voltage drop
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voltage drop
Last edited by bsetbuilding; Feb 15, 2011 at 01:43 PM. Reason: picture didnt appear
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when i start the truck, turn the key to accessorie (to cycle the glow plugs?) sometime the WTS light flashes, sometimes not, when im starting the truck. the light does not flash when its running. when the light doesnt flash, the truck wont start. should the voltage at the pigtail be 12-14v ?
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That's a 1G alternator, the wires you're probing are the stator and field wires, do not mess with them at all. The stud is a grounding point, some older vehicles use it, IDI trucks don't.
When your voltage drops down to 12V with all the accessories on, does revving the engine up some also bring the voltage up? I'm pretty sure that what you're seeing is just a result of the fairly weak low-speed current output of the alternator combined with a fairly high load from the accesories - in other words there's only so much the alt can do at idle, and your current draws are adding up to more than that. Nothing unusual or odd about it, you need either a bigger alternator, or more engine speed.
When your voltage drops down to 12V with all the accessories on, does revving the engine up some also bring the voltage up? I'm pretty sure that what you're seeing is just a result of the fairly weak low-speed current output of the alternator combined with a fairly high load from the accesories - in other words there's only so much the alt can do at idle, and your current draws are adding up to more than that. Nothing unusual or odd about it, you need either a bigger alternator, or more engine speed.
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i havent messed with the stator wires other that to read the voltage. should they read 12 to 14v instead of 6.5 - 7.5v ? when i bought the truck i dont remember the wipers, headlights n such struggling at idle. i put appx 12k on the truck before replacing the alt, reg, and batteries. i replaced one battery 5-6 mos after doing the alt/reg and other battery. i had both batteries load tested out of the truck and one was still good. After further reading on this forum, i've learned that i should have replaced both at the same time. Also, if im reading .9 - 1v on that stud on the alt, should i cap it with a rubber boot ?
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Not sure on the voltage on the field & stator wires, but if everything worked fine at one point maybe it's your voltage regulator going out? You can also try adding a ground cable between the passenger-side battery and the alternator, I saw this on another IDI truck (done for a different reason tho) and so I did it to mine as well, a mechanic buddy says it's a good idea anyways cause he had a 3G-converted Mustang in his shop once for charging issues and it turned out the alt ground path trough the accessory brackets and the engine block and then the main battery-to-block cable was't quite cutting the mustard...
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i also read that if i dont have a good ground on the regulator, that might be it too. i will try both. this forum is the best !
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Oh yes, the VR needs a ground - the plate it sits on actually ain't part of the metal works of the truck, it's bolted to the plastic inner fender only - so there should be a ground running between one of the VR bolts and metal outer fender, IIRC the fender-side of it goes to one of the bolts that hold the starer relay on the fender. There may be a connector along this ground wire, so pull it apart and check for corrosion.
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From: Nutter Fort, WV
You may have a cab ground problem.
Not sure where the strap ground is located on the 89.
On my 86 it went from near the wiper motor to one of the intake manifold bolts.
If the alternator is putting out 14 volts but the cab ground is bad, your gauges in the cab and your electrical devices would act like low voltage since the ground path is interupted.
Electric has to have a good path to follow in both directions.
Not sure where the strap ground is located on the 89.
On my 86 it went from near the wiper motor to one of the intake manifold bolts.
If the alternator is putting out 14 volts but the cab ground is bad, your gauges in the cab and your electrical devices would act like low voltage since the ground path is interupted.
Electric has to have a good path to follow in both directions.
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With all the accessories on the voltage on the output stud drops to just over 12 volts. the wipers on high will barely move across the windshield. i will look for the cab ground. thanks again for the suggestions !