Alternator Overheating?
- Thread starter jacob dehart
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
jacob dehart
Newbie
What amperage’s should I be seeing if I use a ammeter for the alternator?
jacob dehart
Newbie
I have owned the truck a year and only put 80 miles on it due to waiting on parts, fixing other things, and now what I have been stuck on is electrical. The previous owner had bought the truck and had it sit about 1 1/2 years. It has a 2021 inspection sticker. I have deleted 4 aftermarket front end leds that previous owner installed and wiring. I deleted a separate aftermarket switch he had installed for those lights. Deleted trailer break and all wiring. Deleted aftermarket tachometer and wire for that. Tried to get it back as stock as possible and in doing so I got everything to about 14.6 volts, beforehand when I bought the truck it would usually stay at about 11 or 12 and when I would turn accessories on it would often drop or even raise voltage. I do have a windshield brow with 4 running lights but I do not have it wired up. As to what I have done to the electrical system includes new positive and negative battery cables with the big 3 ground upgrade. Wired new dimmer switch. Fixed headlights through shorted and cut wires as before I had no running lights. New starter wires, new alternator wire, brand new alternator and battery. I have found multiple shorts and corroded wires that I have spliced mostly under the dash and on the motor. I believe the previous owner bought the truck and didn't know too much of what he was doing adding everything and maybe trying to fix electrical issues he had. Hope this helps
Also called "parasitic amperage draw or drain".
Never disconnect the battery while the alternator is charging. It's dangerous, (the spark from disconnecting the battery terminals can ignite hydrogen gas produced by the battery) and it can destroy diodes in the alternator from the voltage spike as the current (amperage) is stopped suddenly.
^^^ Wisdom.
I'm not saying there "can't" be something wrong causing the alternator to overheat. Just that it seems unlikely without other symptoms.
What is the alternator rated for?
Correct, I worded that oddly. I meant disconnect the battery when your wiring up the ammeter as that wire is live 12v when the key is off... then hook it back up after everything is bolted together, taped up and ready to go
jacob dehart
Newbie
Alternator is a standard AC Delco remy, not the heavy duty. Rated for 145 amps. Not sure if i bought one re manufactured or new.
Using proper test equipment, I'd want to see within 10% of 145 amps at fast idle, full load.
Using shade-tree test equipment, I suppose anything over 80-ish amps is probably OK, provided there's almost no AC voltage at any point--loaded, or not loaded.
Using shade-tree test equipment, I suppose anything over 80-ish amps is probably OK, provided there's almost no AC voltage at any point--loaded, or not loaded.
It does help, Jacob!
First things first. Good on you for paying close attention to the operating temps of your alternator,
especially on a barely driven recently purchased vehicle where the electrical system was modified by the
PO who was long on confidence & short on talent. (!)
Anyway, it sounds like your usage patterns = a rational amount of power for your alternator to deliver, so
you *should* be in a good place. (See 1st attachment for an example of an enthusiast who had no choice
but to upgrade to an alternator that could dissipate the heat generated as a byproduct of his large, high
duty cycle electrical loads.)
So, instead of telling you to panic, or to ignore it, my suggestion would be to monitor it until you are sure
that it's thermal behavior matches it's workload. And what I mean by this, is that if the alternator stays
reasonably cool with little/no load (think fully charged battery, car idling, no other electrical loads on) ...but
warms up while supporting everything turned on -- but then reverts back to cool operation with the loads
turned off, then I would be alright with this.
Conversely, what I would NOT want to observe is an alternator that's supporting some constant nominal load
(say 25 amps total) and sometimes the alternator is cool, but other times heats way up. Erratic operating
temps while working into a constant load is bad juju. We could have a thermal-intermittent voltage regulator
or one or more diodes that are starting to break down. In the land of electronics, parts can be & often are
intemittant before they finally fail outright.
Of course, the human response to temperature changes is anything but linear. So in order to quantify the temps
you are observing, as others have mentioned you should really consider adding an IR thermometer to your tool
collection. (See 2nd attachment for an affordable example with mostly positive reviews.) If you have this, and are
seeing the 275-350° F readings that the Offshore dude mentioned in that 1st attachment, then yeah, I can
identify that as abnormal and we should investigate further.
But (for arguments sake) you are seeing 120°F with minimal load, and 160°F with everything on, the voltage
remains steady, the bearings are quiet, etc...then you should be good to go.
****
By the way, you expressed a fear of the possibility of hidden shorts causing undue electrical load? Well, IF the
wiring is still protected by the factory fusing, a short should make itself evident by blowing the associated fuse.
But the great thing about the fuse block is that YOU can easily take control of the power distribution for
troubleshooting purposes. Let's say that you had the good taste to install a decent ammeter, and you are
seeing a current draw that doesn't make sense to you? No problem. I'm going to start pulling fuses for all
the non-essential stuff first (power sunroof, power windows, electric doorlocks, rear window defroster, audio
amps, heater blower, CB radio with a big honkin' illegal linear, etc. :0) ...and when I pull the fuse feeding into a
(for example) jammed/stalled motor, then the amperage will immediately drop back to normal.
Seriously, the majority of the time if you are experiencing an excessive draw in the wiring harness, it's normally
enough to blow the fuse. (Assuming the PO didn't fill the fuse block with *wrong*/high amperage fuses!) On
the other hand, it's rare but possible to have something like a constantly-on lock solenoid or jammed motor
doing the slow bake while out of sight.
****
One of the reasons I responded to your initial message is that you specifically mentioned finding/fixing problems
with voltage readings. That told me that you were serious about this. People act like electricity is magic, or
beyond comprehension. It can be -- but only if you refuse to arm yourself with the proper test equipment.
I can't make basic checks without a voltmeter any more than I can tighten heads bolts by hand.
And a quality ammeter is like a quality torque wrench -- you don't need it everyday...but when you do, you
really do need it.
And an oscilloscope literally shows you everything. It is the tool where the only limits to what can be
observed/understood is the gonkulation limitation between the troubleshooter's ears. (I speak from
personal experience. :0)
****
Hope this is helpful. If nothing else, you realize that with enough test equipment we don't have to guess about
anything having to do with your electrical system. As I mentioned in the beginning, I'd like you to observe
the alternator's behavior carefully for any anomalous behavior until you are comfortable with what's going on.
And if you (like a lot of us would) want to use this situation to add an ammeter and IR thermometer to your tool box,
then by all means go for it.
Here's wishing you cool running...
Attachments
Last edited:
Similar threads
