Was taking a test run to check out the tach and fuel tank patch. Car died and had to push it off into a parking lot (thank you officer for your help). Then walk a mile to get my van and go back and "fix" the car. Here is a little history 1) a while back car wouldnt start. Would start with a jump. Replaced battery (was mega old) pos/neg/starter cable. Started fine. 2) added a tach 3) Car set for a couple weeks, had to jump it today to take it for a cruze. 4) ran around for 20min or so and all was fine. Then the tach stoped reg RPMs, turns sig didnt work, and I tried the wipers slooow. Car started running rough and stalled. 5) unhooked the tach and AM radio (i spliced into the am pos for tach power). Charged the battery with the van for about 15min. Jumped started and got it the 1/2 mile home. 6) Would not crank when I got it home If it was not the tach or the radio, what are some common cuplrits to check for. Alternator? Ground? It is true you can pull the pos terminal to check alternator output? Thanks for your help
that one sure sounds like alternator to me! start the car and put a volt meter on the battery. should show something like 13 volts. 12 or under is a car with no charging system.
Sounds like a bad Alt and or voltage regulator...Never pull the + cable to test the alternator...Its a sure way to cook the alternator and will spike the regulator and kill it too.
Thanks for the heads up on the cable pull. Is there an easy way to tell which it is? Regulator Vs. Alternator?
If the alternator doesn't show a charge the accepted way to find out if it is the regulator or the alternator is to disconnect the regulator and momentarily jump from the field terminal to battery positive. This should show an overcharge condition. If the alternator charges then the no charge is being caused by the regulator. If charging is present but at a lower than normal voltage then you can test the alternator with the engine off. Disconnect the battery connection at the alternator and place a 12 volt test light between the wire you disconnected and the battery post on the alternator. (connect a lead to the wire and the other one to the alternator) If the light glows then there is a bad diode in the alternator and it should be replaced.
The complete trouble-shooting guide is here: Make sure the regulator is properly grounded - test it with a volt meter from the metal mounting flange to battery negative - it should be less than 0.5 volts. Check it with the engine off and running. Make sure the alternator belt is tight. Remove the battery + wire at the alternator and connect a 12v test light between the battery terminal on the alternator and the wire that you disconnected from it. If the light glows then replace the alternator - the diodes are shorted. If it doesn’t glow then proceed with the tests that follow. With the engine running…… With a volt meter (multi-meter on volt settings) place the Red lead on the alternator battery terminal and the black lead on the alternator case. You should see more than battery volts with the engine running. If you see a charge then move the black lead to the engine - the volts should be the same - if not then ground the engine to the frame and try again. If it still doesn’t charge then ground the alternator to the engine, Engine to the frame and frame to the battery negative. If there is no charge indicated, then disconnect the voltage regulator and jump a wire from the field to the battery terminal of the alternator and perform the test again. If it doesn’t show a charge then the alternator is bad. If it does show a charge then the regulator is bad - replace it. Note: most mechanics will replace the alternator and regulator together. They do this because they don’t trust their trouble-shooting skills or don’t know how to test them individually. It is not necessary to replace them both unless they both test bad. On the other hand the regulator is fairly cheap so if you want to replace them as a “matched set” and can afford the extra money - go ahead. It probably won’t hurt anything but remember - the box says the parts are new - not good. I have had many new parts that were not good right out of the box……
Thanks Paul!! I go the gas tank back in today, and noticed no ground from the block to the car. I grounded the battery to the fender. Now my ALT light comes on when I jump start the car. Does that automaticly mean the alternator or regulator is bad or does it still need to be troubleshot. IF I replace the Alt, i will spend the 15$ and replace the reg too. They both look just about original. thanks
You added a ground to the fender from the battery, right? You didn't move the ground from the engine to the fender.... you need both. Always troubleshoot first - there is no need to spend money to replace parts that are working.
Gonna try and track this charging thing down tomorrow. Battery is on charge now. What exactly doe "from the field" to the battery mean? Thanks again for all your trouble shooting tips.
Mine was doing the same thing, replaced the alternator and it doesn't seem to have the problem anymore.
The alternator has windings around the rotor - that is called the alternator field. On the back of the alternator the field connection is marked "Fld". Does that clear it up for you?
