10 Amp Engine fuse on an 89 FI

[dalebwilson]

Remove all temporary wiring. Disconnect the 3 alternator wires, white, red, brown. Put a new 10A fuse in under the dash Make sure your battery has a good charge. Start the engine and see if the engine will stay running.


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[gunnerw]

Ok, I did as you said, disconnected the alternator and replaced the fuse. The car started and ran for 5 minutes

[dalebwilson]

Did the fuse blow again?


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[gunnerw]

No. I shut it off after 5 mins. It then cranked right back up.

[dalebwilson]

Ok. Your alternator may be overcharging or have a short circuit. Take your alternator to your local parts store and have it tested. In the interim, re-connect the 3 alternator wires one at a time and crank the engine after each. This could point to which circuit is faulting.


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[gunnerw]

I took the alternator to AutoZone and had a friend test it on their machine. It passed all 4 tests. Here is the results.image.jpg

[dalebwilson]

Ok. Re-Connect the alternator wires one at a time and crank after each.

[gunnerw]

OK, reconnected the white wire and it ran fine. I removed the white wire the reconnected the "T" connector with the red/blk and wht/blk wires and it ran fine. As soon as I reconnected all three it started and 10 sec later it died. Do I need to make wires to test the the red/blk and wht/blk separately?

[dalebwilson]

I would do that to help you narrow down the short circuit. One circuit is the headlight and the other is the meter circuit with the charge lamp in the instrument panel.


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[gunnerw]

Funny say headlight because the left headlight is burnt on the inside

[dalebwilson]

Yes. You definitely have a direct short circuit coming off your alternator that is blowing your engine fuse. You may have found your problem.


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[dalebwilson]

Try pulling the HEAD fusible link and see if the engine stays running.


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[tooldude]

Like dalebwilson is saying ^. I don't have a specification for Festiva, but a typical alternator of its type should not have more than 0.5V AC ripple. Yours is more than double that and rises extremely fast from near 0 (it is there) to 8.1% of the DC. Regulated voltage is over the FM spec of 14.4V to 15V and the alternator being in-circuit blows the engine fuse. It sure seems like an internal problem with the alternator. There is no direct short to ground or the fuse would blow instantly. There is resistance in the circuit and the fuse is blowing relatively slowly because either there is an over-voltage or a resistance has been altered (lowered).

[gunnerw]

Ok I have disconnected all three wires leading to the alternator. I have then reconnect each wire alone to the alternator. With each wire the car crank and runs. I also removed the Head Fusible link (which I replaced all fusible links with large box fuses as pictured) as the car was running and it had no affect the car kept running.

I am wondering at this point if the alternator is the problem. When the 10a fuse does blows its never instant its always a slow bloeimage.jpg

[dalebwilson]

Your fusible links could have been loose, weak or corroded causing issues. Try running and driving it for a while with the PAL fuses installed.