I've done a search on this topic and got a few good ideas but I still have questions. Here are the specifics: It's just a basic hot rod electrical system with no accessories. It has a Ford style starter relay, a one-wire alternator, and an electric fan. It's been on the road for two years now with no electrical issues of any kind and everything working so I know it's wired correctly. Lately it's been draining the battery. I had to jump start it on Sunday, and then I drove it all over the place at highway speeds and the voltmeter indicated 13.5 - 14 volts the whole time, as it always has. So I ***ume it was charging. I didn't drive it again all week and yesterday (Thurs) the battery was drained enough to not start the car. My first question is, with the key in the OFF position, should all of the posts on the back of the ignition switch light the test light? Shouldn't at least one or two of them be dead? Same thing with the Ford starter relay, all of the posts light my test light. Shouldn't at least one of them be dead with the key off? I did remove the - battery cable and clipped the test light to it and touched the probe to the battery post and the light did not light. I did take the alternator up to the local parts store and the guy put it on their machine and said the diodes might be bad, but he wasn't sure. But for five bucks I bought a new diode set and put it in. I'm still concerned about the ignition switch lighting up the test light though. What do you all think? Thanks in advance for anything you can suggest.
With a system thats been running fine for years, I would first suspect the battery. If thats good. Let the smoke out it'll run fine then. Unhook the battery during the times when your not running and see if it behaves the same.
Electrical systems are not my strongest skills but here goes. If the alt checks out ok on the tester, have them test the battery as well. Does the battery get stone dead if left without starting? If so something is draining it. I would one at a time disconnect all your accessories and see if thats the culprit. I've seen bad brake light switches draw off a battery. You say your voltmeter shows enough voltage; you need to get a tester on there and make sure its charging enough amps also. As I said, isolating if batt and alt are good will find the culprit. Let us know what the problem turned out to be. Hope this helps ya. "you can't fool with the law, Milner"...officer Holstein
well to start with, if ALL the posts on the relay were showing voltage then it would be trying to start. No not all of the posts on the back of the ignition should be on when the key is off. There should only be one "supply" wire that is hot all the time. If you have a switch with ACC. , RUN and START, then those terminals should be off when the key is out, but... just because voltage shows up there doesn't necessarily mean that the switch is the problem... it could be later on down the line somewhere. Are you sure that the switch is actually in the off position when the key comes out? I've had some worn out switches that would let the key out before it was actually turned all the way off. After that I would disconnect the "run" wire and measure the voltage without it connected to the switch, if that has no voltage then repaet with the ACC, then the start. If none of them show voltage with them diconnected, then the switch may be bad. If one of them does... then your problem is somewhere down the line. let me know what you find out..
What are you touching the probes to when you are testing the switch? and which battery cable did you take loose? When you try to start and the battery is dead, do the cables get warm or hot? if so you have a ground problem. That sums up my expertise on wiring without my Tex Smith book with the ragged ears.
when your car is off unhook the battery and if you see a small spark or hear a cracking noise you have a draw if not it probably is the battery if your alt has tested ok.
Have you tried a parisitic drain test on the battery?? I mean with a multimeter not a test light to the battery. Thats where I would start....
***uming it is draining the battery while it is just sitting narrow down the problem like this: Disconnect the ground wire from the battery. Put a voltmeter between the ground and the battery post. It should show a little voltage (that's what's draining your battery). Pull fuses one at a time. When pulling a fuse allows the voltage to drop to zero you've found the circuit where the mystery drain is.
The posts on the back with the wires bolted on them. Negative It's hard to be sure because the battery is under the p***enger side seat, but I don't think so.
