do we think that would keep the alternator from chArging the battery? Does that wire do anything except light up the idiot light of it isn't connected? Also, do the small connectors ever go bad? Haven't replaced that one yet...
 

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Those smaller wires are for the field coils...they essentially create the magnetic field that cause the charging, and then you have the larger output wires (which you replaced the plug on). The small wire on the output side is going to be for voltage monitoring and feedback to the field side, so the alternator is semi self-sustaining without a battery.

The whole idea behind field coils is great because a permanent magnet is only so strong, even in rare earth form. The magnetic field created by the field coils is much, much stronger than any solid magnet, and it's variable by how much voltage is fed to it. A full shunt to the coils will cause the alternator to output approximately 18 volts at full amperage. To do that with a permanent magnet generator would require a huge one, as typically found on a school bus. So the alternator is more efficient (alternating current charge, hence the name) cooler running, and puts out more power in a smaller, lighter package.

Sorry, had to give the explanation.
 

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No, the idiot light simply runs off the charging feedback circuit. It will come on brighter the closer to 12 volts the charging system gets. It's essentially a volt meter in reverse. If you want to check how well the charging system is working, I suggest installing a volt meter to monitor that. It's simple to hook up.
 

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Discussion Starter · #14 ·
I've for a volt meter installed right now, that's how I found out I had the problem in the first place.

I'm really trying to get this figured out and it seems like the problem must be in the small plug, as that's really the only thing that's still original.

Does anyone know what type of signal/voltage those wires are supposed to see?

Amy other ideas?
 

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I don't know off the top of my head, but I'll be checking the shop manual and electric specs the next I have a free moment, hopefully tonight. 9 hours of work + 2 hours of driving doesn't leave much time for anything during the day.
 

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Heh, that's just for work..I have other stuff to deal with as well, including trying to do my own projects....no worries, though, I should be able to find the info relatively easily once I look.
 

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Discussion Starter · #18 ·
Got it figured out - For future reference that small idiot light wire (green with red stripe) actually has to see 12volts for the alternator to work, now we're charging at 13+ volts.
 
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