With heater on high, fan slows head lights dim a little as well as dash lights....have replaced alternator, battery is in good condition. this only takes place once vehicle comes down to a idle with the brake pedal applied.
This is normal behavior in Grand Ams. I've had a '97 and a '04 and both did this from day 1. You'll also notice the lights dim/blower slow down more if you press the brake pedal while idling w/ blower on high and lights on; it's just that the alternator on these cars can't output anywhere near full power at idle. (my '03 S-10 also does this). Watch your voltmeter if you have one, when running above 1200 RPM you should see the system running between 13.5 - 14.5 (usually you just have to eyeball this as the gauges aren't well marked, mine are only marked 8 & 18 - should read slightly past halfway). If you're still worried, have someone check the system for you, many places like Autozone or Advanced will do this for free.
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running or not , the engine, that be big time , important....??????
if running is engine hot cold (engine coolant, not air temp)
this is called bad power (12vdc) distribution.
or is the alternator failing
or is the engine RPM going to low, 800 is normal for most cars.
if not running, its a bad battery (or just discharged) or is corroded battery lugs (service them)
if engine RPM drops too low the Alternator will just cut out
and the 15v power is now 12. a visable dim can be seen.
causes running. are
1: alternator belt slipping, sure service it.
2: alternator regulator bad.
3: battery bad. or bad lugs.
if you have a voltmeter all this is easy.
your radio system is amplified sound system, the amp. is in the rear compartment under the rear window area, need to get the radio car system checked by a professional, they are a little bit complicated. as far as the heater same advice. the alternator and battery ,mainly keep the car going, battery for starting, alternator just keeps the electrical systems on your car supplied with power.
Sounds like you lost the charge from the alternator.
When the alternator quits charging your battery light comes on and your car will run on battery power only...and only for a short time.
As the battery gets its stored energy used up...everything that is electrical will get slow or dim.
I'd check your alternator for proper operation and its drive belt...
If you have a failing battery or alternator the lights may go dim on full electrical load. As a first course of action, I strongly suggest that you have the battery and alternator be checked before replacement.
Hope this helps and thank you for using FixYa! Have a good one!
Many auto parts stores can do a load test on your electrical system. This would give you a good idea if your alternator is doing what it should be doing. It does sound like it is losing charge when system demand is high, but even if the alternator is not putting out much at high demand, the battery should pick up the slack in the short run. I would have both of them load tested.
It shouldn't be. This would suggest that for some reason your alternator isn't performing at low speeds, especially if the problem goes away when you rev the engine up a little. I would check the connections at the alternator and battery to make sure they are tight and clean first. If you have to remove the battery cables to clean them be sure you know how to recode you radio first. That info should be in your owner's manual.
It could also be that there is not enough tension on your belt, or it could be the alternator itself. If the belt tension and alternator are both good, it should be putting out 14 Volts or a little better when the truck is idling.
You may also need to check the fan and the fan switch if everything else is good. They may be the source of the extra draw. Hope this helps.
If the battery and alternator tested fine. I would have the charging system rechecked when engine is hot and at high rpm's. This way the checks are being done as if you were driving and driving for a long time. Alternators can work fine when cold but weaken when hot or stop working. This problem is not rare but only is seen occassionly. Unless it was checked at an electrical shop the average shop doesn't run these tests for they don't see the problem often enough to automaticly run them at all times. Good luck and let me know how you make out.