Today when I went to take it for a spin, I started off by jumping the car and got it running, but then when I went to put the top down, the battery died 1/2 way through putting it down. I then jumped it again and got it the rest of the way down and went for an hour long drive, averaging about 35 mph. Once I got home, I went to put the top up for the night, and immediately when I hit the switch to have the roof go up, the car died immediately. I am assuming this is an electrical short of some sort, but looking for conformation as I am very new to this.
Another thing I noticed while driving, whenever I hit the brakes, the
radio would shut off and all of the lights on the dash that were illuminating the speedometer, rpms etc would dim and flicker. Once I took my foot off the brakes, everything would return to normal and this would happen every single time without fault. Again, possibly an electrical short and maybe the
alternator not
charging the battery enough? As I said, this is all very new to me and I am looking to get my foot in the door by attempting to fix this car up!
I am unsure if the top issue and the brakes causing the
radio/lights to act up are related, but I figured I would include them in the same post in case.
Since you stated that you had to jump the car to get it running tells me that you have a defective battery. How old is the battery?
Johnson Controls makes
Motorcraft batteries, and they use a date code on their batteries that indicates when it was manufactured. Locate the sticker or stamp on the battery that has a string of letters or numbers arranged in a code. On a
Motorcraft battery, this is located on the side of the battery case.
As you can see by the date on the sticker, this battery was manufactured on November 2018 and might be nearing the end of it's usful life. Once you replace the battery, here is how you can test the charging system using a mult-meter.
The charging system consists of the battery and cables, the
alternator and an internal voltage regulator. The function of the battery is to spin the starter motor to start the engine. Once that’s done, the
alternator takes over, satisfying the car’s electrical demands and keeping the battery charged. The battery then acts primarily as a filter, keeping voltage spikes from damaging the car’s electronics. The voltage regulator rapidly switches the
alternator in and out of the charging circuit to provide the car with the correct voltage.
On the 12 volt system there are two important numbers to remember, they are 12.6 volts and 13.5 volts. 12.6 Volts: If you think your car has a 12 volt battery, it doesn’t. The 12 volt battery actually has six individual 2.1 volt cells, and when fully charged, the battery should have a resting voltage of 12.6 volts. If with the engine off, the resting voltage is less than 12.6 volts, the battery is low and needs to be recharged. Of course, it begs the question of why the battery is low. It could be that the
alternator isn’t working, or that the battery has reached the end of its useful life. 13.5 Volts: With the engine running, the
alternator should output a charging voltage that’s about a volt higher than the resting voltage, or about 13.5 volts. The exact charging voltage may be as low as 13.2 volts or as high as 14.2 volts.
Take a multi-meter and set it to measure DC voltage, then measure the voltage across the positive and negative battery terminals with the engine off. On a 12 volt system, a fully charged battery should read a resting voltage of 12.6 volts. After you start the car you should see a charging voltage of about a volt higher than resting voltage. If the reading doesn’t increase by about a volt or if it stays at the resting voltage, it means that the
alternator isn’t recharging the battery. This could be because the
alternator is defective, the regulator is defective, or the wiring between them has failed. If the battery runs down enough that the ignition stops firing, the engine will stall. It’s really important that you don’t simply jump-start a car with a
dead battery without checking to see if the
alternator is charging.
A basic charging system health test: Use a multi-meter to measure the resting and charging voltages as described above. Then, with the engine running, gradually increase the electrical load by turning on the
headlights and the blower fan. Then increase the engine RPM to about 3500 as you watch the reading on the multi-meter. If the voltage stays about a volt higher than resting voltage, then the car’s charging system is functioning. But if the voltage drops or increases dramatically at any point, there’s a problem with the
alternator or the internal voltage regulator.
doug7740
1955 Thunderbird Blue
