Getting frustrated here.
Working on the challenge Fiero, car dies after 20-30 minutes and won't restart. Battery is dead. Recharge and car runs for 20-30 minutes, dies, no restart. Swapped battery and same thing happened. Pulled alternator and it checks good by two different test facilities. Can't find any broken wires, voltmeter on dash shows good all the time.
Anyone got an idea?
Have you ohm'd out the wires? Checked alternator voltage output at the charge lug? I wonder if either the wires are causing a drain that the alternator can't keep up with or that you have a wire misplaced from the alternator to the battery.
Wires causing a drain? Could you explain further?
Alt is confirmed putting out 95 amps. I am suspicious that it can't keep up with the demand of an electric water pump, fuel injection, and electric fan. Battery is about 9 feet away from the starter via a 4 gauge wire.
Check the battery voltage at the battery terminals with the engine running and all extras switched off or disconected, then do it again with all accessories running. If you cant maintain 13 volts with everything running and the engine running at about 1200 rpm something is wrong. If possible take your readings from the battery post, not the cable end or clamp, bad cable ends are out there. The point of testing with this method is to make sure that the connection from the alt to the battery is good. Another problem that I have run across is a failed internal juntion in the wire harness. IDK if that would even be possible with your car, but its worth checking. Since we're on the subject of open circuits, have you checked for burnt fusable links?
FWIW, I've always heard that power sucking accessories should be connected directly to the positive post of the alt, not the battery.
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If you have excess resistance, you lose amps. Then everything else drawing power is drawing on the battery and not the alternator.
95 amps is the bare minimum to run all that, but it should maintain the battery.
4ga, IMO, is small even for that short run. It may work for the factory brand new, anything I build is a size bigger minimum.
The fan is running through the factory harness as it was built. The water pump is getting power from a junction block in the engine compartment. All it's wires are less than a foot. Checked the fuse links, they are good.
Would a heavier wires from the alt and starter to the junction block help?
The 4ga wire seemed light to me too, off to get something better...
if 95amps is minimal, I shudder to think about turning on the headlights and wipers! Whats a challenge friendly alt upgrade without buying a different alt?
Have you done any voltage checks in car beyond observing the factory volt meter? I would go to town with a multi-meter to be sure the alternato is producing 13+ volts in-car and that said voltage is arriving at the battery.
The 4ga wire may be less than ideal but will not result in a charging problem you're describing.
95 amps is equal to 1140 watts. the ignition draws about 20 watts. electric fuel pump 60 watts radiator fan 200 watts electric water pump, maybe 80 watts all of that is 360 watts. alternator output is relative to rpm . Oh , the fuel injection system will draw about 100 watts. Still way under the rated outout. the battery should have 12.5 volts with no load. A load test by adzone will show a defective battery. Charging output at 1500 engine rpm should show 14.3-14.4 volts.
I was gonna say that I am running all that with a 45amp alt and I am fine.
I echo the question what voltage are you getting at the battery with the car running? That is the most important thing to know right now.
voltage seems ok, but my meter is not so good. The readings match my other car which is running fine.
Your voltmeter doesn't have to be particularly accurate to test whether you are charging. What is the voltage at the batt with the car not running? Now start the car- Is the number around 2 volts higher? Voltage is ok.
Shut off the engine. Push on the fan behind the alternator pulley. Does the pulley slip on the belt? If so, its not tight emough, or its worn too thin. Replace the belt or tighten it till you can turn the engine by pushing on the alternator fan.
Do you have clamp on battery cable ends? If so, take them completely apart and make sure there is good contact everywhere.
Where is the ground cable bolted to the engine, and is there a good cable from the engine to the body? Electricity must run in a circle. The ground side is equally important.
If the alternator is typical of 80's GM, there should be full battery voltage on the main red cable, plus with the key on there should be voltage on both the smaller wires as well. One of those wires is battery power, the other is the signal wire from the dash light or charge relay. If it doesn't see voltage when you start it, it doesn't know it should charge.
95 amps is way lots. For what anyone has in a race car, 50 will generally do.
come to think of it, the voltage would go up and down a bit, as if the alternator was shutting on and off. I'll assume I'm seeing the voltage regulator at work? The reading was higher with everything turned on! Was able to drive for a while and re-start. Cranked slow but did fire up. Idle was getting worse as time went on. Trying to get the car running right and chase this at the same time is not the best plan.
You keep saying that voltage at the post is OK. Can we get a number?
You need a load tester on the battery with the car running. HF has the Toaster type be fore WARNED it will smoke like you dumped a quart of oil on a hot plate the first few times you use it.
My guess is theirs a weak fusable link in the alt output wire, or a weak area in the feild wire so alt is not always working.
SlickDizzy wrote: You keep saying that voltage at the post is OK. Can we get a number?
+1
A number with a decimal point is crucial here.
One of the biggest problem areas when they occur between alternator and the battery are the battery terminals. Plus bad grounds.
Sorry, couldn't get into the issue today. Going to try and find a better meter.
Battery terminals are new.
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