72 Wagoneer: Brake lights not working

Stock FSJ Tech Area
Post Reply
User avatar

Topic author
W300
Posts: 50
Joined: Tue Sep 28, 2021 5:48 pm
Location: Oregon

72 Wagoneer: Brake lights not working

Post by W300 »

Hey all,
Finally got the brakes working on my Wagoneer, but I have no brake lights. Turn signals work and running lights, so I know the bulbs are fine, and from the wiring diagram in my TSM, it appears that the brake lights are fed through the turn signal switch. I cleaned up the contacts on the hydraulic switch on the master cylinder, and tried just connecting the two wires manually, still no lights, so I don't think it's the hydraulic switch. Any suggestions on how to troubleshoot further?
1972 Wagoneer
360, TH400, D20, Limited Slip
PTO Winch
User avatar

Stuka
Site Admin
Posts: 11789
Joined: Thu May 12, 2011 5:53 pm
Location: CA
Contact:

Re: 72 Wagoneer: Brake lights not working

Post by Stuka »

Have you tested the switch that gets released when the brake pedal is depressed? The circuit won't be completed unless that switch is activated.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
User avatar

tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: 72 Wagoneer: Brake lights not working

Post by tgreese »

The hydraulic switches are very troublesome. If present, that's the only brake light switch, and it should light when you short across it.

About all you can do is trace the wires with your multimeter or test light. Someone will correct me, but as I recall, these Wagoneers have a single 1157 bulb in the tail lights that provides both the brake lights and indicators. If so, I suspect the problem is in the turn signal switch, since the indicators work. The logic of the brakes-or-flashing-indicators is there in the turn signal switch, as I recall.

Look at the wiring diagrams on the Tom Collins site - https://oljeep.com/gw/elec/GW_wiring.html

1972 has interesting line drawings of the harnesses, which may or may not help you. You can look at the diagram for '71 or '73, though I suspect '73 was the first year for the GM locking column and may be confusing for that reason. You have the earlier style column. If you don't have it, I suggest you get the TSM for 1972, cheap on CD-ROM at RockAuto. There are instructions there for removing and diagnosing the turn signal switch.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
User avatar

Topic author
W300
Posts: 50
Joined: Tue Sep 28, 2021 5:48 pm
Location: Oregon

Re: 72 Wagoneer: Brake lights not working

Post by W300 »

Stuka wrote: Mon Jan 10, 2022 11:23 am Have you tested the switch that gets released when the brake pedal is depressed? The circuit won't be completed unless that switch is activated.
It's a 1972, so it's got the hydraulic switch on the bottom of the master cylinder. I used a test light to confirm I've got power on one side of the connector, and shorted across to the other side with a bit of wire, still no lights, so that leads me to believe it's between there and the turn signal switch. That doesn't mean the hydraulic switch couldn't still be an issue, but right now there is definitely something else wrong.
1972 Wagoneer
360, TH400, D20, Limited Slip
PTO Winch
User avatar

Stuka
Site Admin
Posts: 11789
Joined: Thu May 12, 2011 5:53 pm
Location: CA
Contact:

Re: 72 Wagoneer: Brake lights not working

Post by Stuka »

W300 wrote: Mon Jan 10, 2022 3:09 pm
Stuka wrote: Mon Jan 10, 2022 11:23 am Have you tested the switch that gets released when the brake pedal is depressed? The circuit won't be completed unless that switch is activated.
It's a 1972, so it's got the hydraulic switch on the bottom of the master cylinder. I used a test light to confirm I've got power on one side of the connector, and shorted across to the other side with a bit of wire, still no lights, so that leads me to believe it's between there and the turn signal switch. That doesn't mean the hydraulic switch couldn't still be an issue, but right now there is definitely something else wrong.
Yeah, I forgot the older ones had that setup.

