[ttopstang]

i just replaced the alternator and my battery still dies after 1 day of sitting.
anyways, i was on florida5.0 looking at the guages they have, and in the tech section, they said that if youve ever unhooked the instrument cluster then it makes it an open loop and your alternator wont charge anymore. then they said to fix it you take a jumper wire and connect a 12v ingition source to the light green/red wire.
i know my instrument cluster has been hacked into by the previous owner but can anybody confirm this before i go hacking into it myself.

 

[EagleAutosports]

That's something I've never heard of. Why would unhooking the cluster cause an open loop and kill the charging, I wonder? If it's true, I haven't heard of that. Maybe someone else has heard of it.

 

[Millusos]

i would like to know if thats true, because thats happening to me too, my car isn't charging, and i already replace the battery and the alternator looks to be ok, and a few days ago i unhook the intrumental cluster, so it may be true, i'll waiting for a answer too.:headscratch:

thanks for posting that question.

 

[EagleAutosports]

Any one verify this?

 

[Tominator]

Sounds bogus to me.

You might check the theory by putting an extra bulb harness between the ignition 12v and the green wire.

In the stock cluster there is a 300ohm resistor in parallel with the idiot light. The resistance of the idiot light triggers the alternator to charge. The resistor is there in case the bulb goes bad.

Many thanks to Member tmoss for my education in this matter almost two years ago!:shiny:

Won first in class at WFC9 thanks at least in part to him.:gringreen

 

[mnjarhead]

Doesn't make sense to me either. The alternator should charge through a voltage regulator directly back to the battery, no? I don't think there would be any reason for the current to go through the dash, especially since all the wires back there are little and the alternator wire needs to be big.
Do you have an external voltage regulator or is it built into the alternator? I'm not sure what they were doing in 87. If it's internal and you've replaced it just start checking all your connections and make sure there's nothing wrong. A multi-meter works great for this (way better than a test light because you can do everything with it).
Let us know what you figure out.

 

[ttopstang]

yea i only have an internal voltage regulator. im not too familiar with wiring and ohms, volts, etc. (the reason i asked) but i will have the instrument panel off tomorow and ill go ahead and try this. i dont know if it will work either. theres the page i read.
Florida 5.0 - Frequently Asked Questions

 

[Tominator]

When you disconnected the factory cluster the alternator circuit was opened causing the wire that energizes the alternator to be left open. In the instructions there was a special note about how to make sure the alternator would operate. What you will need to do is in the factory wire harness there are 2 wires that need to be jumped. You need to find a 12-volt ignition source and use the jumper wire that was in the electrical hardware bag and jump the 12-volt ign. wire to the Light Green/Red wire. What that will do is it will energize the alternator when the ignition is turned on. That will fix the problem of not having a charging alternator.

That's it exactly and as I explained the bulb/resistor only energizes the regulator, internal or external and no charge current goes through this wire.

After this takes place, the wire going to the dash has no current going through it and the light goes off when the motor is running.

 

[ttopstang]

so i shouldnt even waste my time

 

[POIZNES]

i am having the same problem i took out all my factory junk gauges and now my damn alt does not charge... it makes sense about the alt light having the diod or whatever in the back also the alt light is on a closed loop circuit on the back of the gauges going directy from the wiring harness back into the harness...

im going to try this tomorrow but this is about the only thing it could be since the only thing i did was remove my factory cluster and now the car doesnt charge!

good info on the site guys thanks:bigthumbsup

 

[EagleAutosports]

Let us know what happens, we'd like to know if this actually happens.

 

[spdjnky_42]

Im guessing that this only applies if you do away w/ your stock guages and use aftermarket. As long as you plug everything back together there should not be a problem. I just went w/ a 3G alt it charges directly to the battery instead of that loop crap. Worst idea Ford ever had....

 

[POIZNES]

yep works like new now... i think my wires were like a light green small wire and a red/green large wire think it is the 4 and 5 wire down looking at the plug on the left... you can see which wires it should be if you just trace your circuitry on the back of the cluster voltage jumped from 11 to 15 when i jumped them!

beware the idiot lights! lol... good info guys:nogrinner

 

[nicks_89_50]

same charging issue

I have read this thread and tried everything including running new wires from regulator and alt to battery. Still won't charge and replaced battery and alt twice. Any advice would help greatly. Don't wanna sell the car cause it only has 75k but getting grey hair. Thank you for any advice.