Votage issues


Will webber1985

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Vehicle Year
1987
Make / Model
Ford ranger STX
Engine Type
2.9 V6
Engine Size
2.9l
Transmission
Manual
2WD / 4WD
4WD
Iam having votage issues got truck back from garge after having distributer put in. Was told to replace fuel filter because truck ran rough. But drove for awhile and realized wasnt fuel issue. The bucking got worse when I hit the horn. So i also tried turning lights on witch made worse. Same with heater fan. So any power draw on system makes truck buck and jerk bad. Took it back to garge to have alternator tested. Was told to replace so I did witch did not fix problem. So I cleaned all grounds up witch didnt help much if at all. Just this weekend my starter solenoid stuck open and wouldn't let starter disengage. So I replaced that. I cant figure this out and would love some suggestions on what could be causing this issue. Also truck has an internal votage regulator. Witch came with new alternator. Thanks for reading this and hope someone can help
 


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RonD

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First, do you have a Volt Gauge on the dash and "Battery Light", or do you have a AMP Meter on the dash, it will have + and -


You need a Volt Meter to test system further, shop should have done these tests, fast and simple
Set Meter to DC Volts, 20 or higher

Key off
Test battery voltage after vehicle has been sitting for a few hours, over night is better
12.8v is New Battery
12.5v is 3 year old battery
12.3v is 5/6 years old and time to shop for battery sale

12.2v, or lower, is drained or failing battery

Remember this voltage, exactly

Ground the meter's black probe to battery or alternator's case
Touch red probe to "B+" terminal on alternator, it has the larger wire(s) connected on a stud with nut holding it, usually on back side of alternator
Should see "Battery Voltage", the number you remembered :)

If not then you have a bad/blown Fusible Link(same as a fuse)
OR AMP Gauge shunt

Unplug the 3 wire connector on alternator(this is the voltage regulator wiring)
There will be a white wire, yellow wire and green wire
Put red probe on Yellow wire, should see battery voltage, exactly
If not then bad fusible link

Test green wire, should see 0 volts
Turn on the key, engine off
Test green wire again, should see battery voltage, this green wire is the ON/OFF switch for the alternator, so VERY IMPORTANT


If all wires test OK
Start engine
Test battery voltage again
Should now be 14.5-14.9volts, voltage regulator is in fast charge mode
After 5-8minutes of idling or driving without shutting engine off..............battery voltage should read 13.5-13.8volts, this is maintenance charge, keeps battery "topped up" but won't damage it, 14+ volts will "cook" a 12volt battery long term


If you don't get over 13.5volts with engine running then new alternator is bad, it happens
Assuming vehicle wires tested OK
 
Last edited:

Will webber1985

New member
Joined
Aug 6, 2019
Messages
5
Reaction score
0
Points
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Age
33
Location
03748
Vehicle Year
1987
Make / Model
Ford ranger STX
Engine Type
2.9 V6
Engine Size
2.9l
Transmission
Manual
2WD / 4WD
4WD
Thank you for your response iam going to test these thing when I get out of work today. Also the fusible links that are all over the place. can i replace them with an inline fuse ? Another thing is the garage replace a big gray fuseable link or over by coil and powerstering pump it had little green wire in and out. And the changed a diode in harness behind alternator that had two red in and one out cant rember color. But not sure if the got wrong amperage diode. But hope I can resolve this issue I drive truck everyday 100+ miles for work and sucks not have full power of truck when needed . Lol
 


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