Electrical gremlins are rarely fun to track down.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
User avatar

Topic author
W300
Posts: 50
Joined: Tue Sep 28, 2021 5:48 pm
Location: Oregon

Re: 72 Wagoneer: Brake lights not working

Post by W300 »

Yeah, and there’s a lot of splicing and crimping of wires under the dash. Not sure what PO was doing, but it makes it tricky to trace stuff using the wiring diagrams. I was able to trace the brown wire to the base of the column, shorted across the hydraulic switch and my test light lights up, so I know it’s at least sending the signal into the column. I then hooked the hydraulic switch back up, and pumped the brakes and get the signal at the column, so the switch is working.

Looks like I have to pull the steering wheel to get to that signal switch.


Sent from my iPhone using Tapatalk
1972 Wagoneer
360, TH400, D20, Limited Slip
PTO Winch
User avatar

1978J10REDWHITE
Posts: 263
Joined: Fri Nov 20, 2020 7:25 pm

Re: 72 Wagoneer: Brake lights not working

Post by 1978J10REDWHITE »

I've found typical a wire sheath has a wear thru point or "pinched damages" on this type or scenario.
Dd they ever work for you as the owner?
So you said power is at one side of the SWT.
Do a real good underside inspection of the wire harness looking for mounting around other things like cable or Hard brake line mounts.
Could be a poor ground of the wire end, to frame is needing cleaned real good.
If correct then verify SWT functions Reliably, when brakes are applied, might need to create a "McGiver" type wire/lamp setup, to check power-continuity there, then go down the line to locate the culprit.
Each section , verify power is present to each leg & conn point.
User avatar

Topic author
W300
Posts: 50
Joined: Tue Sep 28, 2021 5:48 pm
Location: Oregon

Re: 72 Wagoneer: Brake lights not working

Post by W300 »

I am worried about cracked insulation and rub through on the wires, but I haven't actually found any bad wires yet. They are stiff though, so it wouldn't surprise to find an issue in the future. So far my battery is maintaining it's charge while sitting, I've always had the terminals disconnected when I'm not working on it. So that's a good sign that I don't have some short somewhere.

I don't recall if they have ever worked since I got the truck. I could have sworn I noticed one of them on after bleeding the brakes once, but it might have just been the turn signal, I know I've done that in the past few days.

The strange thing is the turn signals work just fine, only the brake lights don't work. Per the wiring diagrams, the power is fed through the same wires, so I know the turn signal switch can send power back there for signaling on both sides, it just won't work for the brake. If I have an issue with the hydraulic switch in the future, I'll McGyver mount a new switch at the pedal.

Not looking forward to pulling the steering wheel... who knows what other issues I might uncover!
1972 Wagoneer
360, TH400, D20, Limited Slip
PTO Winch
User avatar

timwiller
Posts: 40
Joined: Sun Oct 06, 2013 5:49 pm
Location: Fordland MO, near Springfield

Re: 72 Wagoneer: Brake lights not working

Post by timwiller »

from one who's been there...i had a problem with just the left brake light. after weeks of chasing wires etc. i found out that wiggling the turn lever to the right the brake light came on. so the switch. future todo.
doesn't fix anything but helps elimination. good luck
1966 J-3600 Gladiator. 304, T-18-D20 [twin stick] ,D44-D53, magniflow exhaust
Your 50 year old FSJ IS your hobby!! :lol: :lol:
User avatar

Topic author
W300
Posts: 50
Joined: Tue Sep 28, 2021 5:48 pm
Location: Oregon

Re: 72 Wagoneer: Brake lights not working

Post by W300 »

Pulled the steering wheel and have access to terminations on the signal switch.
The hazard switch doesn't work at all, and actually prevents the flashers from working when engaged. Maybe that's what is causing the issues? My TSM says the emergency flashers are on a separate circuit that is powered directly off the battery, and uses it's own heavy duty flasher relay.
Anybody have experience with the emergency flasher switch in an early steering column?
1972 Wagoneer
360, TH400, D20, Limited Slip
PTO Winch
Post Reply