How hot should an alternator get?

Both of mine are smoking hot - ie, I've got a burn chunk of skin missing the size of a quarter on my wrist by accidentally touching it.

I'm worried I've got wires hooked up backwards.....

Any thoughts?

Depends on the kind of alternator, I learned ALOT about alternators this spring that I NEVER new even after years of building cars/boats/hot rods etc. I doubt you have any wires backwards or batterys would go dead/blow up, burn wires off etc. We built a efi 1974 Transam, used a 10si 140 amp powermaster altenator because it has about 60 or so amps off draw and a optima red top battery, alternator would get to about 275 to 350 degrees when everything was running and then quit working. Had it waaranteed, same thing happened, put snap on amp clamp on and car drew between 40 to 80 amps, even more if you ran fans with car off, 10si is like a old gm alternator from 70s. It had a external fan, they can rate it at anything they want but only having a external fan it could/would NEVER support the amperage it was rated for, not even half, for very long without cooking. years ago I upgraded my alternator on my Baja to some 100+ amp one, boat had all kinds of electrical draw and is about 12years old. Took a hard look at it and see it has a external fan AND a built in internal fan, after cooking 3 alternators and incessantly pissing around with this car going dead everywehere I switched to a cs 130 style which has a external AND internal fan, havent had a single problem since then. Also keep a few things in mind, creating wattage/making aperage creates heat, their is a direct correlation, the more load there is the more heat it puts out. In my case optima red top, I read ALOT about these baterrys that I also didnt know, IF they get run down, unlike a lead acid cell batttery they will draw what ever the max output of your charging system is until pretty much fully charged, so in my case when we ran fans on car at chassis dyno it lowered the surface voltage, when we started it the alternator was maxed out at 100% for quite a while, and burned up on way home, people in the know say to ALWAYS top off optima batterys if they get run down with a charger NOT your charging sytem. In your case has anything changed from before, extra load on charging system? Has alternator actually failed and quit charging? If not I would probably just stay away from it to not get burned and leave well enough alone, Smitty

poor connections and or loose connections and even at the battery side and back side engine grounds can make the alternator run hot.

Improper not big enough sized battery cables

also weak batteries - 12.7 is a fully charged battery (engine not running)

also corrosion on any of the terminals including battery cable terminals.

All OEM marine engines including outboards do not want wing nut connections at the battery. NONE - they all recommend against wing nuts.

well is it charging?13v or higher

Yes, they are charging. All connections should be clean, the alternators are brand new and I just got the motors back in mid-summer so they haven't had time to corrode.

http://www.ebay.com/itm/NEW-ALTERNAT...item257eaf481e

This is the one I used.....

The batteries did go down because I left the stereo on for 2 weeks. I still wouldn't have thought they would have gotten that hot?

When they are putting out higher amps, they will get hot enough to burn you, up to 200F or so. The closer you are to the rating of the alternator, the hotter they get. The cheap alternator get hotter IME- they are generally pushing the compon ents to the edge.

As pointed out above, any loose or weak components strain the alt and make it heat more.

All good points above. But the ONLY thing that will get an alternator hot is LOAD. Most likely cause is low batteries. Especially multiple HD batteries like we all like to use. Try to consider a battery like a gas tank, a high capacity battery hold lots of power like a big gas tank holds lots of gas. The more power (gas) you take out the more power (gas) you have to put back in to fill it up. It can take a long time for the alternators to charge up your batteries.The units you purchased look like stock 65 amp units. They really don't make enough power to burn themselves out quickly, but you are definitely shortening their life by running them that hot. High output alternators would get even hotter, and may not last as long as the lower amp ones.

Best practice is to charge batteries with a charger when batteries get dead or low.


Having said that, you probably don't have much to worry about short term.

Are you sure the heat is coming from the production of voltage and not friction from the belt. Is it aligned correctly. Just a thought

They get hot, no doubt. Switching the selector to a near dead battery you could fry bacon on them. Agree that the heat is based on the load, low amperage draw they will only be warm.

I'll give them another look over this weekend, and throw a laser temp check on them now that the batteries are fully charged and see what we get.