MoparFins

Techical Discussions => Tech- - ELECTRICAL => Topic started by: attkrlufy on February 16, 2011, 04:55:28 PM

Title: So what's this plug do?
Post by: attkrlufy on February 16, 2011, 04:55:28 PM
Today I was cleaning up the engine bay in my '79 New Yorker (360 v8) and I found an unplugged plug.  I have no idea what it's for and I can't find it in my Service Manual.  It's got a part # on it's side (3513624) but I checked my '79 Parts Catalog and that # isn't listed.  It's buried in with the wires that run through the conduit right next to the cruise control assembly - perhaps it's part of that?  My CC isn't currently working.....maybe it's related to that?

Just thought I'd try a longshot and see if any of you guys here know what this plugs into and what it's for.  You can see it located between the CC servo and the diagnostic port for the lean burn computer:
(http://i985.photobucket.com/albums/ae339/attkrlufy/Online%20posting/100_0006.jpg)



Title: So what's this plug do?
Post by: Brian on February 16, 2011, 06:09:08 PM
The black/brown wire with the socket type boot?  Well that goes down to the stud off the top of your proportioning valve....brake warning light.




Title: So what's this plug do?
Post by: Steve on February 16, 2011, 07:00:46 PM
Didn't this car have lean burn in it?  I had an 80 that didn't have it
Title: So what's this plug do?
Post by: Guests on February 16, 2011, 07:01:24 PM
That makes sense, but  the question is, WHAT THE HECK IS IT DOING ALL THE WAY UP THERE?
Title: So what's this plug do?
Post by: attkrlufy on February 16, 2011, 07:01:53 PM

Quote from: thrashingcows
The black/brown wire with the socket type boot?  Well that goes down to the stud off the top of your proportioning valve....brake warning light.
Oh that makes sense.  On my portioning valve there's four threaded openings but only three tubes coming out of it.  The fourth has a cap with a little "nub" on the end.  I guess that boot fits over top of it.

Thanks.  :)

Title: So what's this plug do?
Post by: attkrlufy on February 16, 2011, 07:04:03 PM

Quote from: dana44
That makes sense, but  the question is, WHAT THE HECK IS IT DOING ALL THE WAY UP THERE?
I have no idea.  Maybe someone did brake work on Wanda in the past and forgot to plug it back in. (http://www.moparfins.com/forum/smileys/smiley36.gif)

Is it a connection I should use dielectric grease on or does it "sense" brake pressure some other way?

Title: So what's this plug do?
Post by: Steve on February 16, 2011, 08:12:09 PM
Hah
I was looking at the srong plug.  Yup, I agree.  It looks like the plug that goes to the prop valve for the brake warning light
Title: So what's this plug do?
Post by: attkrlufy on February 17, 2011, 11:55:04 AM
Yep, it is.  Cleaned and greased the sensor and cap and popped it on this afternoon.  Glad that's back in place.  I'm lucky nothing went wrong with my brakes while it was off.  (http://www.moparfins.com/forum/smileys/smiley8.gif)

Title: So what's this plug do?
Post by: Snotty on February 17, 2011, 01:58:41 PM
If your brake waring light starts coming on or pulsating, you might learn why it was disconnected in the first place.  The valve that plugs into indicates a warnign light if the pressures in the valle drop too low.  That light can come on slightly on turns if your fluid pressure is low.
 
Even when disconnected your warning light should have still come on when you put on your parking breake - that's connected to a switch just above the E-brake pedal and is independent t teh one this plugs onto.
Title: So what's this plug do?
Post by: Steve on February 17, 2011, 04:56:14 PM
If that light is flickering in turns and stuff like that, you have a problem and better tend to it.  It is not supposed to do that at all
Title: So what's this plug do?
Post by: Snotty on February 18, 2011, 09:57:32 AM
Absolutely, but you know that people will put a piece of tape over their "Check Engine" light.  I could imagine there having been a problem and someone unpluged the sending unit wire.
Title: So what's this plug do?
Post by: Tom Dawson on February 18, 2011, 04:05:28 PM

Quote from: Snotty
Absolutely, but you know that people will put a piece of tape over their "Check Engine" light.  I could imagine there having been a problem and someone unpluged the sending unit wire.

Speaking of check engine lights, when I was a mopar service advisor, a customer came in for state inspection and his bulb was removed by another dealer in WVU, talk about lazy, the Jeep had EVAP faults in the system, the other Dealer just did not want to fix it and it was customer pay work.


Tom

Title: So what's this plug do?
Post by: Snotty on February 19, 2011, 05:07:20 PM
Had a car fail the smog check in Cali for a burned out bulb.  I had t take it back to the guy who did the previous trest two years earlier; he was fined for passing it since his notes said the bulb was out.
 
