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Electrical problem

I took the alternator off our 1998 Huyundai Elantra yesterday. The battery was going dead. I too the batter out too. I had them both tested at Autozone and the alternator tested out fine but the battery showed as bad. I bought a new battery and put it and the alternator in. Everything worked fine until this afternoon I was driving down the road and noticed the digital clock getting dimmer. Then it stopped working. Then the radio shut off. Then the airbag light came on. It never lost so much power it would die ( i.e. quit powering the fuel pump). What’s the deal? Any ideas? Was the test on the alternaotr false?


Have the alternator checked again. From what you describe, it sounds like the alternator isn’t charging the battery. When this happens, you run vehicle off the battery until it gets drained to the point where electrical systems start dropping out and the vehicle shuts off.


Also look for the simple solution: make sure you hooked the connections up to the alternator properly (and that there are no broken wires inside the rubber connector boot, if you have one).

I’d think that if the alt were not charging the battery, then the warning light would come on. However, there are probably some failure modes where the light does not come on. Does the warning light come on in the car’s self-test mode, when you turn on the ignition before you start the engine?

re check the wires to and from the alternator. also the wires to and from the battery. also follow the wires where they go to the other ends.

if you see any corrosion or green flakey stuff clean the connections and retighten them. it sounds like you have loose connections somewhere so the alternator can get the juice TO the battery to charge it.

on the far side, you may have a broken wire in the wires from the alternator to the battery too.

Bad ground or primary positive electrical cable. The cables corrode internally. Run a brand new ground cable from the engine block to the negative side of the battery (make sure the connections are clean and tight; prepare by wire brushing). Costs about $8. If that works, and I suspect it will, run a second ground cable body to battery, and replace the primary positive leads.

Also, a common mode of alternator failure is the (forgive me if this gets too technical) “it’ll work for a while when you whack it with a wrench” type. In the process of you taking the alternator off and the guy at the parts store plunking it down onto the test bench, it may have gotten a little jostle that made it work for a while. Hence the supposed “good” result. Try checking the battery voltage at rest and then with the engine-- the voltage with the engine running should be a few volts higher than at rest. If not, then either the alternator is bad or not hooked up properly.

The factory wiring diagram for my 02 Sonata shows me that there are two fuses in the charging circuit.

If your Elantra is wired the same & if the idiot light on the dash works, you only need to check one of these fuses.

One MAJOR advantage that Hyundai owners have is that they can signup for a free account at & have online access to the same factory shop manual & electrical troubleshooting manual/wiring diagrams that the dealer mechanics use.

Since my “internet browser” does’nt work at the Hyundai site, I picked up the paper back version of the manuals at my Hyundai dealer for 25 bucks each.

Talk about a bargain.

Sign up at the hyundai site and pull up the wiring diagrams…