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Hi Guys,
This seems to be my summer for alarm/antitheft problems.
Last night my wife called me from a gas station parking lot reporting that, after she got gas and attempted to re-start the car, the alarm sounded and the antitheft system disabled the injectors and starter preventing her from restarting the car. This vehicle has done this to me a number of times lately also. Up till last night, the solution has been to turn the key 2 clicks to the ON position, and then push a little back button mounted under the dash to deactivate the antitheft system and enable the truck to restart. This remedy did not work last night.
I ended up disconnecting and reconnecting the battery. This must have cleared the antitheft system, because I was then able to start the truck and drive home. On the way home I scanned the dash for any abnormal readings. I notieced that the battery guage was reading below the middle of the range, though it as not all the way down in the red. The headlights seemed a tiny bit dim but not too bad. The battery guage looked like it was reading lower than normal; even with the system loaded as it was last night (headlights were on AC (both front and rear) were on full blast, and radio was on.
When I got home I hooked up my voltmeter to the battery posts, and read the voltage with the engine running, and headlights and all accessories on. The voltage reading was 12.86. With the engine running and accessories off, the reading was 13.2. These readings seem low to me. So, two questions at this point:
1) Am I right? Are these readings low?
2) If so, can they have anything to do with the antitheft system lockout problems I have been having?
Thanks,
Pop
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The charging voltage should be between 13.8 and 15v, so yes, it is low. The first thing I would do is check the battery cables and grounds. If there is rust/corrosion it can cause high resistance that can be a source of voltage drop. Remove the center screw from each battery terminal boot and inspect the contact plates for rust and corrosion. Clean dirt, rust, and corrosion off with a wire brush and baking soda/water. Side terminal batteries are notorious for building up corrosion inside the terminal boots. Also check for rust at the other end of the negative cable at the block that it is clean and tight, and also the frame and body grounds for loose connection or rust also. Do a voltage drop test across the grounds to make sure there isn’t any resistance in the cable/wires. Check the battery positive wire on the post terminal of the alternator to make sure it didn’t come loose. If the wiring checks out, then the alternator is probably weak, but have it tested before buying a replacement. You can drive to an auto parts store and they can test the alternator while it is in the vehicle, or you can remove the alternator and carry it in to be tested. They can load test the battery also, just to make sure the battery is good. Even if the alternator is actually failing, it won’t do any good to replace the alternator if the battery is bad. The testing is free, so why not.
Well my voltage drops are too high on both the positive and negative sides. When I turn on all the accessories the post on the back of the alternator gets very hot, as well. There is even a spot on the side of the nut that turns bright red. The red-hot spot disappears when i turn the accessories off and reappears when I turn them back on. I will clean everything up (though battery contacts themselves are already clean) and report back again.
I was going to make a joke about red-hot nuts, but…
This does not sound safe. And I don’t know which nut you mean. A nut on one of the battery terminal clamps, or a nut somewhere on the alternator?
[quote=”Evil-i” post=138379]A nut on one of the battery terminal clamps, or a nut somewhere on the alternator?[/quote]
I think he means the nut on the alternator where the battery wire connects.Disconnect the battery, then undo the nut & stud connection at the alternator. Manually wire brush away any corrosion at all the metal-to-metal contact areas, like the terminals on the wires, the stud and the nut.
I’m assuming those wires have a crimped-on ring type of terminal. Check the wires at the crimp for corrosion, and inspect the last few inches of the wires for signs of brittleness or swelling under the insulation. You may have to cut off a corroded section and crimp on a new treminal. If you end up shortening the wire more than an inch or so, make sure there’s enough slack in the wire to make up the distance. It’s embarassing and frustrating to rescue a wire only to find it no longer reaches where it has to go.
This may not solve your initial problem, but this is an issue that has to be fixed before moving ahead.
If I have to cut off some corroded wire I can splice on new wire of the same guage to cure any resulting length problems, correct?
[quote=”popoften” post=138457]If I have to cut off some corroded wire I can splice on new wire of the same guage to cure any resulting length problems, correct?[/quote]
Yes, you can. Due to the amperage that goes through this wire splices must be soldered, and covered with heat shrink tubing or wrapped well with electrical tape.OK, I have had some more time to monkey with this.
The wire on the back of the alternator is fine — no corrosion. I cleaned the contacts between alternator and bracket, as I was getting some high negative voltage drop readings previously.
I put everything back together and took some more readings. Here is what I have found:
With accessories on and engine at ~1500 rpm:
1. Hooked black multimeter lead to neg batt post, red to pos batt post — reading is 13.7 volts
2. Black lead to neg batt post, red lead to alt case – 150 millivolts, which I believe translates to .15 volts.
3. Black lead to neg batt post, red lead to alt braccket – 130 millivolts, which I believe translates to .13 volts.4. Red lead to pos batt post, black to alternator b+ post: 240 millivolts, or .24 volts
5. Red lead to pos batt post, black to alternator b+ post nut: 260 millivolts, or .26 volts
6. Red lead to pos batt post, black to alternator wire lead: 230 millivolts, or .23 volts
7. Red lead to pos batt post, black to alternator b+ contacts base: 220 millivolts, or .22 voltsThere is no longer any red-hot spot on the alt post, but the whole alternator is very hot to the touch, hotter in the back than the front. It gets hotter under load, less hot when accessories off.
Oh, before all this today I had removed the alternator from the truck and had it tested at Advance Auto Parts. It tested out fine on their machine.
Any thoughts on what alll this means?
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