Can an alternator be making the correct voltage but still not be delivering a high enough amount of power (amperage?) to supply all accessories? I have noticed that after getting an engine back into a vehicle, after it sat for about a year, that the lights dim and the engine gets pulled down RPM-wise at idle when i turn on multiple accessories. Only thing changed was the engine. All other parts like the alternator were retained. For instance, if the headlights and fan motor are on, then I hit the brake pedal, it will dim the headlights and slow the fan. I have tested voltage at the battery and alternator terminals (at idle and higher) and it shows 13.5-14.7 volts. The battery always seems to crank the engine with plenty of power during starts, the system just seems taxed under accessory load. Any thoughts? Thanks.
Sounds like you could have ground problems. Make sure you have a complete ground circuit, battery to block, battery to firewall, block to firewall, firewall to frame. I know this sounds redundant but a complete ground circuit is important, run these extra ground wires and see what happens.
I'd verify your ground connection, if your negative battery cable runs to the new engine you might need another ground strap that connects it to your chassis.
What vehicle? Did you wire it yourself? Factory? Kit? Are any of the wires running off the alt, bat, starter solenoid or switch warm? What alternator is it? One wire? External regulator? Hate to answer a question with a question, but there's not enough info...
wtf? Anyways...the battery voltage will change depending on the load or charge from the rest of the electrical system. If the voltage at the battery is higher than 13 volts, and you're noticing things acting like they don't have enough voltage, then you have a voltage drop somewhere in the system due to lousy wiring or something. Measure the voltage drop from the accessory that's not behaving, and the battery, while the accessory is running. If you show more than a volt drop in the wiring, see if you can find where the problem is. Likely trouble spots include ammeters, connector blocks, fusible links, etc.
Jim's right, Pinkynoeg in post #2 will cause you to burn the meter up if you follow what he says. Now back to the original question. A lot of the older alternators had somewhat low output as compared to the ones we have now and only put out 35/45 amps which is fine if you aren't running a lot of extras. Start adding Halogen lights, heater on high blower and a sound system and the load exceeds the output at times. On my ot daily I have to run on low beam until the alternator gets the battery charged back up from starting as running on high beams, having the heater fan blowing and trying to charge the battery back up puts a full load on the 1971 35 amp alternator. Do check the connections and you might check the load that the accessories take to operate. You might find that some thing is drawing more power than it should.
I agree with all the above observations and recommendations (except the ohm/amp thing). I only want to add that what you are experiencing isn't that uncommon on older cars, even when they were new. Not only because of lower amp output capacity, but they didn't put out their full capacity at an idle. Better than a generator in that respect, in that they DID charge at an idle, but increased output with a modest boost in rpm. At least that's how I remember it..... Ray
my 66 chrysler is similar. when it is cold and the choke is on it is fine but after it fully warms up with all accessories on the lights dim and the heater blower slows at a stop/idle. it has done it as long as i had it (10 years) with no problem. i just thought it was normal.
What you are experiencing is normal. The alternator puts out more amps when it spins faster than idle. When at idle and you start turning more things on the motor will slow down because the alternator is trying to put out as many amps as it can thus creating a load on the engine causing it to run a bit slower. If you had an amp meter in your car you would see that at idle with all things on that you were showing a discharge on the amp meter but as the motor sped up you would see it start to charge more and put more amps in the system to handle the extra load.
Just a thought, did you change any of the pullys with the engine swap. this could slow the alt. rpms and not charge as much.
Sound like ground problems I've experienced before too! I also had a similiar problem with a loose/slipping belt in the same car! If I remember correctly the ground problem for me was with the frame to body ground. Just my 2cents!
Nothing changed besides the engine. All the same pulleys went back on the replacement. I am thinking it must be a loose ground. Perhaps block to firewall. I will re-check them all and make sure they are tight and clean. Thanks for the ideas.
Check block to the firewall, and also the + wire off the alt for good connections. Hey, here's another question: how does it crank? slow or fast? That'll help narrow
If you did any painting make sure to scrape those areas where the grounds attach. Hope you get it straightened out. Sometimes we overlook the obvious. Good luck.
If the diode triode is bad it could be charging at 2/3 output and will eventually drain the battery.. Just thinking out loud......
Yup...after checking all your ground connections if it still does it, have the alternator checked for max output. NAPA and several other parts stores will do it for free. It's also been said your alternator may not be capable of keeping up with the elecrical loads put on it with electric fans..fuel pumps, A/C etc etc...might need to step up to a higher amp alternator...the volt meter will tell the story. With all accessories and lights on, you should have at least a 13.5 volt reading showing on the voltmeter with the meter hooked directly to the battery. If not, step up to a bigger alternator.
Re; grounds,..... if you think you have enough of them,...add two more !! I always use the "star" type lockwashers on the ground connections,...as well as being sure they're connected to BARE metal..... 4TTRUK
You guys nailed it. Checked the strap from the block to the firewall. Ring connector on the firewall side was snug but still moveable. Wire-brushed everything for good measure and tightened it good and everything is back to normal. Thanks again.
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