Alternator Bench Testing and replacement

[720_Jeff]

Truck has been dying on me recently.  Tested at the battery, truck idling only getting 12.2v there. 

 

Had an old alternator, tried getting it tested.  Went to O'Reilly, they couldn't find the right adapter.  Off to Car Quest, no bench tester, Pep Boys now their parts is Advanced Auto, again, can't find the adapter.  AutoZone, they have the adapter, but bench tester doesn't work.  Nice girl calls next store over, they say they can test it.  Go there, they tell me their machine is broken.  I ask for the guy by name, he says, sure he can test it.  Weird?

 

He looks up the alternator, finds the adapter code and part number.  Turns out, @ AutoZone, probably others, the 720 is listed under Truck and cars, as I came to understand.  The car part number is wrong, different connector at the back of the alternator.  Truck, has the T looking receptacle.  With that, he was able to input the correct part number and got it tested.  Turned out bad.  

 

It has the Hitachi logo in the casting, so I'll keep it and rebuild, but since we are down to one car, well I must buy one and put it in, however long it lasts.

 

Lesson is, if the parts person can't find the right looking adapter for their bench tester, have them try the part number under Truck instead.

[Stoffregen Motorsports]

What are you talking about? The book is never wrong.

[720_Jeff]

And always trust the parts counter guy.  He said, 12.2v, that alternator is fine.  He question was, what are you running, as in stereo/etc.  Told him, only the engine and occasionally the headlights

 

[]2eDeYe]

12.2 volts is less than a fully charged battery. Bad parts guy, no treat. 

[banzai510(hainz)]

I would check the fuses in case usually the ignition fuse but if you get a ign light then its ok

 

buy this or a version of this they work great let you monitor while driving with lights other loads and one can see if the alt gets weak in certain situations.  this will catch it way before the ignition light come on and your stranded(running on the battery)

https://www.ebay.com/itm/233055344476?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3D88cf91e9699f4cbb861a642f56a131fc%26pid%3D101224%26rk%3D3%26rkt%3D5%26sd%3D155065702267%26itm%3D233055344476%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1

Edited August 3, 2022 by banzai510(hainz)

[720_Jeff]

Now, interestingly enough, I have two remanufactured alternators.  Cases look 100% new, in fact they don't have any logo's in the casting.  Pretty sure, the originals would have a Hitachi logo.  If not, then a Nissan logo?

As far as I can tell, insides are clean as a whistle, honestly, appears to be 100% new?

 

If you all want your alternator bench tested, might be handy to have a Hitachi T to SL adapter in your back pocket, just in case.  Currently, easily found on eBay.

 

 

[banzai510(hainz)]

using the cheap volt meter I mentioned above is the best thing around. You dont have to pull the alternator out.

 

You load test by putting your heat and lights on and can see immediatly if the alt is weak.

 

as for the alt with not Hitachi or Mitshibishi making on the case. there are alot of chinese clones coming on the market.

even if the case is marked Hitachi these have been rebuilt a few times over the years and be honest I only get about 8-12months on these rebuild from Vatozone or O rileys.. This is a daily driver about 12k miles a year.

I got a WAI chinese build which are brand NEW made I got 3 yrs out of it so about 30k miles. they about 90$.   Im on my 2nd one but since I only drive my 521now maybe in summer it should last longer. 10yrs

 

The new alt in the later cars like the GM alts and others  last so much longer.  but in these truck the fitment is tight.

 

Edited August 4, 2022 by banzai510(hainz)

[720_Jeff]

I have the one you linked to, on order.  Looks like this might be something I'll have to deal with 😞

 

[Stoffregen Motorsports]

You could always swap to a modern mini alternator. Enough info out there to get it done. Custom brackets are the main issue. With the right alternator, you can ditch the external voltage regulator.

[720_Jeff]

At least 84-86 720's have internal VR's, I know mine does.

 

I could consider an upgrade.  Think I recall some talking about Altima and or Quest?

[bottomwatcher]

No special "T" connector need. Alternator has standard male spade connectors on it. I put female spade connectors on my wires and if I have to swap alternators in a parking lot I don't worry about having the right plug. A lot of newer alternators are ECM controlled. I just went through an alternator replacement on my duramax. I don't trust any parts store rebuilds and the factory new are expensive. Luckily I have a good starter and alternator guy nearby that works out of his barn. I can watch him rebuild and it is fascinating to watch. An old Hitachi is easy to rebuild but the newer alternators need a lot of special tools and some soldering I will stick with old school for the datsun.