Brake light on and off (1 Viewer)

[caladin]

My brake light started to turn on for a bit (5 min?) then go off during the drive tonight.

Was 3/16" low, topped it off.

Continued doing it.

Other than a wiring issue & plug issue, can anything else cause it?

Seemed to come on when I hit bumps, making me lean towards wiring, but I figured I'd get advice if anyone had it.

Thanks,

E-

 

[OSS]

The parking brake handle also has a switch under it that triggers the red brake warning indicator on the dash when the handle is pulled.
Maybe check out that switch. Remove the fabric brake lever cover and see what’s going on.

 

[David*BJ70]

Here's what can trigger a light braking warning.

 

[Michael Hanson]

Hi, Is the small rubber pad in good shape behind the pedal. Some are missing some are there but have holes in them no longer keeping the switch off.

 

[caladin]

Thanks Everyone!

 

[2mbb]

Hi, Is the small rubber pad in good shape behind the pedal. Some are missing some are there but have holes in them no longer keeping the switch off.

This switch and pad effect when the brake lights in the taillight assembly turn on and off. I think the OP is having a problem with the brake warning light on the dashboard.

 

[Michael Hanson]

Then I would look for low brake fluid or a bad brake fluid reservoir top sending unit.

 

[2mbb]

Here's what can trigger a light braking warning.

View attachment 3162697

I'm not sure if the US FJ60 has the vacuum switch. I see some trouble shooting procedures in the 1984-1990 Chassis and Body manual, but the wiring diagram in that same document doesn't show the switch. I don't think I have the vacuum switch on my 1985 FJ60. I also looked at a 1980 Body and Chassis manual I have. The vacuum switch is not shown for the FJ60 but is shown for the BJ- andHJ60. I think the diesel engines also have separate vacuum pumps.

 

[David*BJ70]

@2mbb, you are probably right.

My diagram provided is for the 3B and 2H motors. This is a clumsiness on my part. I have studied the diagram so many times but obviously never paid attention to the fact that the combinason meter (diesel / gasoline) is not located at the same place (on the diagram).

Also, indeed, the vacuum pumps of the B and H series engines are behind the alternator.

... Therefore, the brake light will only be associated with the oil level in the reservoir or the handbrake. The 1980 manual for FJ60 is very clear on this point.

There is however a vacuum switch on the 2F motors but I don't know what would "happen" if it detects a malfunction. How could the driver knows

 

[2mbb]

@2mbb, you are probably right.

My diagram provided is for the 3B and 2H motors. This is a clumsiness on my part. I have studied the diagram so many times but obviously never paid attention to the fact that the combinason meter (diesel / gasoline) is not located at the same place (on the diagram).

Also, indeed, the vacuum pumps of the B and H series engines are behind the alternator. That said, I'm curious as to why there would not be a vaccum switch on the gasoline engines as there is a necessary need for vaccuum for the operation of the brake booster or possibly the clutch booster.

Thanks for the clarification. I see the schematic you showed now on another page of my wiring diagram.

on gasoline engines the booster gets vacuum from the intake manifold. Intake manifold vacuum is highest when the engine is running but the throttle plate is closed, as when idling, but also when decellerating which are both times when the brake might be applied. This doesn't necessarily negate the need for a warning light if the vacuum isn't there, or there is a leak elsewhere in the system. I'm no expert, but I have never come across a gasoline engine application with such a warning switch--at least not in the US.

 

[David*BJ70]

@2mbb I edited my post while you quoted it.

The pics (post #9) have been pulled from page 839 of this manual (page 839 in «my» PDF document of the FSM)

Picture on post #3 is from this FSM

 

[2mbb]

@David*BJ70 : This is an interesting conversation, but I hope it's not too off topic. I also looked at the parts diagram and saw the vacuum swith for the 2F. The vacuum switch connected to the emissions computer is used to control the Fuel cut solenoid on the gasoline engines (2F). It senses the vacuum in the throat of the carburetor near the throttle plate. It is not technically measuring the same vacuum source used for the brake booster. The switch below seems to have similar specifications to the one used in the diesel applications for the brake warning light but the part numbers are different

 

[atlshaun]

I was having a similar issue and my fluid was slightly low. Topped it off and the issue remained.

I pulled the cap off my brake fluid reservoir and manually moved the “float” and the light turned off. It was slightly sticky so I moved it back and forth a few times and now it works fine.