Electrical problems?

rnrjunkie said:

Right so I was cruising home froma meet last night. Everything as normal for about 45 mins, then the radio starts flickering on and off.. Worrys me, but I ignore it because it's cheap chinese electronics.

So I get into town, sittin at the light and she runs a bit rough...and then shuts off. Try to restart - nothing. Dead, just lights but no crank or anything. Push it off to the the nearby parking lot, try to start her again - nothing. Turn off the lights, and I get electrics back. Unfortunately my batter was too dead to restart, and just get that chattering sound you get when the battery is dead.

So manage to get a jump start, and she fires right up. I drive a bit, lights on as usual, until wham car shuts off again. Three mins. from home. Wife pulls up (don't ask) and jump starts me again. Starts right up. I think the problem is the lights, so I just run parking lights with the wife lighting the way from behind. Get home, pull into the garage, and turn the headlights on just for *****s n giggles. Car shuts off, I say goodnight.

Obviously the problem is related to the Headlights, or the current draw from them. Any ideas where I could start? Battery? Wiring shot? HELP!!!

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Hi,
I would start by pulling the H/L switch. They are a known temper-mental problem. There maybe a "short" going on. Unless, of course, there is something not right with the wiring attachments.
Good luck!

rnrjunkie said:

Hi and thanks for the quick response. Are the switches known to short out? I had replaced it about 1 1/2 years ago and have had no problems with it until last night.

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Hi,
Unfortunatley, It's quite possible it could be the switch as many of our beloved parts are made off-shore and not to the standards we used know. I would look for an OEM used switch. Google "JD Larsen" mustang parts. He carries a lot of OEM stuff. I'm still running my OEM switch after 47 years. Watch, now that I mention it, it will break!
Good Luck!

Hi, I would start with taking the battery and alt. in to a local parts store for a full charge (possibly 24hrs. to get a full deep charge) so that it can be tested properly. The battery could have a dead short, have gone bad or could have been overcharged by a faulty voltage regulator. If overcharged the acid normally smells like egg water and the sides bulge out. I would also take your alt. off (2 bolts and a couple wires) and have it tested on a load tester to see what it is putting out. Both these tests are normally free and will eliminate a big part of your questions for the cost of your labor and time. I hope they do this for free at the German parts stores too since you will probably be buying the parts from them, I loved it there when I got to go for 10 days vacation in '93. Would have stayed if I would have thought to look for a job....too young to think of it at the time.

If you have to change the alt. be sure to get a 65A replacement, that is the highest amperage this size alt. came in and it won't hurt to have extra, the VR will cut it down if need be.

If they both test good or either are bad I would replace the voltage regulator (drivers side next to the radiator) unless the store can test VR's also. It's a <$20 part and does wear out electrically.

Since the radio started first this is what makes me believe your battery is not being fully charged or not holding a charge as it draws about the least amount from the electrical system and would be cut off first. The headlights are the biggest draw on the cars electrical system so they go last and your spark plugs/coil fire from the same battery power so that is why the car died. If you had shut the headlights off while driving it would have felt like you gave the car a shot of nitrous by giving that extra 110Amps the headlights draw back to the motors ignition system.

I've had this happen on other cars. When the headllight switch goes bad your headlights will shut off until the switch relay cools then they will come back on for a short period until it heats up again, the knob shaft will also be hot to the touch when they shut off. I do not believe it is your headlight switch.
Jon

I wish 'car guys' would quite telling their friends to do this, pulling the neg. cable while running causes the electrical system to hunt for a new 2 gauge ground which it usually doesn't have an fries things in the electrical system anyway like the VR, alt., wires, etc. so if you didn't have an electrical issue before pulling the wire you do now. I sold a lot of electrical parts due to this 'test'...

Not sure how you would load test the alt. for voltage and amperage it is putting out without the proper tester/gauge, most handheld amp/ohm meters are not rated high enough to handle this amount, that is why the parts store straps it to a machine and load tests it which will read out both volts and amps put out. Same with the battery, you have to test to >500CCA normally, not a tester most people own.

I can have my alt. and battery out in 15min. and another 15 to the parts store, only costs me $1 in gas and i don't buy the parts unless they are needed due to the results of the test. I don't trust the test that they hook to your car running, introduces too many other variables - grounds, wires, etc. Once I know the part is good I work from there.
Jon

You can load test the alternator with just a hand held volt/multi meter.

This way isnt going to measure the max output, or give you a value for the actual current, it is just simply going to tell you if it is good enough or not.

You need another person, or a multimeter with long enough leads to reach inside the car, or over to the throttle on the carb, so that you can do it yourself, and preferably a tach as well.

start it up, with all electrical things off. Check the battery posts for volts.

at idle, turn your headlights on. check for volts, my guess is its dropping. slowly increase the load with heater blower, emergency flashers, etc. and watch voltage.

12.5 to 13 volts, the charging system isnt really doing anything, but neither is the battery.
13-13.5 Its kind of working.
13.5+ its charging

Below 12.5 its not doing anything and the battery is supplying power.

with everything on, slowly increase the RPMs until you get a MINIMUM of 13.5 volts

On my car, which has a known good charging system(per the fancy machines at autozone, etc), I wont get above 13.5 until about 13-1500 rpms. maybe a little more, well above idle speed.

Hey,
Congratulations on tracking down that fault. We all learn from doing.
Now, Happy Motoring!

Good job, trouble shooting can be fun IF you do figure it out...
Jon