voltage questions

Topic: voltage questions (Read 1195 times) previous topic - next topic

voltage questions

December 04, 2010, 09:39:20 PM

hi guys
i think i have some voltage issues but not sure. when i start the car it reads about 14.40 then levels to about 14.04 but sometimes it will go to 13. 60 or a little less. sometimes even runs 12.50 . i had the alternator load tested and its good. also put in a new regulator. the battery is good and fully charged. battery posts are scrubbed clean and all the wires are good and fully connected. grounds are good too.
this all happens with the headlights on and the heat running at high.
could altenator test good and maybey one of the diodes is going?
thanks for any help
eddie

voltage questions

Reply #1 – December 04, 2010, 10:20:18 PM

That sounds normal to me, under such a load and alternators at idle put out at best 30-50 amps, if you rev the car up and it goes back to 14ish then the alternator is probably just fine.

voltage questions

Reply #2 – December 04, 2010, 10:42:10 PM

not a 2v spread,,doesnt look normal to me

have it retested but pay attention to how the test is done. most of the people doing testing just flip a couple switches quickly and load it then they are done.

have it load tested for a longer period of time to simulate a warm situation.

yes it is possible to have a partially bad alt and still have it appear to run good.

put your meter to AC volts and take some readings. without the diodes, the alt will put out AC instead of dc.

Report back some new numbers when you take readings with your heater blower motor off.

Again, retest the alt

voltage questions

Reply #3 – December 05, 2010, 12:43:18 AM

Has the alternator ever been replaced? There are two versions of the 1G rear terminal alternator, a 40 amp and a 60 amp. They look the same. When new they had a color stamp on them, orange for 40 amp and green for 60 amp. When they are reconditioned they get repainted so no color stamp.
Your car needs the 60 amp.
I had this problem years ago on my 84 T-Bird. Running one night in a snow storm with lights, heat blower, wipers and rear window defroster on the battery ran down.
I convinced the parts guy he sold me the wrong alternator.

voltage questions

Reply #4 – December 05, 2010, 12:59:52 AM

When I was having charging problems with my car, my battery kept going dead. I ended up swapping out the alt that tested good with one from my last car. That one stays between 13.6 and 13.8 at idle, and around 13.4 with all accessories and lights on. When I had a dead cell in the battery, it would drop to 12.5 at idle, but would still get to 13.5 or so with a rev.

voltage questions

Reply #5 – December 08, 2010, 10:45:55 PM

we found out one of the diodes is not good. i think im going to to get a 3g alternator from PA performance.this was a rebuilt ford alt, but its the second one in 2 years. the one in now has a green stamp and it says 65 amp. pa performance looks and sounds like a good place. i found the site from a link on eric's cool cats.