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Ramcharger w/failed charging system. Stuck and need help/advice.

Truck details:

86 Dodge Ramcharger SE, 360 4x4, auto, tilt, no A/C.

Problem: Charging system failure.

Symptoms: Electrical outputs diminished (things light light output, power windows and wipers are slow, etc). Increasing load on the system makes lights go dim, stereo to shut off, wipers to slow, and so on. Increasing engine or idle speed does NOT counter this effect, nor cause the system to come back up to full power. Vehicle doesn't start without a jump.

Tests: Before it died on me I stopped into a Schucks and had them do their electrical test. The result pointed to the alternator as the failure. I took the alternator in by itself (the first test was done in the vehicle). Two bench tests showed the alternator to be fine.

Next I tested the battery voltage with the truck off. Voltage was just a touch under 12v, yet I had to jump it in order to get it running again.

With the truck running I checked voltage at the battery again and it still read 11.4. Revving the engine did not increase voltage.

I then disconnected the voltage regulator and ran a jumper from the green wire connection to ground to perform a full field test. With the truck running again, I tested voltage at the battery leads and it read

  1. Again, voltage did not increase or drop with engine speed.

My manual indicated the voltage should jump to between 14 and 16 volts, and to only run this test long enough to get a reading. After I saw the voltage went up 13v but stayed steady, I feel I have ruled out the regulator as the problem. This is also still under voltage, correct? Normal voltage should be around 14v. Bypassing the regulator only bumped it up slightly.

Following the test procedure in my manual, I then disconnected the neg batt cable and then hooked up a test lamp between the negative cable and negative post. The light came on. I disconnected the alternator, and the light stayed on. The manual says this means there is a short.

Next, leaving the test lamp in place and the ignition off I started pulling fuses to find out what system the short is in. The light goes off when I pull the fuse at #7 (HORNS) and #9 (DOME STOP LMP). Is it interesting to note that the test light will come back on if I pull the headlight switch out?

Now we come to the crux. It would seem I have a short in both of those circuits. But do I really?

Here's why I ask.

The test lamp is acting in lieu of a direct connection of the cable to the post. I would expect that the test lamp would of course come on if I pull the headlight switch out because lights work even when the ignition is off.

The horn and interior/brake lights are also made to work when the ignition is off. BUT, I would expect the test lamp to be OFF unless I was doing something to close those circuits like honking the horn or actually stepping on the brake or turning on the interior lamps.

I pulled the leads to the horns, brake light switch and interior lights and still read voltage at those fuse slots AND the test lamp is on unless I pull those two fuses. I jiggled each of the smaller harnesses around hoping to see the test lamp blink off but no dice.

My manual does have the wiring diagram, but only shows the circuit for #9. For #7, 8 and 10 it only shows their presence on the fuse block, not their wiring.

So what do I do here? Does any of this make sense to anyone? Where else should I be looking or what else can I test?

Thanks, R(k)

Reply to
grimisme
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Has a similar problem with a ford ranger, turned out to be the cable running from the battery to the starter was corroded inside of the wiring. You couldn't see it with the naked eye, but when you cut the cable, it was all green and corroded. It will pull a load on the battery, even when not running ( like your 11. something volts indicate above) and will never let the battery charge due to the constant drain.

I'm pretty sure that's where your problem is.

Reply to
MoParMaN

Besides the charging system failure, it looks like your battery is also pretty much used up now as well.

Sounds like a lack of experience there to me. You have to be careful with some bench tests as well as depending on the equipment that they use they don't always show the entire picture.

Static voltage doesn't always give a clear picture. What was the voltage when it was cranking or rather, when you turned the key to start. As said before, it looks like your battery is shot as well.

Which as I assume you know, means no charging.

If the voltage jumped up when the regulator was bypassed, then it should be obvious what the problem is.

Then you would be wrong. The numbers in the FSM assume that nothing else is wrong and that is not the case here. A bad or severely discharged battery can clamp down the voltage to 13V and it could also be caused by a failed rectifier in the alternator. You could and probably do have multiple problems going on here.

I don't see how that could indicate a short. What it indicates is current flow which is normal. If you have an under hood light, a door is opened, a glove compartment light is stuck on, or just about anything attempting to draw power from anywhere in the vehicle can possibly light that light. What type of test light are you using.

No it isn't. Any time you activate something that draws power, that light will light. Now I'm not sure why your horn circuit would be drawing power unless you have something else connected to it but the dome light circuit indicates that you have a light on somewhere.

There is a big difference between a load and a short. If it were a short, then the fuse would blow.

And you would be correct which indicates that something on these circuits is drawing power and you need to find out what. If it were a true short, the current draw would blow the fuse. Now you might have a defective switch somewhere in the lamp circuit keeping a lamp on somewhere that is not normally seen like the glove compartment or some storage area or did you just forget about the dome light? As for the horn, did you connect some aftermarket equipment in the truck and tapped into the horn power for it?

You are looking in the wrong place as neither of these circuits have anything to do with the charging system. At best, you might find something that is killing the battery when the vehicle sits for a long period of time but this has nothing to do with the vehicle not charging.

The first thing I would do is charge up that battery and then have it load tested. If it is 5 or more years old, just replace it. Then I would check the connections on that regulator and clean them if they are dirty and if not, replace the regulator as it is not working. The jump in voltage from

11.4 to 13 is significant and shows that the regulator is not functioning. If cleaning the connections on the regulator and its connector causes no change, then replace the regulator. The fact that it didn't go above 13 could be caused by many things such as a bad battery or a defective alternator as well. I would also check the ground strap between the engine and the chassis. After changing the battery and regulator, if the vehicle is charging but still not getting above 13V, I would have someone that actually knows what they are doing check that alternator again with the proper equipment to make sure that it is capable of putting out full power or you will wind up in the same situation again in a short time.
Reply to
TBone

Check the voltage drop from the alternator to the battery positive post when hopefully you are charging or supposed to be charging the battery. Also the voltage drop fom the battery to the starter when starting the engine. Battery cables can go bad on the cable itself and not show any damage.

Bob AZ

Reply to
Bob AZ

Thanks TBone, this makes perfect sense to me now, if the battery was undercharged (was) and wasn't charging (true) then I was misinterpreting the test result as failed when in fact it was doing what was expected.

I bought a Niehoff regulator and charged up my battery and everything is back to normal.

Thanks much.

R(k)

Reply to
grimisme

Cables are all good, looks like it was the voltage regulator.

R(k)

Reply to
grimisme

Glad to hear it and your welcome.

Reply to
TBone

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