Mechanics

ALTNATOR NOT CHARGEING BIT CHECKED OK.

2000 Dodge Neon • 4 cylinder 2WD Manual • 140,000 miles

How do I bypass ecm voltage regilator in 2000 dodge neon? Im not sure where field wire from after market voltage regulator goes on factory voltage reg. And if I have to cut factory voltage reg wire to kill circuit so I dont fry the ecm? Please help befor I blow my car up. I love this car and only have had for couple months. Note this started after my alt belt broke.
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Creapn4life
January 28, 2011.




I also have ran a obdll scan on it and its comeing back with the fallowing codes.P0118, p1594, p0622, p0108, p0123, p0132, & all of these codes at the bottom say high input or system tovhigh. Replaced map sensor, coolant temp sensor, ambiant temp sensor put new batt connectors, + new ground wires. Fixed any bare wires. Alt + batt checked out ok off the car but today had checked on car and alt not putting out any charge. I just want 2 bypass ecm voltage regulator tell I can afford to get new ecm. Please help would be most greatfull.

Tiny
Creapn4life
Jan 28, 2011.
The voltage regulator inside the Engine Computer gives extremely little trouble. I can help you install a 1970s regulator but first, measure the voltages on the three alternator wires. The fat output wire must have 12 volts all the time. One small wire will have 12 volts and the other small wire must have less than that but not 0 volts. Those last two voltages will only be there when the engine is running, not just with the ignition switch turned on. Holler back with those readings.

Caradiodoc

Caradiodoc
Jan 28, 2011.
K I was able 2 test the wires on alt and fat wire was a lil under 12 volts and one of the lil wires was like 14 vlots and this is when batt at 100% charged and car running. Whats up with
that?
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Tiny
Creapn4life
Jan 31, 2011.
Not sure how you got higher voltage on the small field wire than what was on the output wire, but the secret is the voltage on the second small wire. It's going to be the same as the first small wire, less than that, or 0 volts. My bet is for 0 volts. That would mean the brushes are worn. If you find between around 4 - 11 volts, that circuit is working. In that case, suspect a shorted diode in the alternator.

Caradiodoc

Caradiodoc
Jan 31, 2011.
K well ill check it agian and ill have alt checked agian. I checked it in a rush cause its like -20 below zero out. Soo ill let ya know when I check it agian.

Tiny
Creapn4life
Feb 1, 2011.
Do u think charging system could cause sensor codes 2 throw

Tiny
Creapn4life
Feb 1, 2011.
Checked both lil wires both are reading high like jumping between 12 and 14.5 volts fat wire reading 11.5 volts. Whats with that is it my alt or ecu?

Tiny
Creapn4life
Feb 1, 2011.
Yup. System voltage that is too low can affect sensor readings, however, there is a set of conditions for a code to set. One of those conditions is that other certain codes can't already be in memory. As an example, you can get a high manifold vacuum reading from the MAP sensor by snapping the throttle while you're standing beside the car. The only way to get a high manifold vacuum reading for seven seconds or longer is if you're coasting with your foot off the gas. That's how the computer knows the car is moving. No pulses from the vehicle speed sensor is a legitimate condition when the car is standing still, but if the computer knows the car is moving, there had better be a signal coming from the speed sensor. If not, it will set a code. If there is already a fault code set in memory for the MAP sensor, there is no way to know what to expect from the speed sensor, so no code can be set for him.

Some codes will not set below a certain temperature, or unless the problem acts up for a required period of time. In the case of the alternator, the code will be "field circuit not switching properly".

Any code for something that could have an adverse effect on tail pipe emissions will turn on the Check Engine light. That includes charging system codes, but not because it will affect sensor readings. It's because low voltage to the injectors or ignition coil(s) could cause misfires and raw, unburned fuel in the exhaust. So the charging system won't CAUSE sensor codes to set but it could result in other codes being set.

Caradiodoc

Caradiodoc
Feb 1, 2011.
It suggests the field circuit is ok. What I think is happening is the circuit is switching on and off about 400 times per second. The percentage of on-time varies to vary average current flow through the field circuit. That's the way vcr power supplies work. Digital voltmeters take a reading, analyze it, then display the reading while taking the next measurement. Subsequent readings might be taken while the field circuit is turned off or turned on. This all happens multiple times per second and is why the display jumps around.

What we need to do is to perform a "full-field" test to bypass the voltage regulator. That involves grounding the dark green wire between the alternator and the voltage regulator in the Engine Computer. The best way to do that, if you can get to it, is to ground that wire at the back of the alternator while the engine is running, and measure the voltage on the output wire. That dark green wire can also be grounded at the Engine Computer but I don't know how hard that will be to access the connectors so you can back-probe it. It's in pin 8. The trouble is both connectors are black, but there is no pin 8 in the wrong connector. Each one has four rows of pins with ten pins in each row. Pin 8 is in one of the outer rows, third from the end. Just be sure it's a dark green wire.

If the two wires are plugged into the back of the alternator, it will be safer to ground the dark green wire there. The wrong wire is dark green with an orange stripe. On some models those two wires go through a small black plastic block so you can't tell which wire goes to which terminal. If that's the case, I can paste a copy of a procedure that might help identify the right terminal.

When you ground that wire, watch the voltmeter or the brightness of the head lights. You'll hear the alternator strain. If the voltage doesn't go up significantly, suspect a shorted diode in the alternator.

Caradiodoc

Caradiodoc
Feb 2, 2011.
K I just did a full field test and when I ground the dark green wire on back of alt it made the volts go even higher but I also checked both wires with meter and they both were just jumping in the 12 volt range what do I do now?

Tiny
Creapn4life
Feb 2, 2011.

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