How hot should an alternator get?
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Pro
Joined: Sep 2011
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From: EVANSVILLE Wisconsin
How hot should an alternator get?
I have a new Powermaster alternator that was factory tested at 80 amps at idle and 107 at 'highway speed' so I'm assuming that's at ~2800 rpm. I have no load to speak of (no lights, instruments, etc yet) on the alternator at this point other than my dual Spal's which are wired directly to the output post on the alternator. Even with the fans turned off, the alternator get's really hot and it does so relatively quickly, within a few minutes of starting the car you can hardly touch it. Temp gun says 140 degrees... Is this too hot and if so any ideas why when there is so little load on it (my battery is new and tested out perfectly).
Thanks for any help!
Greg
Thanks for any help!
Greg
Drifting
Joined: Aug 2005
Posts: 1,443
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From: Wauconda IL
Mnnn.. That doesn't sound right.
If your battery is in good shape and you have no load and your wiring is all up to snuff, the alternator shouldn't be doing a whole lot.
If it's putting out 80 amps at idle with no load, you have a problem.
Alternators are load sensing and only provide charging when needed and if everything else is in perfect working order, they is no way in hell you should be putting out 80 amps at idle w/no load!
Even with the fans on and everything else running, you would rarely need 80 amps charging for any length of time.
Let me guess, is this one of those 'one wire' wonders?
If your battery is in good shape and you have no load and your wiring is all up to snuff, the alternator shouldn't be doing a whole lot.
If it's putting out 80 amps at idle with no load, you have a problem.
Alternators are load sensing and only provide charging when needed and if everything else is in perfect working order, they is no way in hell you should be putting out 80 amps at idle w/no load!
Even with the fans on and everything else running, you would rarely need 80 amps charging for any length of time.
Let me guess, is this one of those 'one wire' wonders?
Thread Starter
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From: EVANSVILLE Wisconsin
Thanks Ezobens, the 80 amp rating was on the test card that was included with the Alternator and I assume was done on PowerMasters 'Alternator Dyno' to test and rate it before leaving the factory. Unless there is something wrong with the alternator I doubt it's putting out anything close to that at idle in my car since there is no load. That would make it hard to explain the heat though right? How could one test to see how much output is being generated? I tested the voltage and it was at 14.8 at idle, not sure about amps though. Here's a pic of the set-up. The Yellow wires are to the fans and the Red is my charge wire which does not run directly to the battery, it ties into the forward harness.
Thanks,
Greg
Thanks,
Greg
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
Wires look a tad on the thin side for a 107 amp alternator IMO but that really shouldn't be your issue.
The only real way to check output would be with an ammeter-
It may make sense to take it down to your local parts store to see if they'll test it for you.
It should not be generating that kind of heat if it's not doing much charging so either there is a problem with regulation and it's producing output when it's not needed (voltage really won't tell you that) or there is some other internal defect.
If you have the original alternator (if it works?) you can try swapping it out just to see if the issue is wiring related in the car vs in the alternator.
If you wiring/battery is sound, the original alternator should not get hot.
The only real way to check output would be with an ammeter-
It may make sense to take it down to your local parts store to see if they'll test it for you.
It should not be generating that kind of heat if it's not doing much charging so either there is a problem with regulation and it's producing output when it's not needed (voltage really won't tell you that) or there is some other internal defect.
If you have the original alternator (if it works?) you can try swapping it out just to see if the issue is wiring related in the car vs in the alternator.
If you wiring/battery is sound, the original alternator should not get hot.
Thread Starter
Pro
Joined: Sep 2011
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From: EVANSVILLE Wisconsin
Wires look a tad on the thin side for a 107 amp alternator IMO but that really shouldn't be your issue.
The only real way to check output would be with an ammeter-
It may make sense to take it down to your local parts store to see if they'll test it for you.
It should not be generating that kind of heat if it's not doing much charging so either there is a problem with regulation and it's producing output when it's not needed (voltage really won't tell you that) or there is some other internal defect.
If you have the original alternator (if it works?) you can try swapping it out just to see if the issue is wiring related in the car vs in the alternator.
If you wiring/battery is sound, the original alternator should not get hot.
The only real way to check output would be with an ammeter-
It may make sense to take it down to your local parts store to see if they'll test it for you.
It should not be generating that kind of heat if it's not doing much charging so either there is a problem with regulation and it's producing output when it's not needed (voltage really won't tell you that) or there is some other internal defect.
If you have the original alternator (if it works?) you can try swapping it out just to see if the issue is wiring related in the car vs in the alternator.
If you wiring/battery is sound, the original alternator should not get hot.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
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From: Hinckley OH
The other thing I would question is if there is another draw on the alternator. You might try disconnecting the SPAL's and see if that solves the problem. I think you can also disconnect the wire to the harness as well. The reason I say that is that my stud fell out of a brand new alternator and when I managed a Bubba fix (temporary) the alternator still worked. If the alternator heats up with absolutely no load then you know the alternator is the problem.
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Team Owner
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From: altered state
St. Jude Donor '05
Had a new alt with a bad diode ?? in it got hot without the engine even on
I was told by an alt shop if you try to cram too much alt power into a given case size they can get very warm.
I was told by an alt shop if you try to cram too much alt power into a given case size they can get very warm.
Pro
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From: Karlsruhe (Germany)
Thread Starter
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From: EVANSVILLE Wisconsin
Thanks!
Le Mans Master
Joined: May 2007
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From: North tonawanda NY
This may or may not have something to do with your findings but...
