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Renix-era brake light spookiness

cumorglas

NAXJA Forum User
NAXJA Member
Location
western new york
I have an 89 4.0/aw4/242, no ABS. it has lately started showing the red light on the dash that says brake sometimes. by sometimes i mean sometimes it comes on sometimes it goes off.
the jeep stops fine. fluid is at the same level it was when i replaced pads 4k mi ago. no wheel cyl or caliper leaking. ebrake not on. and ebrake switch seem to be working properly when tested with DMM. i will be honest here and say that the ebrake gets used only a couple times year( inspection and maybe once or twice to make sure the cables haven't seized)

it doesn't appear to have any relation to anything else. ie not on/off with braking. sometimes hot sometimes cold. sometimes at idle in park sometimes at highway speeds.

i'm stumped.




what else am i not thinking of that can cause that light to go on. maybe a bad sensor?
 
YEa my 88 has that light if it is the same one? Only comes on when the ebrake is pulled. The actual mechanical part of the ebrake light switch could be getting worn out. Try to get a pic of it or be more specfic on the location of the light in that light display.
 
A bad combination valve could also cause the light on the dash to come on. Try disconnecting the lead at the combination valve and see if the light goes out.
 
The fluid level sensor in the resovoir can cause this light to come on. Sometimes my "float" will stick in a low fluid level position. Check to see the level of the float the next it comes on.
 
1985xjlaredo said:
Try to get a pic of it or be more specfic on the location of the light in that light display.
all the way to top all the way left. above 4wd part time full time indicator.
 
Like stated above, two things turn on that light. One is the parking brake lever, and the other is the switch built into the combination valve.
Turn on your ignition key with your parking brake off, and foot off brake pedal; you should not have a brake light lit.
Pull up on the parking brake lever. The light should go on.

The switch on the combination valve is only actuated if either the front or rear hydraulic brake circuit has a massive failure, allowing the piston inside the combination valve to move.
If the parking brake lever turns the light on and off as you cycle the lever, which is correct, try pulling the connector loose from the combination valve, as already suggested, and see if the light stays on. If it does, the the combo valve is shot. If the light stays on, there's a short in on of the two ciurcuits.
 
Try reseting the switch on the combination valve. Disconnect the wires, unscrew the switch, screw it back in and reconnect the wires. Had this problem on my 88 after bleeding the brakes.
 
xjbubba said:
Like stated above, two things turn on that light. One is the parking brake lever, and the other is the switch built into the combination valve.
Turn on your ignition key with your parking brake off, and foot off brake pedal; you should not have a brake light lit.
Pull up on the parking brake lever. The light should go on.

The switch on the combination valve is only actuated if either the front or rear hydraulic brake circuit has a massive failure, allowing the piston inside the combination valve to move.
If the parking brake lever turns the light on and off as you cycle the lever, which is correct, try pulling the connector loose from the combination valve, as already suggested, and see if the light stays on. If it does, the the combo valve is shot. If the light stays on, there's a short in on of the two circuits.

An edit to my previous post. Change the underlined portion above to read:
--"if it doesn't, the valve is probably fine."
 
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