O.T. Car electrical problem.

A couple of weeks ago my headlights started to flicker.A few days later the alternator went.Replaced the alternator and now it,s starting to do the same thing??The alt. is putting out 14.7v.And the amp output increases with load.Checked the wiring and everthing looks good.Any idea's.The auto parts store won't replace it until I can prove it's the alternator.Spoke to a mechanic and he said he thinks it's the vr.,which is built into the alt.

Al

Is this a Chevy, by chance? If so, I'd sure suspect that dimmer switch and/or light switch.

Same thing happened to me on a Yukon.

Allan

Make? Year? Model?

If the only symptom is flickering lights, consider the following:

Older Ford headlight switches have a built-in circuit breaker to protect the headlight wiring. The breaker automatically resets within a half-second or so to make it less likely that everything will go black at 60 mph some cloudly night. As the switch gets old, the breaker gets weak, and the lights start flashing even with nothing wrong. Replacing the switch fixes the problem for 5 years or so. There are mods around to drive the headlights with relays off the battery to avoid sending so much current through the light switch.

Dodge/Chrysler light switches are noted for being just adequate for the vehicle load, and tending to burn out if you try to add trailer lights without using the proper trailer-tow package with its separate relay.

Sorry, It's a 1998 Ford contour.

I have a similar mysterious problem with a '91 pontiac grand prix le. I was told to clean the wire connections on the alternator.

I replaced the steering column on this car and have all sorts of weirdnesses since, such as the speedometer works..sometimes..but turning on the heater can make the speedo straighten up or decide to go wonky again. I suspect a bad ground somewhere-i don't know where, and dont usually seem to find time to deal with this one problem.

Check the Ford Technical Service Bulletins. I'd bet there's something about your problem there.

14.7 is a bit high. It will overcharge your battery and kill it prematurely from lack of water. 14.2 is the optimum charging voltage for a starting battery.

Likely the alternator ground is one of those that isn't good.

Gerald J.

Some alternator regulators are controled by the VCM or ECM. Check all the connections.

Some of the nicest cars and trucks I've owned over the years have been vehicles that all hope was given up on. Haul them in and start checking electrical connections. I've had a 90% or better success rate of cleaning connections and grounds and making a dead vehicle run like new doing this. Of course some problems are actually mechanical in nature. Most vehicles 1985 to date have some sort or other of electronics. I'm no electrical genius by a long shot, but I did learn early on that a poor connection on a low voltage connection (ie; electronics) will drive you almost crazy. (high voltage connections are easily smoke tested). Just set aside a day with a spray can of contact cleaner, a white pencil eraser a shop manual and some patience. start unplugging every connection and lug you can find in a vehicle, clean up the contacts maybe apply a light coat of oxy-gard and plug/reconnect. You might be really surprised at the result. Most people won't take the time or are not that bright to do this and they won't pay someone else $65 bucks an hour either. I logged over 100,000 miles on a 92' Cadillac Eldorado and my daughter still drives. It's now at 208,000 miles I bought it for $350 And it was dead and hauled in on a rollback. The ECM connector plug had a tiny bit of corrosion. Cleaned the connector and the car ran like new and averages 21 MPG still.

Get an oscilloscope and record the waveform/output. Take that to them and see what they say. Then tell them to prove otherwise. It may be sticking (or worn) excitation brushes, or a floating rotor, or the avr is just nbg, or a poor contact in the voltage sensing side. May be other obscure causes like a dodgy drive belt.

14.7 volts is too much. It should be 14.4V. Your meter may need calibrating to prove that (but it might easily be 14.9V which is far too much voltage for any 12 volt lead acid battery at full charge). Digital meters often read too high when it's internal battery is getting low.

Check your battery electrolyte level if the charging voltage exceeds 14.4V as it will be electrolysing the water.

Regards, RAB

If it has the square regulator plug, look at the contacts in the plug and make sure none have a dark color, if they do replace the plug. If not, cut the blue wire going to that plug a few inches back , and put it on with the battery wire at the back of the alternator, so it goes from there to the regulator. That is fords fix for the cougars and such that have the same problem with the lights. jstpa

Depends when it's putting out the 14.7 volts and for how long. Also depends where you are getting the volt reading from. Are you checking at the alternator output post, from the battery, or where?

A typical automotive alternator with a built-in regulator can make voltage run up to 15.5 volts and still be working properly. That is only supposed to happen at high amp-rate charge situations though.

A typical system can spike up to 15.5 volts when a battery is highly discharged and there is a high-amp charge. It can also happen if there are bad connections somewhere. With normal start-run situations - first fast charge is normally around 14.6 volts and will come down to a "maintenance" charge of 13.4 volts.

I wouldn't blame your alternator until you either check all else - or isolate the alternator and test it properly. At the least - hook it direct to a battery known to be good.

A typical car battery (flooded lead acid) can handle a fast charge at over 15 volts just fine with no damage. If fact, when done right - it makes batteries last longer. It's not practical on a car or truck - but large battery banks are often over-volted to prolong their lives - usually called battery "equalizing."

Also, batterys in cold weather can handle a much higher charge voltage than batteries in hot weather.

I read something about this when I was looking for the same problem on my car,and a Ford pickup.The wires that plug in to the alternator are replaceable.Look them over good and replace them if you think they need it,maybe even if you dont.A mechanic friend told me the other day that if you dont replace them they might not warranty the alternator.Now I replaced 2 alternators on my Ford product 93 Mark VIII last fall.My car was running down the battery if it sat for a few days.Then if I drove at night the lights would get brighter,dimmer,next thing alternator would not charge except about 9 volts.After I put the 3rd alternator on(didnt know about the wires yet)I hooked up my battery charger,and went on about my business,working on other stuff,came back and checked it after about 10 minutes.It was not charging?Then as I watched the needle on the meter it tried to go up but there was a click and it quit.Hmmm,I check the cables(both are black) and Duh,I hooked them up backwards.Switched them and charged the battery up,been working since,knock on wood.Now I dont know for sure,but maybe?When I read about it a couple of months ago,it seemed like there were lots of people having trouble with alternators that were rebuilt is what they were blaming it on,and those wires,at least where I was reading when I Googled it because somebody else was asking about the same thing on their Ford F150.I dont know what size motor it was but it looks a lot like the one in my Mark VIII,a 4.6 V8.I wouldnt say hook it up backwards,but it makes me think I was lucky that it didnt fry something,and maybe got the circuit hot or something to where it worked.Could be wrong too.I have looked at my wires since then and they look brand new.I even took them off and shined them up with a wire brush on a die grinder where they were connected,That doesnt mean somethings not going on inside the insulation.That new kind of stuff they put on the roads in the winter around here is hard on wires too.