Dash brake light randomly illuminates

[BennyGGG]

Dash brake light randomly illuminates. Sometimes it stays on from start up and will turn off within 10-15 min of driving. Other times it comes on and off while driving.
 

It’s not the parking brake. That appears to be working properly. When the parking brake is engaged the dash light comes on. If I start to drive it will flash. When I release the parking brake it extinguishes.

 

 Brake fluid looks good. Upgraded to 3rd Gen brakes up front and did a full brake job 4 months ago. Had no issues until now. Only recent maintenance is new tires. They are 34s. 

 

this issue also seems to cause cruise control to not work. 
 

possible speed sensor issue? I’ll double check tire pressure tomorrow. None of them look low. 
 

any advice is much appreciated 

[IBMobile]

Check the connector at the rear axle for starters

[Doubletrouble]

 Also, make sure your parking brake is fully disengaged. The return spring gets weak and will allow the pedal to hang a bit. Mine does this so when I release it I will bump it up with my left foot as I release to make sure it's fully seated in the off position.

[Mopar1973Man]

Make sure the slack adjustment is tighten properly. If the slack is excessive the pedal will hang down and touch the pin switch for the brake light. So ad just a few turns to the slack adjustment on the cable and it should stop.

[BennyGGG]

I appreciate the replies. Ill

check the connector, slack and parking brake return today 

[BennyGGG]

Nothing out of the ordinary with the rear connector. It was secure. No water, dirt or corrosion inside the connector. 
 

The parking brake engages and disengages property. I took the switch out and gave it a quick cleaning. There doesn’t seem to be any excessive slack in the system. 

[dripley]

Since it messes with the cruise control I would think its on the brake pedal, like in the switch. That will disable the cruise. I dont know a good way to test that though. If you remove it you have to replace it per the FSM. There is rachet or some sort mechanism in it that exktends and cannot be pushed bck. I am not totally sure of that since I have never messed with mine. I have new one at the house for when I put new bushings on the pedals. I think there is a lever on it you have to engage to prevent that then relese it after install. Been a while since I looked at it though.

[BennyGGG]

I saw the switch has “do not reinstall” printed on it. I didn’t want to mess with it. I’ll look into this being an issue. Thanks for the reply. 

[Mopar1973Man]

Actually... The tail light switch (brake pedal) that can be reset and re-used. There is a ratchet kind of stem adjustment I managed to open that switch up and extend the plunger and re-assemble with no issues. 

 

As for the Parking Brake light on the dash its the cable slack adjustment needs to be tighten a bit more. The pedal is not fully returning up. Be careful rusted cables will do this same thing but as you adjust you just start dragging the parking brakes because the cable is too rusted out and sticky.

[BennyGGG]

2 hours ago, Mopar1973Man said:

 

As for the Parking Brake light on the dash its the cable slack adjustment needs to be tighten a bit more. The pedal is not fully returning up. Be careful rusted cables will do this same thing but as you adjust you just start dragging the parking brakes because the cable is too rusted out and sticky.

Doesn’t the parking brake cause the light on the dash to flash? 

[Doubletrouble]

 Is there a way to.lubricate the parking brake cables?one seem to work ok but do have a little sticky feel to them. 

[Dieselfuture]

5 minutes ago, Doubletrouble said:

s there a way to.lubricate the parking brake cables?

Fluid film oh man I'm a salesman for it now after getting some for myself. They just need to send me free samples now.

[dripley]

9 hours ago, Doubletrouble said:

 Is there a way to.lubricate the parking brake cables?one seem to work ok but do have a little sticky feel to them. 

Graphite. Any oil down the cable will attract dust and debris.

[Doubletrouble]

So a graphite cable.lube would be best. I may have some for my motorcycles. I'll have to look. 

 Thanks.

[dripley]

Used it on mine too. worked well.

[BennyGGG]

Quick update. Last week I found that several of the wires that connect to the brake light switch had gotten hot at some point. This is still a very new truck to me. There is also a trailer brake controller wired in. Unfortunately it appears to have been installed by a poorly trained ape haha. I left the brake controller installed but will definitely have to take care of that mess soon. As for the wires to the brake light switch, I repaired and heat shrunk them. So far the light hasn’t come back on.  I’ll keep you posted. 

[Dieselfuture]

On 1/3/2021 at 5:28 PM, BennyGGG said:

Quick update. Last week I found that several of the wires that connect to the brake light switch had gotten hot at some point. This is still a very new truck to me. There is also a trailer brake controller wired in. Unfortunately it appears to have been installed by a poorly trained ape haha. I left the brake controller installed but will definitely have to take care of that mess soon. As for the wires to the brake light switch, I repaired and heat shrunk them. So far the light hasn’t come back on.  I’ll keep you posted. 

Switching to led bulbs would help to reduce amp draw on wires. 

[Doubletrouble]

4 hours ago, Dieselfuture said:

Switching to led bulbs would help to reduce amp draw on wires. 

@Mopar1973Man sells LED replacements in the forum store if you want to go that route. (Just a little free advert for ya mike!)

[BennyGGG]

After a couple weeks now I’m pretty sure I solved the issue. I replaced the brake light switch that actuates with the brake pedal. No more intermittent issues. As always, Thanks for all the help! 

[Mopar1973Man]

Out here it would be best to force oil down the jacket being amount of salt on the roads will eat the cables and graphite is not going to protect from rusting.