Sheesh!
Title: So what's this plug do?
Post by: Corey on February 19, 2011, 07:38:40 PM


That plug may have been why the cruise wasn't working as well not sure how the older cruise systems work
Title: So what's this plug do?
Post by: Snotty on February 21, 2011, 09:50:48 AM
Good thought Corey.  The system needs to know when the brakes are applied after all....  Hmmm....
Title: So what's this plug do?
Post by: attkrlufy on February 27, 2011, 04:02:50 PM

Quote from: Snotty
I could imagine there having been a problem and someone unpluged the sending unit wire.
Funny you should write that, Snotty.  You should go into business predicting the weather.

So I start Wanda up today in anticipation of salt-free roads (aaaaany day, now...) with that cap back in place and - wouldn't you know it - the second the car starts the brake warning light is glowing red hot like the Three Mile Island power plant (too soon?).  The E-brake is off...and yet, there it is, glowing away.

So I drive around the parking lot a bit, take a few turns, the thing never waivers.  It's glowing red.  I unplug the boot - no more light.

So that's bad.  Does it mean I need a new portioning valve?

Title: So what's this plug do?
Post by: Guests on February 27, 2011, 04:42:00 PM
....or you can simply keep it unplugged, as long as the brakes feel good.
 
Now, as far as the light goes, check the emergency brake up top where the wire connects to it to make this brake light come on. I have had the pedal not push against it hard enough to cancel this switch and have the light come/stay on myself, so it may have been disconnected from annoyance, not necessarily a bad brake problem. since there is a plug up there for a switch similar to the door jam dome light, unplug and see what happens. If the light does stay on, then you can start thinking about the proportioning valve itself.
Title: So what's this plug do?
Post by: Steve on February 27, 2011, 04:55:19 PM
Quote from: dana44
....or you can simply keep it unplugged, as long as the brakes feel good.
 


 
Na Na
 
If he unplugs the Prop Valve and the light goes out, and works normally with the E Brake, then the prop valve may be stuck.  If it's stuck, you may be doing too much braking on either the fronts or the rears
 
It can be cleaned
Title: So what's this plug do?
Post by: Guests on February 27, 2011, 05:44:41 PM
That's also why checking the emergency brake plug to make sure that is not the issue, as in stays on when that switch is disconnected, narrows down the two elements the light shows. One is the emergency brake, the other the ABS. If the light remains when the ebrake is verified not making it light, time for a cleaning. With it disconnected at the ABS proves the light goes out, but still  need to verify the ebrake is not the real culprit since the brakes still appear to work correctly. Usually the lights will go off unless the brake is applied, unless the ebrake switch is grounded and allowing it to remain on constantly.
Title: So what's this plug do?
Post by: Snotty on February 27, 2011, 07:19:39 PM
That's a good thought, but the e-brake and the prop valve light are on two different circuits.  I know this because I had the same issues when I changed prop-valves on my '70.   
 
Now, if his e-brake light never came on before your point would be the case.   But, he has not indicated that it never worked.  However... did it?
Title: So what's this plug do?
Post by: Snotty on February 27, 2011, 07:22:44 PM
Back to the purpose of that light on the valve itself.  If there is air trapped in the prop-valve, even if your brakes are working fine that light will come on.  If it is the wrong prop-valve, or the wrong sending unit, that light will come on.
 
I'd say there's a problem wuith the sending unit.  Find another from a wrecked vehicle, or buy a new one if possible and screw it on.  Plug the wire in and see what happens.
 
(All this is assuming that the light always worked when your e-brake was on.
Title: So what's this plug do?
Post by: Steve on February 27, 2011, 07:56:58 PM
Good point on the air Scott, but he would feel it in the brakes.  But he won't feel an imbalance.  One set would lock up brfore the other
Title: So what's this plug do?
Post by: Guests on February 27, 2011, 08:43:07 PM
That's why I though to check the emergency brake switch itself. Might be a false signal. Doesn't cost anything to check the switch is not working.
Title: So what's this plug do?
Post by: attkrlufy on February 28, 2011, 05:24:47 AM
Never noticed anything wrong with the brakes - but then again, I don't drive Wanda that hard.  I DO know I wish I had a little more stopping power.  But I don't think I've ever locked any of the wheels up in normal braking situations.

The light for the e-brake worked fine while the unit was unplugged.  When the e-brake was engaged the light went on.  When the e-brake was released, the light went off.  Leads me to believe the problem is somewhere in either the sending unit or the prop valve.

I've never done any brake work before, so just a point of clarification: If I unscrew the sending unit on the proportioning valve to replace it with another, won't that either a) introduce air into the brake line and/or b) send brake fluid shooting everywhere?  Even if it's not under pressure, since the prop valve is lower than the fluid reservoir, won't the liquid pour out as it seeks a common level?  This sounds like it'll make a mess.


