QuestionQUESTION: Hi Roland.
Hoping you can help. My husband and I are at the end of our ropes with our 95 Dodge Intrepid SE 3.3 L V6. O Reilly auto center first said it was the alternator so we bought a new one, then they assured us it was the battery and bought a new one of those also, and nope. Last possibility was a new computer for the car. Purchased one for that too. Still won't stay charged, and it runs down quite fast. What is wrong with my car? I don't know what to do. This is my only transportation to drive my kids around.
-Misty
ANSWER: Hi Misty,
Chances are that one of the interior lights is on all the time (glove box, under the hood, in the trunk). So look carefully to see whether those bulbs are truly going off when the door is closed (you may have to get in the trunk to verify that, so be sure to have a trusted helper who will let you out!) If you verify that none of the lights are staying on after you leave the car then it is a matter of finding out which other electrical circuit is drawing away the charge on the battery. I assume that when you drive the car the electrical discharge light is not "on" or if you have a voltage meter in the instrument cluster that it reads about half-scale. If not then there is still a problem with the alternator/charging circuit, so let me know if that is the case.
The approach is to use an ohmmeter to measure the resistance that each of the main fuses is supplying current to.
If you can get a hold of a volt-ohmmeter with a digital readout you could differentiate between a too low (but still not 0 ohms resistance reading which is of course a short circuit) from moderate acceptable resistance such as 200 ohms or more. The higher the resistance reading the better. One of the fuses is supplying power to a circuit with a too low resistance and that is why the battery is running down. Begin with the fuses under the hood in the power distribution center box near the battery. One pin socket of each fuse is the "hot" side, which has 12V on it from the battery, so don't touch that one with the meter set to read in the ohmmeter position: first use the voltmeter to find the "cold" pin after removing each fuse. The 'cold' pin is the one to measure for resistance(i.e. all the lamps and devices are attached to that one). If you set the meter to read ohms (200 ohm full scale) and touch the - lead of the meter to any shiny metal body surface (or to the - post of the battery) and the + lead to the cold pin of the fuse socket it should read more than 50 ohm, the more the better. Make sure all the doors are closed when you are doing the measurements.
Then the question is how to find which of the many items on a given fuse pin that reads low is causing such a low reading. We'll get to that once you find the bad fuse pin.
So first go thru the power distribution box under the hood to find a fuse whose cold side reads less that 50 ohm, and let me know which one(s) it is (the label by number and/or purpose). That fuse will supply several fuses in the fuse box under the dash, so we will do the same testing on those fuses once we identity the 'master' fuse which is carrying too much current.
Then we can go on from there to isolate what component on that secondary fuse is drawing the current and check it out.
If you want to verify that you do have a problem with a hidden low resistance circuit you could experiment by disconnecting the battery overnight whenever you don't think you'll be using the car for a number of hours and see if it then lengthens the time before the battery discharges. Or you could get a meter which also measures current in milli-amps (mA) and remove the - post clamp at the battery and insert the meter between the clamp and the post to actually measure what the current draw is with the car shut down. It should be less than 100mA. But that will be a bit more expensive meter.
I will leave it to you and your husband to decide if you want to get the meter and do the testing. You should be able to find a digital readout meter for $10-20.
Roland
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QUESTION: Roland, thank you so very much for replying. It is something to do with the alternator, it is not charging the battery. But we have already replaced the alternator with a new one and it's still not staying charged. O reilly's said the new alternator is still only giving out 12 Volts and this is the culprit somehow.
ANSWER: Hi Misty,
So basically the alternator is not putting out a voltage greater than the battery voltage, correct, i.e. it is not charging the battery? If the alternator is properly connected to the battery (the thick black/gray wire at the alternator should show the same voltage as the battery itself shows) when the engine is not running, then the other things to check are:
That there is 12V on the dark green/orange wire at the alternator when the engine is running. Were that not the case then that would mean that dark green/orange wire is broken somewhere between the autoshutdown relay and the alternator. There is a splice along that path where it might be loose, or the wire could be broken internally. If there is 12V on that wire at the alternator post, then the only other reason it is not putting our a charging voltage is that the plain dark green wire located on another post of the alternator is not connected (i.e.,open,broken) between it and pin 20 of the engine computer 60-way plug. The motive for replacing the computer was the belief that it wasn't doing its job of controlling the voltage on that wire (it should be oscillating between 0 and 12V so as to turn the alternator on and off and thus produce about 15V true output so as to charge the battery). But maybe the O'reilly folks didn't check the condition of those two wires to make sure they were patent (e.g. connected and not broken). They should have done that before asking you to buy the computer, so if they find indeed that one of those two wires is open, they should give you back your old computer and refund the money you paid for the new one.
If your husband gets a volt-ohmmeter he can check this out by himself.
So the bottom line is: is there 12V on the dark green/orange wire when the engine is running or not?
and is there a good connection betweeen the plain dark green wire at the alternator and pin 20? One of those has to be no, given that you have a new alternator and a new computer, and of course a new battery.
Please tell me what he finds to be the cause. It has to be the wires I described above, unless it is a defective alternator.
Roland
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QUESTION: What should the voltage read at the field circuit plug to activate the alternator?
Where is the voltage regulator for the alternator on a dodge intrepid 95?
We finally did get the ohmeter and are trying to figure this out, just need these last couple of questions answered. Thanks a lot for your help again Roland
AnswerHi Misty,
The field coil has one wire at each end of it: A dark green/orange wire should have 12V on it compared to ground (the - post of the battery or the engine block will do) when the engine is running, and then the plain dark green wire should be at ground potential for the field coil to be activated (0V, BUT it does have to be gounded, not just disconnected. So if there is 12V on the dark green/orange and 0V on the plain dark green and you aren't getting any noticeable increase in the output voltage above that of the battery, then try grounding the plain dark green and see if that produces a voltage output increase as seen at the gauge on the dash, or if there is no gauge that the 'battery' light goes off.). The voltage regulator circuit is built-in to the engine control computer. As I told you earlier, that regulatory function is to ground the plain dark green wire in an oscillatory manner (on and off at a high frequency which frequency determines the voltage output of the alternator). I can't be sure but I believe that when the wire isn't grounded the wire may be at 12V (which because the other end of the wire is at 12v means that the field coil is not energized). So if you find the dark green wire to be at a constant 12V then that too would cause the alternator to not work. It is connected to pin 20 of the controller so you could check for continuity of the wire using the ohmmeter function. Please let me know what you learn.
Roland
PS: have you tried to get the readout of the engine controller memory for fault codes? "On-off-on-off-on and leave on", using your ignition key for that sequence, and doing it in 5 seconds or less. Then watch the check engine light to begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat for accuracy. Tell me the counts and there should be a diagnosis of the problem that way, too.
