Electrical fault

[Samp96]

I've left my roadster for a while went to start it and both the battery in the car and key was dead changed them both car started first time but have absolutely nothing on the electrical side working has anyone got any thoughts on what it could be

[dan944]

I've left my roadster for a while went to start it and both the battery in the car and key was dead changed them both car started first time but have absolutely nothing on the electrical side working has anyone got any thoughts on what it could be

Checked Fuses?

[Samp96]

I've checked the normal ones in the engine bay and under the bonnet but I've only checked the small ones up to 30amp don't no how to check the bigger ones

[Joesson]

My PFL 2002 has an immobiliser system (red)light that is constantly on. Just checked to be sure and my 2 hasn't been started since end of October, but the battery is on charge.

I've always believed, from experience, that a car battery will loose power over tiime and thought that this was just a thing with lead acid batteries. But I had a look on the www and there are several references as the following:

Faulty alternator diode. What can drain a car battery when its off? The alternator does the jobs of supplying power to a few electrical systems and recharging the battery. If its diode is corroded, it will cause the circuit to draw power even when the engine is not running.
Car from Japan .com


Whether similar applied when we had dynamos I don't knowbut that was when I had most problems with batteries.

[Samp96]

It's not a battery problem I put a new one in and the car started its everything else that doesn't work like the imoblizer and heating, windscreen wipers, there's just no power going to anything else

[Carolyn]

there are two connections to the positive battery terminal.  one does the starter motor, the other does the rest.

Worth checking both are well connected to the terminal.

[Joesson]

It's not a battery problem I put a new one in and the car started its everything else that doesn't work like the imoblizer and heating, windscreen wipers, there's just no power going to anything else

Sorry, my misunderstanding, but I see that Carolyn is on the case so you should soon be seeing the light/s.

[Samp96]

I checked both cables and they seem to be fine are they fused or anything

[jonbill]

Might be worth looking under the   passenger side storage bin for water and the control units and connectors.

[Carolyn]

I've been thinking about this one.

The car starts but NOTHING else works?  Really Nothing?  Headlights? windows? Indicators?

Some circuits must be ok for the ignition switch to work.

If you can tell us exactly what works/doesn't work, it would help.

[Samp96]

The only thing that works is headlights ive got no rear lights, windows, heating, clock, dials , power steering

[Carolyn]

Check the 100 amp fuse in the fusible link block.  the box next to the battery.

It's a big rectangular one nearest to you.  Pull it out and check for continuity.  Disconnect the battery first!

If that isn't it check the other big fuses.

If it's blown. replace it.  The worry is: why did it blow?   If the replacement blows, the alternator has a short.

[Samp96]

How do you check the bigger ones

[Carolyn]

It's a bugger.  Disconnect the battery and remove it, disconnect the big wire that goes to the top right corner of the fuse box.

Then unbolt the fuse box from the car.

There are plastic tabs around the sides of the fusebox that have to be un-clipped to open it up.

THEN you can get to the back of the fuse.  It's held in with a screw.  Remove the screw.  Remove the fuse.  Check with multimeter.

I've never done it on an MR2 but it looks the same basic set-up as other Toyotas.

https://www.spyderchat.com/forums/showthread.php?24334-Removing-amp-Replacing-The-100a-Fuse

EDIT: The tops of the big fuses are transparent, so you should be able to see if one is blown.

[Samp96]

I broke the fuse trying to get it out I've ordered a new one is there anything else I can check whilst I'm waiting for it to arrive

[Carolyn]

You could check the alternator for a ground fault.

Bit of a bugger to get to, but you need one probe on the terminal where the wire from the battery bolts on and one to the body of the alternator, or to any earth on the chassis.

It should be an open circuit if it's not faulty.

[Samp96]

Finally got round to installing that fuse today and it workerd everything is working again thanks

[Ardent]

Great news.
Just leaves Cs question though, why might it have blown. 

[jonbill]

Hooray