Title: So what's this plug do?
Post by: Guests on February 28, 2011, 07:00:10 AM
Well, if the brake light worked with the ebrake being used and disengaged properly, then yes, it has to be the switch that was unplugged itself. It would be a real shame if it was the wire itself and not the switch, so, check the wire and the fluid level itself first, an imbalance in pressure will make the switch go off for starters (My 68 Charger, just last month, drove it ten miles after sitting four years in storage, was low fluid in the back, so filled it up, drove it home, light for the brake was on for the first 20 or so times I pressed the brake pedal then went off), so low fluid is the next verification. Next would be a wheel removal and check each is not leaking and that they are not frozen (I have had two rear wheels with frozen cylinders and the brakes worked enough on the front that it wasn't noticed initially), and a simple tire off the ground, have someone press the brake while you are spinning the tire and if it stops, no need to remove the drum unless you see fluid or can't hear or feel the brake engage (you should hear the springs move and the wheel will stop spinning when the brake is applied).
 
If all this turns out good, well, I guess the switch is the bad thing (you just rule out everything else out first), so, think about what happens when you poke a hole in the side of a sealed can....the drip is very slow. Since the master cylinder reservoir is sealed, unscrew the sensor and have the replacement real close and change out real fast, you may get one or two drips but it won't gush out. Be fast and clean, brake fluid is a paint eater. 
Title: So what's this plug do?
Post by: Corey on February 28, 2011, 07:55:41 AM
Actually having it lower is a good thing if you do it quick enough pull the old sending unit fluid coming from the place it is screwed imto will help prevent air getting in you may still want to bleed the system afterwards but there shouldnt be much air at all in a sense what you would be doing is gravity bleeding the prop valve and as long as you leave the cap on the master in place it shouldnt shoot out. on another note you said you would like more stopping power on thing to check for that is the adjustment of the rear brakes drum brakes have that self adjuster but those dont always work properly raise the rear end and free up the wheels so they spin and give them a turn like you spinning that price is right wheel lol if properly adjusted you should get no more that one and a half turns out of each wheel if they spin more than that they need to be adjusted. stinger11702011-02-28 12:57:09
Title: So what's this plug do?
Post by: Snotty on February 28, 2011, 04:16:52 PM
Agreed, it won't drip much.  It should be bled after anyway.
Title: So what's this plug do?
Post by: attkrlufy on March 01, 2011, 11:53:23 AM
Sorry, guys, it's not that I don't believe you, I just don't understand how the SENDER can be the problem.

My understanding of the way this system works is that within the prop valve is a metal "slider" that has a notch in its center.  If the fluid levels are balanced F&R the slider is centered in the valve.  And if there's a pressure imbalance of some kind, the slider moves either F or R towards the low pressure zone.  The sender is just a metal rod that sticks down and fits within the "gap" on the slider.  If the pressure is equalized, the sender doesn't touch the slider.  But when pressure drops, and the slider moves, it comes into contact w/ the sender - completing the circuit - and thus the warning light goes on.  It's the same principle behind the board game "Operation."

So how can the sender - a passive piece of metal - be at fault?  That's what I don't get.  To me it would seem more likely to be a problem with the prop valve or downstream in the lines, somewhere.


Title: So what's this plug do?
Post by: Guests on March 01, 2011, 01:25:53 PM
Case in point, why I said it may be a wire grounding problem, not the valve, unless the reason it was disconnected was because the "slider" is jammed one way or the other and can't get unstuck by itself. A small piece of debris may have made it ground out. It the brakes work and you don't have a pulling issue or the brakes don't lock up, ummmm maybe there was a safe reason to unplug it for less than the hassle of trying to repair a simple light being stuck on.
Title: So what's this plug do?
Post by: Snotty on March 01, 2011, 05:12:30 PM
[/QUOTE]


 
When I swapped my front drum brakes for disks I needed to swap the sending unit.  I asked the same question, "Why?"  Because it was not calibrated for the amount of fluid that flows to disks, which is considerably more than that of drum brakes.  That's how I learned about the unplugged wire - I did it to mine because I was getting a false reading.
Title: So what's this plug do?
Post by: Snotty on March 01, 2011, 05:13:41 PM
Quote from: dana44
unless the reason it was disconnected was because the "slider" is jammed one way or the other and can't get unstuck by itself. A small piece of debris may have made it ground out. It the brakes work and you don't have a pulling issue or the brakes don't lock up, ummmm maybe there was a safe reason to unplug it for less than the hassle of trying to repair a simple light being stuck on.


 
I agree.  If the sending unit is bad, putting another one in is a quick and easy way to learn that.
Title: So what's this plug do?
Post by: Snotty on March 01, 2011, 05:14:07 PM
It's a lot easier to swap that unit than the whole prop-valve, beleive me!
Title: So what's this plug do?
Post by: attkrlufy on March 04, 2011, 06:50:14 AM
Well, I think I'll first have someone put a tester on this circuit - hopefully it's just a bad ground.

And if it's not...sheesh.  I really don't want to put on a new proportioning valve assembly. (http://www.moparfins.com/forum/smileys/smiley6.gif)