The instrument brake light dims a litlle bit when i take the brake off the car! It does it with the vehicle´s headlights lights on or off! What could be the cause of this and where should i check to get this sorted out! I have already connected and disconnected the turn signal switch for any loose connection but it has no effect. Any recommendations? The bulb is a red led bulb!

Edited November 23, 20159 yr by jalexquijano

Anytime the brake light comes on with the parking brake released is indicating a brake system failure. Underneath the master cylinder is a body with brake lines running through it. Your car has two brake systems. If more pressure is applied to one of those systems, it makes a contact to ground lighting the brake light. The light is dimmer because you have a dirty switch  or corrosion in the ground path.

 

If the brake systems are operating normally - and you can verify it -there is a high resistance short to ground somewhere. You can verify a brake system failure by unplugging the wire lead attached to the center of the body mentioned above. If the light goes out when you disconnect it, you definitely have a brake system failure that needs to be fixed.  

Edited November 23, 20159 yr by djwarner

Anytime the brake light comes on with the parking brake released is indicating a brake system failure. Underneath the master cylinder is a body with brake lines running through it. Your car has two brake systems. If more pressure is applied to one of those systems, it makes a contact to ground lighting the brake light. The light is dimmer because you have a dirty switch  or corrosion in the ground path.

 

If the brake systems are operating normally - and you can verify it -there is a high resistance short to ground somewhere. You can verify a brake system failure by unplugging the wire lead attached to the center of the body mentioned above. If the light goes out when you disconnect it, you definitely have a brake system failure that needs to be fixed.  

 

Can you point out directly where should i check or disconnect? I have taken some pictures of the master cylinder. Fluids seem right!

The photo on the left is the body I referred to. There are two steel pipes, one on each end and a wire connected to the center post. Simply pull off the wire to test the circuit.

okay! i followed your instructions remover the connector from the brake line. Got inside the car and the brake light is on when the e-brake is pulled. If released, the brake light dissapears completely. I decided to clean the connector with contact cleaner and brass wire brush then tightned the connector with a pair of pliers but after connecting it back and testing the e-brake light stills dims when the ebrake is off. What could be the cause of this?

Unfortunately, the unit is not repairable, but they were used for many years and should be available. Datsun called the body "Assembly - Switch Brake Indicator".

 

The parts manual lists two part numbers, 46100-26100 and 46100-U5200. The last number superseded the older 46100-26100, but either one should work.

 

The light is dim indicating deterioration internally. If there was an external brake system failure, the light would go out when brake pedal pressure is released 

Well i think i can live with it! Unless i can find a replacement! Thanks for you kind advice! I guess many owners could have the same problem!

Edited November 24, 20159 yr by jalexquijano

Unfortunately, the unit is not repairable, but they were used for many years and should be available. Datsun called the body "Assembly - Switch Brake Indicator".

 

The parts manual lists two part numbers, 46100-26100 and 46100-U5200. The last number superseded the older 46100-26100, but either one should work.

 

The light is dim indicating deterioration internally. If there was an external brake system failure, the light would go out when brake pedal pressure is released 

I cleaned the female bullet connector and the male in the assembly switch, plugged it back again, got inside the car and reléase the emergency brake. The result was the same, the red brake line in the speedometer showed up very dim as in the picture. If i unplug the female bullet connector and reléase the emergency brake, the light is completely gone. I do not think it is a corroded contact on the e-brake switch. WIth these facts do you still confirm it is an internal problem of the assembly swith blade indicator???

Corrosion makes a high resistance or open circuit. The fact that the light comes on at all indicates there is a current path to chassis ground. The fact that it is dim indicates a high resistance path to ground.

 

If corrosion existed at the bullet joint, and if it affected performance of the circuit, removing the corrosion would only may the brake light glow brighter. But the brake light would still indicate a brake system failure.

No other posible way of cleaning this assembly?? Its getting hard to find one!

Strangely the problem dissapear and the light went out completely after a hard acceleration at the highway!

If it stays off after moderate braking, drive it til it recurs.