JohnnySC

I was leaving my place this morning, put the car in reverse and suddenly the radio went silent and the battery light came on. Then, later in the day, I was at a traffic light and the same thing happened. The second time I put the car in neutral and pushed the gas a bit and everything was back to normal. Any idea what the deal is? I assume it is batter/altenator related. Thanks in advance.

carnal_c30

hmmm is the car starting fine?

check the power of your battery, like jump it and see if the batter charges well I think 14V is about safe, if its down around 9-12 you may consider getting a new battery

if the battery charges, then check the chraging system and alternator for problems

Din

You may have an alternator problem I had this same problem happen to me. I replaced the alternator.

SC400TTZX003

Try this way. Start your car and open the hood. Disconect one of the battery pole (+) or (-) if your car still running---- go to find new battery, if Eng stop get new altenator. Goodluck!

strongsail

If you do what SC400TTZX003 suggests you will most likely destroy your alternator. NEVER NEVER disconnect the battery with the engine running!

If your battery is over a year old, get a new one. With a fresh, fully charged battery and clean battery terminals, if your battery light still comes on at idle, your alternator is probably failing.

Din

When the car is running it is running off the alternator isnt it? I didnt know teh car runs off the battery> I thought the battery is use to start teh car only.

bizzy928

If its over a year old?

Batteries start going yukky after 4 years. If you replace every year you are just wasting your money

strongsail

Batteries can be damaged by being undercharged - if the alternator is starting to fail and isn't keeping the battery fully charged, the battery will sulfate - that means the normal lead sulfate "fur" that forms on the plates as the battery is discharged aren't driven back into solution in the electrolyte as the battery is charged. That sulfate "fur" will harden and then it can't ever be driven off into solution again - and the battery is toast.

If you connect a new battery to a failing alternator, the battery will be history in a couple of weeks. Believe me.

And a bad battery will prevent you from figuring out what is really wrong. That's why I say, REPLACE THE BATTERY FIRST before you attempt to troubleshoot the charging system. It's one of the least expensive parts of the system, and the old one probably needed replacing anyway.

Just trust a marine electrician with 2 decades' experience on this one, okay?

2Lexus430s

You might want to check your Power Steering pump as well as your alt..

There is a Temp regulator on your Alt that controls how it charges... If its the problem I think your having, the Bat lights probably comes on after the car warms up or if it is hot. What happens is that your car stops charging when it reaches a curtain temp. This means you have to replace your alternator. The problem might have spawned from a bat power steering pump leaking fluid on your Alt.. Have that checked as well. The reason the light goes off when you are driving is because the fan is cooling it down. I had the exact same problem.

strongsail

TealLexusSc400 is right. Most internally regulated alternators include a temp sensor that will trim back the output if the alternator is running hot - and the regulator does this by lowering the voltage. A good alternator connected to a good battery (see above) will put out around 14V. Resting voltage of a good battery (see above) is 12.6V. When my battery light came on and I checked voltage at the battery with the engine running, I got a reading of 12.75V - slightly above fully charged resting voltage, but not nearly enough to fully charge the battery.

This gradual failure, I think, is a result of the insidious PS pump leak. Fluid from the pump leaks onto the alternator, and over time will saturate the field windings of the stator (the part that doesn't turn). The fluid will soften the insulation on the windings, and the windings will gradually go to ground (sort of like a dead short, but not exactly) and the alternator slowly dies.

Skulinex

ok, if that was the case, is there a way to prevent this from happening again after you have replaced both pump and alternator? like lets say a DIY shield or something to avoid the pump fluid to get to the alternator again?

strongsail

Good point.

When I got my pump rebuilt at 85K I was told that the rebuild kit included seals of better design and it will last longer, but who knows - any owners of high-mile SC's out there that have had a ps pump fail twice?

I think I'll lift that last paragraph and start a new thread with it and see what we get.

TeeDub

Bumped this to the top because it is the closest to my problem...

Drove from Oklahoma to Dallas yesterday with no issues (about 4 hours). After getting to Dallas, and being stuck in bumper to bumper traffic for about 20-30 minutes, my battery light came on..

BUT only at idle. If I ran it to about 1000-1100+ RPM the light went off. Finally after much butt clenching, I got out of traffic and the problem "disappeared" until the RPMs dropped again. Finally reached my destination and let the car cool for a while....

The problem did not reappear after letting the car sit for about 45 minutes-hour. (read: letting it idle/driving for about 5 minutes.)

Other than clean the terminals (which is about all I can do with the tools/parts I brought with me) anyone have any suggestions as to why/what was happening?

Dx3

iTrader: (13)

LOL, good answer!!

TeeDub

Great answer if the battery wasn't only a year old.

Car never stalled, hiccupped or had any noticable problems... (Of course, when the light came on the first time I immediately turned off the radio and air.)