Dandy. The place to start is by measuring the battery's voltage. If you don't have a digital voltmeter, you can find a perfectly fine one at Harbor Freight Tools for $7.00. Also look at Walmart or any hardware store. This article:
https://www.2carpros.com/articles/how-to-use-a-voltmeter
is useful if you don't know how to use the meter. Be aware they're using an "auto-ranging" meter. That is an expensive feature you don't need. If you need help setting up your meter or with reading it, I can help with that.
First, with the engine and everything else off, the battery should measure 12.6 volts. If it is closer to 12.2 volts, it's good but fully discharged. When it's that low, the head lights can still be bright, but it won't be able to run the starter motor. Charge it at a slow rate with a portable battery charger for a few hours. If the engine cranks normally then, and the engine starts, you may have a charging system problem that isn't recharging the battery. Regardless, when the engine is running, measure the battery voltage again. Now it must be between 13.75 and 14.75 volts. If it stays near 12.6 volts, we have to diagnose the charging system.
If you find the battery is at 12.6 volts, turn on the head lights and observe their brightness. Now try to crank the engine. Tell me if the brightness of the lights doesn't change, if they dim just barely a noticeable amount, or if they go almost completely out.
This next step is going to involve a helper. You'll need to measure the voltage down on the starter's larger terminal. For the most accurate results, the meter's red positive probe should be touching the copper stud where the fat battery cable is bolted on. Most people touch the probe to the copper terminal on the end of the cable. That leaves out one connection in this test, so it's much preferable to touch the tip of the stud / bolt instead. You're going to find the same voltage that you just had right at the battery. Hopefully that will be 12.6 volts. What's important is what that voltage drops to when your helper turns the ignition switch to "crank". The shaking can make it difficult to keep the probe in place. To address that, I use a small jumper wire to connect the probe to the stud. You can find a pack of ten of them at Harbor Freight Tools too for about $4.00.
When the starter system is working normally, the very high current being drawn is going to pull the battery's voltage down a little. The industry standard is to no lower than 9.6 volts. That's what you're watching for on this test, but you're doing it at the far end of the battery cable instead of right at the battery. This way we're testing all the connections too. Tell me what that voltage drops to during cranking. Also tell me if during that test the starter cranks the engine or if you just hear that clicking again.
So far I haven't mentioned the meter's black negative probe. Some of my meters have a spring-loaded "alligator" clip so it can be attached and ignored. When the negative lead is a probe like the red one, I also use one of those small jumper wires. That probe or jumper wire can be attached to the battery's negative cable, any paint-free point on the engine, or any paint and rust-free point on the body sheet metal. When it reaches, I prefer using the battery's negative cable. However, if you find in the previous test the voltage stays up well above 9.6 volts, move the negative meter probe to a spot right on the engine, then do the test again. This way we're including the battery's negative cable in the test. During cranking, now you're reading the exact voltage the starter motor is seeing, which is the most accurate value for diagnosis. If it comes to that, tell me what you find. Remember that value. Next, go back to the battery and measure the voltage right there and see what it drops to when your helper tries to crank the engine. Ideally both readings should be very nearly the same. If the voltage at the battery remains well above 9.6 volts but down by the starter it drops a real lot lower, there is a bad connection we have to find. That is actually rather easy, but it takes some time to describe.
Let me know what you find up to this point.
Sunday, November 26th, 2023 AT 4:23 PM