Its a commonly known fact that the original style housings that our cars have do not reliably cool the higher amp guts that many aftermarket companies put in them... this is why they have such a short life compared to the original 50-75 amp models its also why GM redesigned the case to allow better cooling on OEM minuet amp units.
Those wires look like 12 gauge..... waaaay too small for 107 amps....(I see you have multiple wires going to various things so it may not be so bad but you need a thicker wire to go to the battery) those wires should be hot as well if there's a large draw going through them.
Its a commonly known fact that the original style housings that our cars have do not reliably cool the higher amp guts that many aftermarket companies put in them... this is why they have such a short life compared to the original 50-75 amp models its also why GM redesigned the case to allow better cooling on OEM minuet amp units.
Those wires look like 12 gauge..... waaaay too small for 107 amps....(I see you have multiple wires going to various things so it may not be so bad but you need a thicker wire to go to the battery) those wires should be hot as well if there's a large draw going through them.
Last edited by augiedoggy; Aug 24, 2013 at 11:10 AM.
Thread Starter
Pro
Joined: Sep 2011
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From: EVANSVILLE Wisconsin
This may or may not have something to do with your findings but...
Its a commonly known fact that the original style housings that our cars have do not reliably cool the higher amp guts that many aftermarket companies put in them... this is why they have such a short life compared to the original 50-75 amp models its also why GM redesigned the case to allow better cooling on OEM minuet amp units.
Those wires look like 12 gauge..... waaaay too small for 107 amps....(I see you have multiple wires going to various things so it may not be so bad but you need a thicker wire to go to the battery) those wires should be hot as well if there's a large draw going through them.
Its a commonly known fact that the original style housings that our cars have do not reliably cool the higher amp guts that many aftermarket companies put in them... this is why they have such a short life compared to the original 50-75 amp models its also why GM redesigned the case to allow better cooling on OEM minuet amp units.
Those wires look like 12 gauge..... waaaay too small for 107 amps....(I see you have multiple wires going to various things so it may not be so bad but you need a thicker wire to go to the battery) those wires should be hot as well if there's a large draw going through them.
Le Mans Master
Joined: May 2007
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From: North tonawanda NY
Thanks Augiedoggy. The yellow wires are the ones supplied with the Spal Dual fan kit, I guess I would assume then that they are engineered to be sufficient. The wires are very high quality and each one serves a single fan limiting the current draw somewhat vs a single wire running both. The Red wire runs straight back to the fuse panel per a stock layout and is actually a leftover piece from the Spal kit. I believe that wire is 12 ga so perhaps that needs to be heavier. I guess I figured it'd be sufficient as it's a short run of about 3 feet. The Spal wire is different than stock however, in that it is comprised of many very small strands vs. the stock wire being fewer heavy strands. Does the Spal wire then inherently have more resistance??
Btw 12 gauge wire is good for a Max of 41 amps Max! And a continuous duty more realistically around 23 amps. when you have longer lengths or splices and junctions its good for less.
Last edited by augiedoggy; Aug 24, 2013 at 12:04 PM.
Pro
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From: Karlsruhe (Germany)
The red main wire is connected to the big wire at the starter, like in almost every car.
So there is always voltage on it, and there is no fuse in it.
If you replace this wire to the starter with a thicker one, your ampere meter will show lower readings then the real values.
I am back on the 40amp original alternator (and have electric fans too) and it works just fine. It just puts out lower current at idle.
So there is always voltage on it, and there is no fuse in it.
If you replace this wire to the starter with a thicker one, your ampere meter will show lower readings then the real values.
I am back on the 40amp original alternator (and have electric fans too) and it works just fine. It just puts out lower current at idle.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
I have a new Powermaster alternator that was factory tested at 80 amps at idle and 107 at 'highway speed' so I'm assuming that's at ~2800 rpm. I have no load to speak of (no lights, instruments, etc yet) on the alternator at this point other than my dual Spal's which are wired directly to the output post on the alternator. Even with the fans turned off, the alternator get's really hot and it does so relatively quickly, within a few minutes of starting the car you can hardly touch it. Temp gun says 140 degrees... Is this too hot and if so any ideas why when there is so little load on it (my battery is new and tested out perfectly).
Thanks for any help!
Greg
Thanks for any help!
Greg
Thread Starter
Pro
Joined: Sep 2011
Posts: 613
Likes: 11
From: EVANSVILLE Wisconsin
The red main wire is connected to the big wire at the starter, like in almost every car.
So there is always voltage on it, and there is no fuse in it.
If you replace this wire to the starter with a thicker one, your ampere meter will show lower readings then the real values.
I am back on the 40amp original alternator (and have electric fans too) and it works just fine. It just puts out lower current at idle.
So there is always voltage on it, and there is no fuse in it.
If you replace this wire to the starter with a thicker one, your ampere meter will show lower readings then the real values.
I am back on the 40amp original alternator (and have electric fans too) and it works just fine. It just puts out lower current at idle.
140 sounds normal to me, not an issue, figger under hood temps to be not much lower than that, especially at speed.....on a hot day in the sun....the alt sucks underhood air, and so off the headers and through the radiator, and so say 50 amp draw at ~13.5 volts do the math.....thing is fine.....
Race Director
Joined: Apr 2007
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From: South Western Ontario
I don't know how much current is going out but I did unhook the two yellow fan wires and the Red wire and it stayed nice and cool. I then hooked up the fans and started them up and it got hot fast. BTW, the Red wire is a hot wire regardless of IGN on / off. Is this correct??
Thanks!
Thanks!
No wires hooked up - cool?
Wires hooked up - cool?
Fans on - hot?
That sounds about right unless the above isn't correct?
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From: EVANSVILLE Wisconsin