10 Amp Engine fuse on an 89 FI

[tooldude]

That one particular part of the circuitry doesn't go through the 10A fuse. I can't get the pictures to post into this box. I need to instructions on how to do that. Someone send me an email address and post these pictures for us please.

[dalebwilson]

Check your inbox

[tooldude]

Check your inbox

I tried sending pics when I got back home, hope they work out.

[dalebwilson]

There were no attachments on the email.

[tooldude]

Strange, I sent a worded email which you got and 4 separate pics you didn't. I'll try once more, if that won't work, I'd have to mail copies, if the interest on this even holds out. Funny, not a peep out of gunner. Maybe he stuck a relay on already and headed down the road.

[dalebwilson]

[nitrofarm]

Strange, I sent a worded email which you got and 4 separate pics you didn't. I'll try once more, if that won't work, I'd have to mail copies, if the interest on this even holds out. Funny, not a peep out of gunner. Maybe he stuck a relay on already and headed down the road.

Maybe he took it to a a shop. But maybe he's just busy?

[nitrofarm]

Soooo after looking at these while laying sideways It looks like the only other thing that 10 amp is protecting, compared to the Later models is the Field Winding? I would look real close at that BK/W wire at the Alt plug. Its either the "Run" Coil in the F/P Relay or that BK/W wire to Alt. The car starts so its not the "Start" Coil in the F/P Relay. My First step would be disconnect that Alt harness & do the "Fuel Pump Test". If it passes that will eliminate the Run Coil & the Main Relay. Then only thing left is the Alt harness,what do you guys think? Thanks for posting the pics Tool & Dale ! Nitro-

[tooldude]

Just shows we Festiva types are a determined bunch, dedicated to finding out what's causing all that aggravation and will do whatever it takes, even if we have to get a picture in edgewise, right Nitro? Sorry you had to read that sideways, but at least you know you can still do it. Heck, that might come in handy under the car.

[dalebwilson]

1st drawing rotated right side up

[nitrofarm]

^ LOL Thanks,appears the OP is MIA.......

[tooldude]

Good question Nitro - what can we think? I've been trying to figure how to analyze this with little to go on. It began as looking like a bad alternator, as removing it from the circuit appeared to stop the fuse blowing. That can be misleading as unloading a circuit with a good part could remove enough amps to hide the true problem. That was looking at things superficially, but it seemed probable as the Alt seemed to have improper specs. What's needed is actual measurements and specifications. We can test current flow through those 2 relay coils & if excessive enough we would know the relay is bad. If we know its resistance we can accomplish this easier with a voltage drop and be sure about what any measurement means. A relay coil can't have 0 resistance and operate as no magnetic field would be generated. So what percentage of the coils can be shorted and still have function? As tolerances go, could one drop 20%-30% of its resistance and function? IDK the specs but most of these little coils are 40-60 ohms at 225ma-350ma. Losing over 50% of resistance to 20 ohms makes 680ma and that will not blow that fuse. I was looking at them superficially. If we get a 3 ohm resistance in circuit there will be about 4.5A current. So how much amperage is in that circuit?- good question. Looking at a time-current chart from Littlefuse gives some idea. These are approximate, but reasonably close, over-current specs for a 10A fuse: 40% blows around 300 sec/ 44.5% in 100 sec/ 46.2% in 60 sec/ 51% in 20 sec. Sounds like what gunnerw was saying.10A fuse makes an easy calculation of about 4 extra amps, 14A blowing the fuse - if correct, not a relay. That leaves the other possibilities of something connecting into the B/W wire or a "new" alternator bad right out of the box. I've had that happen. Funny, the spec for Alt field coils is 3- 6 ohms. What do you think?

[gunnerw]

Ok everyone. I found another main relay on Ebay. Put it in and that seems to have been the problem. Bad main relay. Thanks for everyones help. Now to continue... Next, new value cover gasket, exhaust and windshield.

Thanks again everyone

[nitrofarm]

AWESOME!

[dalebwilson]

Hip Hip Hurray!


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