Need help slaying electrical gremlins (1 Viewer)

[smokeater]

Morning mudders,

I’ll preface this by saying that I’ve exhausted the FAQS and Search Fx to remedy my issue, finding some answers but not all the info I need.

This week I’ve embarked on a mission to dial in all the loose ends (aka gremlins) that were left after installing my new harness purchased from Coolerman back in 16’.

Really, I was left with completing the horn circuit (recently restored a H and L elephant horn, one I had and the other I bought off eBay in a pair) found I would also need new horn relay which is on the way. This also led me down the rabbit hole of restoring the steering wheel and horn button too. Needless to say, I’ll be golden here when the relay arrives.

Secondly, I had work to do on the lighter circuit. My OEM lighter was toast. I picked up a new one installed it and after some head scratching and a new fuse (best to disconnect the battery before attaching hot wire) got it operational. I cleaned up my inspection socket and got it hooked up next.

Third, I had a ground issue that was causing my turn indicator lights to glow when the headlight switch was pulled as well as too low of current in the right turn signal switch that wouldn’t cycle the flasher. I remedied this after figuring out that my front turn signals weren’t grounding well enough because the fender holes are rusted and the bottom brackets that support the light don’t exist. So... following Coolerman’s turn signal grounding modification, running a ground wire from the housing bolt to body, no more issues there. (That guy’s a genius!)

Fourth, every time I pulled the Front drive lever I’d blow the 20A lighter fuse as well. After tracing the wires back from the switch on the transfer case I happened upon some luck at the harness connection under the hood. I realized that the wires in and out of the male and female connector weren’t matching eachother so I tried swapping the wires around so they corresponded color-wise. I locked the hubs, pulled the FD lever and bam!! 4wd indicator light worked with no blown fuse.

I’m feeling pretty good at this point, learning how to effectively use my multimeter, trouble shooting problems logically, canvassing ih8mud for answers to questions that’d come up, and also becoming proficient at reading the wiring diagram. So I decided to tackle the Brake light that I’d never seen light up!

Which brings me to my current roadblock! I pulled up and researched the diagram for this circuit and understand that several things will cause this light to illuminate when the ignition is in the on position...(low brake pressure and parking brake engaged) One way Coolerman suggested I check the light is by grounding one of the brake pressure switch connections...this worked, the bulb lit up. I grounded the other connection and same thing. I moved to the parking brake lever. The brake was engaged and no light. I pulled everything off, cleaned up the contacts on the lever housing and the switch...no luck! I opened up the switch and cleaned all internal connections. While I had it apart I plugged it into the harness, grounded both prongs on the switch separately and boom! light turned on! I put the switch back together pushed in the button and no dice! I connected the switch back up to the lever (figuring it needs ground) and adjusted it so that when engaged the button is not depressed and when brake is off the button is depressed. (I think this is the correct setup) I figured I’d test the switch in place so I found out which of the two wires is pushing 11.7 volts and attached it to the switch. I left the other side unattached and pulled out my multimeter switching it to DCv200 setting, grounded the black probe and attached the red probe to the free bullet off of the switch.....11.7 volts with brake engaged, O volts when disengaged. Next I tested the resistance to see if I was getting good ground. I attached my meter to each of the bulleted leads from the switch, one to red, one to Black. I set the meter on OHM200....brake engaged 7.2-8.7ohm, brake disengaged nothing. I’m thinking the switch is good at this point, but why no light?

I have not ventured to look at the brake switch at the pedal...I did however read that the brake light had a check function where when illuminated, you can depress the brake pedal and it would shut off. When I had the parking brake switch apart and both prongs grounded (light on) I tested this and when the brake pedal was pressed, the light did NOT go out.

Any help would be appreciated, I’ve exhausted all my ideas at this point.

Thanks

Smokeater

 

[ginmtb]

That switch has two positions - very subtle but if you pull it out again you will see like I did in this video:



So adjust carefully it doesn’t take a lot to throw it off. Hopefully this is your solution like it was mine.

Check out my thread on brake light issues might help:

Help brake lights stuck on... :(

 

[smokeater]

Thanks for dropping me a line, I reviewed your thread, it was promising at first, then I realized that my 70’ switch is different than the one for your 74. My post is not nearly as long and doesn’t have a positive detent.

 

[smokeater]

Ginmtb,

Just reading through your thread again, I’m wondering if I misunderstood you when you referred me to make sure their are two clicks, you are talking about the brake switch on the pedal aren’t you? I thought you were talking about the parking brake switch....I’m wondering if the brake switch is adjusted too far in hampering the full recoil of the switch and not allowing 12v flow to the other side of the circuit ( or possibly keeping it open so the light isn’t tripped to turn on) . Does this make sense?

 

[ginmtb]

Yeah sorry the brake switch on the pedal. Very sensitive to adjustments if it is dialed in too far it won’t return all the way which could be your problem with the red light not turning on. But the two switches are tied together (see below). When the park brake is on a light tap on the brake will turn the red light off. Or releasing the park brake will turn the light off.

 

[smokeater]

Well, that was almost
disastrous....I pulled the brake switch out and cleaned the leads, thought I’d also take a look inside, not such a great idea! About 45 minutes later I managed to get the switch back together and operational. It for sure doesn’t have two detents and made no difference in the parking brake light operation...thanks for the suggestion though ginmtb! I at least can rule that out.