First thing I would do is get yourself a VOM (Volt-Ohm-Meter - otherwise known as a multi-meter). If you think it's too expensive just order the $3 one from harbor freight - they actually work fine for this case and will give you MUCH better results than a nearly binary result with a test light. OK - now that you've got your VOM - with the car off - put the VOM on a 20v scale and leads across the battery itself - check the battery voltage - what is it at rest?? (should be 12.x volts), next have someone crank the car and watch the battery voltage - shouldn't drop more than a volt or two - 10.x volts is about the lowest you want to see. If it starts too fast then pull the coil wire or power to the ignition to make it crank but not start - if it's low on either test then get a battery charger - hook it up and charge the battery fully and re-test. If it's still low the battery is toast - replace it and be happy.. Next start the car and run it up to around 1800 RPM - you should now have 14.5-14.7volts at the battery - this is the charging voltage of the battery. At the minimum it should rise 1.5volts above the "at rest" voltage (unless the battery "just" came off the charger then the at rest voltage may be close to 13v.) If the voltage goes up then you're good on the charging voltage. Next have someone turn on all the accessories - headlights (high beams), heater fan, brake lights, anything to draw current from the alternator - watch the voltmeter - if it drops more than .5 volt then the alternator can't keep up with demand - it's either under-sized or not delivering current for some reason - have it replaced or rebuilt. Next - shut everything off, pull the negative battery cable off and put the meter on the 10Amp setting - and put it betwen the cable and the battery - read the current draw - should be under .2amps ideally. If it's higher than that start pulling fuses one at a time and see if the currrent drops off - if one fuse does it then start looking at the items on that circuit. There's a lot more - I'm tired of typing right now, so do some of those and report back
I will and thanks. Unfortunately, due to family obligations and a non-H.A.M.B. related Mustang club event it will now be Sunday before I can devote any more trouble-shooting time to this. I do have a multi-meter and right now the battery only shows about 9.5 volts. But I'll try those other tests you suggested. Thanks again.
Ok - time to get out the battery charger - if it's even moderately newer it'll have an automatic "trickle charge" mode so that it doesn't overcharge. - pull the negative battery cable - Hook up the battery charger tonight, unhook it tomorrow AM - then on sunday - get out the VOM and read the voltage on the battery before starting any troubleshooting - if it's low (and I suspect it will be) then the battery has lost a cell and needs to be replaced. If it's good start troubleshooting.
It may be your alternator.....have seen this problem a few times, especially with late 80's and up GM pickups. The reg malfuntions in the Alt, always charges fine, but doesn't 'shut off' when the Ign is turned off......so it's 'pulling' juice from the battery at a small rate.....
another quick test is to turn the headlights on before starting. Start or try to start the car, if the headlights or int lights go dim then 9 times out of 10 it is the batterys fault due to a bad cell.
Here's a follow up: Things don't always go as planned and I didn't get to do as much work on this problem last Sunday as I'd hoped. It wasn't until this past Thursday that I really had to time to dig and do some troubleshooting. I noticed that the turnsignal flasher was clicking each time I touched the battery cable to the post. Touch it, click. Remove it, click. I hooked up an ammeter as a couple of you suggested and there was definitely a draw. So I pulled the flasher and the draw went away. Put it back in, the draw was back. So the flasher went in the trash. I charged the battery, reinstalled it in the car, and then intentionally let it sit until today. I just went out and it turned over and started right up. Voltmeter reading 14+ so I think that was it, and I'm pretty sure the problem has been solved. I want to thank everybody who offered help and advice. I'm pretty good at the mechanical stuff but electrical has always been a weakness for me. So thanks again, the H.A.M.B. continues to be the most valuable resource.
My questions are, why was there power for the flasher for the turnsignals in the first place? The power to this flasher should be keyed on not straight off the battery. Unless the hazard lights, if you have them, and the turnsignals share the same flasher. What happend when you replaced the flasher with a new one?
The hazard light and turn signal's circuit do share the same flasher. But I have only headlights in the front so I never used them. I have not replaced the flasher.
I've always been taught to switch your dvom to amps first, making sure the amperage isn't too high to blow the milliamp fuse.Once you know it isn't high amperage you switch it to milliamps.Put the meter in series with the negative battery cable disconnected and you should have around 25 milliamps at the most.To find the draw start pulling fuses one by one until your amperage drops.If it doesn't then start looking at the alternator or starter
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