Red brake light and RABS light is on on my 89 F150XL 4x4 5.0 4sp.
Anyone has suggestion on what to check first?
Is there a good post on how to read code out of RABS? Black/Orange wire to ground to activate while engine running?

Also the rear brake locks up sometimes even I don't step on the brake so hard.
could it be a related problem?

 

I previously had RABS light on problem with 91 Mazda Navajo(Explorer deal), only RABS light came on and Speed sensor was open. replacing speed sensor on this car solved the problem. Now, on 89F150Red brake light never goes off. It's my understanding that if Red brake light is on the problem is either Brake fluid level sensor in resevor or parking brake switch failure?

 

Red brakelight is for: emer brake, fluid level? (not sure if you have fluid level in 88/89). dual brake indicator (loss of pressure either front or rear). ABS fault turns both red and ABS lights on, ground then disconneci BK/O lead with ignition on after fault displayed - I believe the fault code is lost if you turn the igniton off before grounding then disconnecting the test connector - read codes 0 to 16 - 1,12 and 16 not used.
Post back if you get codes. I believa there is info on ABS in forum but have not checked the site myself - reading 88 manual.

 

Thanks for your reply.
I'm not getting any code.
This truck does have brake fluid level sensor.
hope I can fix this today.

Thanks,

 

how can I test brake fluid level sensor?
there is no positive on any of 3 wires that goes to that sensor as i tested them with my light testor.

 

Are you sure the ignition switch was on when you were checking for power?
Check fuses 10 and 18 in dash fuse panel; disconnect fluid level indicator connector one Pink/White lead has a resistor inline and may not read a full 12v, power should be on one P/W lead with igniton on. The black lead should go to ground. Try reading from the black lead on the reservoir switch to both P/W terminal pins one at a time - if you have continuity the switch is bad, fluid is low or the float is stuck in the reservoir. This will give you both ABS and Brake warning lights. Good luck.

 

I was having the same exact problems on my 88 Bronco. The brake systems are the same. I was getting both dummy lights on and everyonce in a while my rears would lock up. I replaced my ABS valve and it solved them problem. The ABS valve can usually be found on the inner frame under the drivers front side. Just follow the brake lines to it. You can check the electrical and make sure it is connected to it properly. My valve had a bad o-ring and it leaked into the electrical and shorted it out. I had to special order it from the Zone for around $100.

 

I shorted blk/org wire while engine was running with RABS/Red lights on.
No brinks at all. I will check out fluis level indicator per your instruction, hopefully this afternoon.

Kameronth, did you get any code while you were having this problem at all?
sounds like problem might be the valve or combination of valve and other things?

 

No, I did not even try to pull the brake codes since they were different from the check engine codes. There is only a few things that would cause that and I replaced my master cylinder, so it led me to believe that it was the abs valve.

 

I removed the fluid level sensor and checked for continuity and couldn't find any continuty between 3 terminals on sensor. I took one out of my 91 Mazda Navajo(same as explorer) and checked but same thing. since I already had them out I swapped them. ploblem fixed! It was the fluid level sensor after all. I'd like to Thank everyone for assisting me on the issue!

 

For clarification continuity would be in the actuated condition installed with the float at bottom low fluid, so when you removed it it should read open. Since it is magnetic it could be just too close. Glad you got it fixed and don't forget to fix the Navajo.

 

Hey, thanks again. I totally understand about continuity, I wanted to see if the sensor from 89f150 was malfunctioning. I couldn't tell the difference between two by checking them electrically. They do look different, color, shape by little. one from Navajo must be updated version by couple of years. I guess new one I will be getting from the dealer would be even more updated.