MX83 Dead Electrics

[AKSA]

Anyone here know much about the MX83 electrical system?

I've just replaced a defective battery, but managed to reverse connect it for a few seconds. A few amps flowed briefly, burned out the 'Dome' fuse (20A) which I've replaced.

However, although head and interior lights work fine, none of the dash lights up when you switch on the ignition, won't start, neither does electric seat or radio work. Get the impression there's another fuse someplace I can't see that's blown as well.

I've located and checked all fuses and circuit breakers, no problem I can find.

Any ideas? Car is useless as it is.... new battery, won't move! I've tried to find a decent wiring diagram, but nothing seems available on the net so far.

You sure feel a right goose when these things happen.....

Thanks in advance, I've also posted this on the Cressida forum.

Hugh

[lexsmaz]

I can't picture the wiring of a mx83, but you should have some main fuses very near to the main battery lead or even in a block form off the battery terminal, i would suggest you look for them, they also could have a fusible link attached to the + battery terminal which will probably still look ok externally but will be burn't out internally, you will need to use a test light or multi meter to probe the wiring for power outage ..

Rob ..

[AKSA]

Thanks Rob,

I will check it out right now, get back to you.

Much appreciated,

Hugh

[AKSA]

Rob,

You were 100% right, and we now have resolution!! Now to add to the body of knowledge here.

Problem is the alternator fusible link. Rated to 100A it's the central link in the box just behind the battery in the engine compartment. It is now fused to the copper spades, will take some effort to remove and replace it. However, bridged the terminals and all is well, car starts, all accessories work fine, and God is in his heaven.

I spoke to an auto elec. His advice:

1. Nine times out of ten reverse battery polarity destroys the alternator diodes through overcurrent.
2. The alternator fusible link is also ALWAYS destroyed.
3. If the ignition switch is OFF, the ECU is almost NEVER damaged.
4. Repair is straighforward and not expensive, particularly if you acquire and replace the alternator diodes yourself.

I'm now pulling the alternator, will dismantle and repair it.

Rob, thanks for your suggestions,

Cheers,

Hugh

[petergoudie]

You might find it is not fused to the copper spades. Some of the links are bolt in underneath and others are not. I found this on a corolla. I had to remove the box and undo two bolts underneath or to the side. The other ones I could lift out. I guess they want good contact for 100 amp.

[AKSA]

RESOLVED!!

Turned out:
1. 100A fusible link gone, replaced.
2. Diode pack and alternator both tested good, no damage.
3. With new battery properly connected, drives like new!

So, the alternator diodes normally go in these situations, but they didn't in this case, link went first. Those diodes are TOUGH, and 18 years old, remarkable!

The wiring system on Cressys is very, very good, well designed and TOUGH.

Thanks guys for your help,

Hugh