Parking brake and ABS light on

[Unicyclist]

Hello, I'm new, and posted this in the new members forum before realizing that that was not the right one. I recently got my first car, a 1991, manual, 4x4 Explorer. A couple of days ago the ABS light and parking brake light came on and stayed on, stopping only for a couple of seconds right after starting. I have tried pulling up on the Ebrake to make sure it fully disengages. My understanding from reading other threads is that this can be caused by the switch the Ebrake contacts failing, or by the car sensing that the brake fluid is low. The light is still on when I disconnect the plug from the switch, so I think the car must be sensing that the brake fluid is low. It is not, the fluid is right at the full line.
Is there a stuck float in the little reservoir where you add brake fluid, or in the master cylinder? If so could someone tell me how to access it?
Is there anything else that triggers the parking brake light? The light stays on when I pull the plug off the switch that the ebrake hits, but brightens when I ground the plug. Is this indicating a ground somewhere?
Would disconnecting the battery to reset the computer make the lights go off if it was a glitch?
Thanks,
~Unicyclist

 

[Unicyclist]

Does anyone know how I can figure out if the problem is a short to ground in the wire to the switch on the brake? Is it probably safe to drive if I checked brake fluid level, and it was good, and emergency brake locks well when on, and disengages when off? the ABS probably won't work, but the regular brakes seem strong
Thanks, I just don't want to drive it if it could hurt the truck or is unsafe.

 

[wood1]

It's not going to hurt your truck unless your brakes fail and you run into something.

A logic probe is a worthwhile investment if you have an old truck.

I have disabled my ABS and the red brake light is not on. I have seen other vehicles switch that light on when the ABS is not working, effectively I pulled the fuse (put a switch in line). Not sure if the '91 is completely different, it only has RWABS and my '93 has 4WABS.

Is the reservoir level switch normally or open or normally closed?

 

[Unicyclist]

Thanks for your help. I am not sure about the reservoir switch. I tried to check in the reservoir, thinking the float might be stuck, but I can't see anything through the side, and there is a plastic filter thing under the cap so I can't tell. What is the difference between a logic probe and a test lamp?
Thanks, unicyclist

 

[wood1]

Logic probe plugs into the cigar lighter (or hooks to both positive and negative of the battery) and identifies a ground or positive voltage safely. It won't fry a computer, a test light isn't computer safe and can only tell you if you have a ground if it is hooked to power, and power if it is hooked to a ground. Also very much not computer friendly.

 

[Unicyclist]

Great, I'll get a logic probe. I have a Haynes manual on the way which should have the wiring diagrams, hopefully with that and a probe I can find the problem.
Thanks for helping me out with this
Unicyclist

 

[wood1]

I should have suggested you check the fuse first, that's easiest. The way you describe the lights coming on makes me think it is the ABS system causing the red light to come on.

This link is for 4WABS so I am not sure how much will apply to the RWABS. Good read either way. Maybe the codes can be read the same way?
http://www.explorerforum.com/forums/showthread.php?t=258803

This one seems like a complete schematic for the '91, might be of use to you.
http://www.scribd.com/doc/9719738/91-Explorer-Diagrams?in_collection=2307116

It's Larry's stuff (fixxxer). He has a bunch of diagrams etc here
http://www.scribd.com/user_document_collections/index/4599665

My Haynes manual is not much help. Suggests you check the fuses, connectors, and the harness to the rear diff. Not a bad idea mind you. Could be the connector to the module or the ABS motor under the hood has vibrated loose. Maybe the Harness to the rear diff is damaged?

If I had to guess on the level switch I would think it was a normally open switch but if it was the problem unplugging it would take care of the light so makes me think that it is not your problem. If it is indeed a normally closed switch then unplugging it and jumping the wires would verify that the level switch has failed.

I've never had a problem (other than it's crap) with my ABS so I don't know much about it really.

Good luck and welcome to the site!

 

[Unicyclist]

Sorry, I wasn't clear. The switch I was referring to is the one on parking brake, I haven't tried disconnecting the one on the reservoir. The car is in the shop now because it refused to start this afternoon, probably the fuel pump, so I should be able to get them to find the problem.
I'll let you know what it turns out to be,
Thanks for all your help

 

[wood1]

Gotya.

Let me know how it turns out

 

[Unicyclist]

Well, apparently the Explorer's crankshaft sensor died. The shop replaced it and pulled the codes, apparently there was an ABS system fault. They said that, unlike most newer cars, in this one the parking brake light comes on whenever there is an ABS fault so that's why they were both on. I don't really plan on trying to fix it, because the brakes work fine as is, and I am comfortable driving without ABS.
Thanks for all your help on this, those links are quite useful.
~Unicyclist

 

[wood1]

Good stuff dude, glad to hear you are up and running.

Like I said, I unhooked my ABS. I do all slow speed driving mind you, if I was ripping around a corner at highway speed and had to jump on the brakes ABS might just come in handy...