I have to put in a broadtail or Move it around every time to start the car

KRISTIFRISK

MEMBER
1990 TOYOTA CAMRY
4 CYL
2WD
AUTOMATIC
147,000 MILES

Hi Guys. :)
I have to put in a bradnail or move it around every time to start the car (see pic 1). This fuse was missing when we bought the car and my son noticed this little box spliced into the positive battery cable with 3 fuse compartments. The middle fuse was missing and a small copper wire was bridging the gap between two copper flat pieces. The reason he was looking, is because we were having to get jumps everywhere we went because the car wouldn't start. My questions are:

1. What is this fuse called, part number and what is its purpose and why is it so necessary to cause the car not even be able to start?

2. If I replace it with the original fuse will that fix it or will it continue to blow like it does now I think because I have to move the bent brad nail around every time I try to start it again?

3. If it continues to blow, what process do I use to try to troubleshoot and fix it?

This is my only car and I live 20 miles to the nearest Walmart for my food and groceries. None of my windows, radio, ac blower work (don't know where A/C blower fan fuse is, it worked the last time I got car started then turned on A/C button and it blew the blower fan out!). I don't know where to start. Can you help? Thanks so much for trying. Must be hard to do from a distance.
Kristi

5 Replies

KRISTIFRISK

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4 POSTS

Here are the pictures. Thanks!

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Thursday, February 25th, 2021 AT 4:17 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

Good evening,

The fact the fuses were missing means that the seller knew there was a issue and made it your problem.

https://www.2carpros.com/articles/how-a-car-fuse-works

https://www.2carpros.com/articles/how-a-car-fuse-works

https://www.2carpros.com/articles/how-to-check-wiring

You have to find the reason for the main fuse failure. Something is causing the fuse to fail. In most cases, it is the alternator that causes this issue.

I attached some diagrams for you to view. I would start by disconnecting the alternator and see if the fuse still fails.

Roy

INSPECT CHARGING CIRCUIT WITHOUT LOAD

NOTE: If a battery/alternator tester is available, connect the tester to the charging circuit as per manufacturer's instructions.

(a)If a tester is not available, connect a voltmeter and ammeter to the charging circuit as follows:
a. Disconnect wire from terminal B of alternator, then connect ammeter negative probe to the wire.
b. Connect ammeter positive probe to B terminal of alternator.
c. Connect voltmeter positive probe to B terminal and the negative probe to ground.

imageOpen In New TabZoom/Print

(b)Check the charging circuit as follows:
With the engine running from idling to 2,000 rpm, check the reading on the ammeter and voltmeter
Standard amperage: 10 A or less
Standard voltage: 13.9 - 15.1 V at 25°C (77°F) 13.5 - 14.3 V at 115°C (239°F)
If the voltmeter reading is greater than standard voltage, replace the IC regulator.

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If the voltmeter reading is less than standard voltage, check the IC regulator and alternator as follows:
With terminal F grounded, start the engine and check the voltmeter reading of terminal B+.

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Thursday, February 25th, 2021 AT 4:17 PM

KRISTIFRISK

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4 POSTS

Hi Roy,

Thanks! I see from the pictures that this fuse is labeled 80A Alt(thanks for the red circles lol) Yea, Previous owner knew about it, had to.

How do I know I am blowing a 80A fuse if I don't have a fuse in it? When power flows through that little brad nail would it be powerful enough to move the nail off center causing me to have to wedge it in again to start the car?

What is the purpose of this fuse? Which way does current flow? Does this fuse send battery power to the Alternator or does this fuse transfer amps to the battery?

Do you have the complete wiring diagram?

Lastly, in the main fuse/relay box under hood(not on positive battery cable), there is a relay labeled "Main Engine"(I think you called the 80A Alt fuse "Main"(I was confused)? What does this relay "Main" do and does it have anything to do with the 80A Alt fuse. I don't have the electrical knowledge to do what your saying to do about all the testing. Looking for a work-around. You said to disconnect the alternator from the battery and see if the 80A Alt fuse blows, firstly, I don;t have the fuse only the brad nail. Secondly, even if I had a fuse in there, would the car start(thought the alternator had a wire going to ignition?).

Thanks for all your help.

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Thursday, February 25th, 2021 AT 4:17 PM

KRISTIFRISK

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4 POSTS

What causes the 80A Alt fuse to blow? Excessive amperage coming from alternator to battery? That would mean the amps on this circuit are flowing from the alternator to the battery and the fuse blows to stop excessive amperage from overcharging the battery, is that right? If that is right, then the alternator isn't charging the battery when running necessitating having to get a jump and the battery being drawn down.

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Thursday, February 25th, 2021 AT 4:17 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

The alternator itself may be shorted out internally.

Remove the battery wire at the back of the alternator and then install the fuse and see if it fails.

Roy