Anyone else have any suggestions ??????

 

[ginmtb]

Could your switch be bad? Should have that second detent. The switch is still available and good for as far back as 7/70...

 

[ginmtb]

Does it look like this?

 

[smokeater]

Yes, that looks like the one. I think I understand that the first “click” is the plunger pushing into the two prongs or B-B’ on the schematic, The audible click is the mechanism I had to put back together that makes contact at the end of the housing where the GW wires attach (A-A’).

I’m going to dig around today some more...I think that my switches work, but I’m going to throw the multimeter on both and see if I can determine the distance or setting when the plunger engages the prongs on each. If I understand the schematic correctly, the plunger needs to rest between these leads in order to illuminate the light by grounding.

When you adjusted yours, did you start the switch all the way in and work it out until everything was good, or the other way around?

I’m questioning how I can adjust both switches using the light as my guide if both switches are out of adjustment? In other words, do they both need to be adjusted correctly for the circuit to work?

What should I be looking for, as far as OHM readings when the plunger is between the two prongs, effectively closing the circuit?

Thanks for all your help man, I think I may get this thing whooped, with your help!

Smokeater

 

[ginmtb]

Sorry I can’t remember what I did. But if you get under there you will see how they work and can adjust accordingly. You will get this! Try not to overthink it these are simple vehicles lol.

 

[ginmtb]

Actually the more I think about it I think because I was having issues with my brake lights staying on, I adjusted that first. It was draining my battery so that was critical. Then I adjusted the park brake switch so the light came on. I’m sure there was some tinkering between the two afterwards but not much if I recall...

 

[smokeater]

So....when you adjusted the brake switch, did you adjust it out until the lights went off with the brake out/at rest?

Ok, so a got into my truck a bit ago and started at the brake pedal, I adjusted her all they way through her range in small increments. At no point did the light illuminate through this process (ignition was on and e-brake was pulled) I left her adjusted at the point where with the slightest pressure of the pedal will make the switch "click."

I moved to the parking brake switch, I spent some time looking over the diagram and wondered two things: Will the light illuminate when the switch circuit is closed (parking brake disengaged) or open (parking brake engaged)? Also I noticed that the circuit grounds through the brake booster, is this done through the mounting bolts, or is there some other grounding wire I can't locate?

I got to thinking my issue might be a grounding issue because when I ground either of the brake warning switches on the master cyclinder AND the parking brake is engaged, the light illuminates, when I release the parking brake the light goes OFF. This tells me that the parking brake switch is GOOD.

So I ask, do you have any separate grounding wires on the switches or the brake booster/master cylinder? note: My rear lights are grounded as described in the diagram.

 

[ginmtb]

The light will only illuminate if there is a fluid issue with the master cylinder (not good) or when the parking brake is engaged. The light will go out with the parking brake engaged when you step on the brake pedal. Once the parking brake is released the light will go off.

I don’t have any separate ground wires that I’m aware of for the brake booster. Is your master cylinder connected as shown in the schematic? That will give you the light while driving should you develop a hydraulic leak and fluid gets low.

Again can’t remember what I did for the brake adjustment but I’m fairly certain I adjusted it out fully and then moved in.

 

[ginmtb]

The connections to my master cylinder:

 

[smokeater]

Man, that master cylinder is clean, as are those switches! Mine are nowhere near that clean, when I decide to replace my brake lines, I’m going to have some cleaning to do.

I have the same setup, I’m pretty sure the break booster gets its ground from the mounting hardware to the firewall, I didn’t see any gaskets that would insulate it.

Thanks for the photo to confirm!

-Smokeater

 

[Coolerman]

As you already know, the brake switch has two sets of contacts, one for the brake lights (Switch A Green/White wires: This is a normally OPEN switch and closes when you press the brake pedal) and one for the low pressure circuit (Switch B Red/White: This is also a normally open switch and closes when you press the brake pedal).

To test the Low Pressure Circuit Brake switch contacts:
Put your meter in low ohms mode. Measure across the two Red/White wires. When the pedal is NOT pressed you should read an open or infinity on the meter. When you press the pedal the meter will read close to zero ohms. (Same test for the Green/White wires to verify the stop switch is working)

To Test the E-Brake Switch:
The E-Brake switch is also normally open and closes when the E-Brake is engaged. Unplug the switch and put the meter across the two wires coming from the switch. (These can be Red/White or Green/White or solid Green wires) When you engage the switch the meter will read zero or very low ohms.

To Test the Low Pressure Master Cylinder Switches:
Put your meter in low ohms mode. Put the black lead to a good ground on the body or frame. Put the red lead on the button contact on the bottom of one of the switch where the connector fits. You should read zero or very low ohms when the brake pedal is NOT pressed. When you push the pedal down and build pressure the switch will open and the reading will go to infinity or very high ohms. Test the second switch the same way.

 

[smokeater]

Thanks for the detailed information Mark, I’m going to get this thing figured out! This is last item to correct, got my inspection socket operational, lighter, 4wd Light, and my horn relay is being delivered today!

Thanks

Garrett