Moparts

Help! No Dash Lights

Posted By: DUFFMAN

Help! No Dash Lights - 05/21/09 01:12 AM

Last night the dash lights on my 1972 Coronet quit working. Everything else works, guages, directionals, etc, just the instrumanet cluster lights, radio lights and shift indicator light (column shift) aren't working.

Of course the first thing I checked was the fuse and it was blown, I replaced it and it blew again. Anybody ever have this problem? Any idea where to start diagnosing it?
Posted By: 68HemiB

Re: Help! No Dash Lights - 05/21/09 02:27 AM

No dash lights symptom is more often than not a failed rheostat [dimmer] portion of the headlight switch. The diagnosis (and for some, the permanent "fix") is to jumper across the connections at said dimmer switch.

The problem with that cookie-cutter solution is that it addresses the typical fail to an OPEN circuit. You clearly have a dead short to ground, rather than an open.

Therefore, what I would do were I in your shoes would be to DISCONNECT the wires into/out of the dimmer before jumping across them. If the dead short is in the dimmer... problem solved (either permanently, or until you replace the switch). If you still have the dead short (blowing fuses) after taking the dimmer out of it, revert to standard short-chasing techniques.

Just one man's opinion and educated guess. There will be others, I'm sure.
Posted By: camdog440

Re: Help! No Dash Lights - 05/21/09 03:03 AM

Make sure it is grounded properly.
Posted By: DaytonaTurbo

Re: Help! No Dash Lights - 05/21/09 03:03 AM

My dad had the same problem in his 71 satellite back in the 80's. His solution was to pull out a cigarette lighter and read the gauges by the light of the flame!

Do you have a multi-meter? If not I suggest getting one, even a cheapie one, makes finding the problem easier than trying to use a 12v test light.
Posted By: NachoRT74

Re: Help! No Dash Lights - 05/21/09 03:25 AM

definitelly you have a short LOL

I bet you lost also parking lights... is the same fuse what everything you told plus parking lights.

So you will have to check socket by socket on exterior lights, and also glove box.

BTW, Cluster lights have an extra fuse, just to the output of dimmer to all the dimmer controled net ( cluster, radio dial, ashtray, accesories lights and console or column shifter dial ), but I don't think probably existant short is related to dimmer net since that fuse SHOULD blow first, unless dimmer fuse is overrated. Is one of the top fuses, and is separated from the buss bars, with an orange wire on back.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 11:09 AM

All the exterior lighting is working.

Is it possible that a burn't out bulb is causing the short?
Posted By: RapidRobert

Re: Help! No Dash Lights - 05/21/09 11:33 AM

Quote:

Is it possible that a burn't out bulb is causing the short?

Not from just burning out(open). As 68Hemibee said it's a dead short to ground & I would start at the headlight switch(the rheostat)
Posted By: therocks

Re: Help! No Dash Lights - 05/21/09 01:18 PM

I have seen a burnt bulb create a ded short but they were the tail light bulrs.Wire inside broke and hit the grounded socket.Ive seen it twice in 40 years.Like suggested you have a dead short so your grounds should be good.Like suggested pull the switch and disconnect the wires.See if the fuse blows then.Rocky
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 01:36 PM

In case it matters, my dome light still works off the headlight switch.
Posted By: 68HemiB

Re: Help! No Dash Lights - 05/21/09 04:31 PM

It is interesting that your dome light still works, to the extent that it might be interesting that your cigarette lighter still works - they are electrical, and in the same car. However, they are not part of the same circuit with which you are having the problem.

I side with Rocky in that it has happened in the history of mankind that a bulb's filament has broken in such a manner as to short to ground with very little resistance/load. This happens in large bulbs with beefy filaments, and in a frequency to be well under statistical significance. A burned out bulb, especially in something as small as a dash lamp, is going to be an OPEN.

What is causing your fuse to blow is almost certainly a special type of "short" circuit - one that is a DEAD SHORT to ground, with no load or "work" being done by the electrons on their way to ground. The circuit is very simple, with very little going on, and a component notorious for failure along the way.

Admittedly, some of these points might be subtle, and not immediately apparent to someone who has not spent decades working on cars. Other concepts, however, should be as basic as they come - what happens when a bulb burns out, what makes the fuse in one circuit blow repeatedly, and the nature of a dead short...

...especially when the one posing the questions is a trained engineer who sees fit to belittle the unwashed masses, both in threads on the General Board, and his sig line [edit: Yes, I see you just now changed it]. Imagine us being foolish enough to think a car should be equipped with a dipstick for the transmission.

I was planning to bite my tongue, and just offer polite help, until I read your followup questions.

Perhaps your dash lights are out because of the presence of a "caveman stick" in your car somewhere...
Posted By: Runner2go

Re: Help! No Dash Lights - 05/21/09 05:19 PM

Your killing me....

Why would you assume a trained engineer would understand the age old concept of "a short to ground".
Surely a simple Renaissance Short must not exist in his car... for this is truely the work of gremlin's.

I think I'll go check my trans with a Caveman Stick... while I still have one.


Duffman, the "Multimeter" is your freind
Posted By: NachoRT74

Re: Help! No Dash Lights - 05/21/09 05:59 PM

Quote:

All the exterior lighting is working.



which fuse blown ? then blown one of the top ones, number 5 I think... dunno why I thought was the other one, the one what feeds the input to the dimmer switch


Quote:


Is it possible that a burn't out bulb is causing the short?



no
Posted By: NachoRT74

Re: Help! No Dash Lights - 05/21/09 06:06 PM

Quote:

It is interesting that your dome light still works, to the extent that it might be interesting that your cigarette lighter still works - they are electrical, and in the same car. However, they are not part of the same circuit with which you are having the problem.




no, dome light and cigar lighter are both in diff lines on 71 and laters B bodies

cigar lighter and glove box lights are same as parking lights on the same fuse that feeds the INPUT to the lights switch. Then the light switch does have two outputs from that input... one to feed directly the exterior lights and the other one what is coming out from built in dimmer, and then does have the extra fuse, what apparently is the one blowing.

Head light switch does not have fuse, is a direct source from batt with its own input and output.

So the 71 and lates B bodies light switch ( and many other Mopars with built in dimmer switch too ) carries two positive inputs and three positive outputs... then carries one ground output to turn on the dome light

Dome light positive input is constant directly to bulb ( is switched on by ground ) and comes from hazzard flasher splice, the same line than brakes, trunk... shares same fuse.

------------------------

you have a short somewhere in the orange line, ( dimmered source ) it could be gear light, clusters lights, Ashtray light, Radio dial light, or Accesories light. Look at the accesories light feed ( tripple female rubber plug ) close to A/C-Heater control. Maybe some metalic piece get inserted on plug and is grounding.

Radio plug orange wire could it being crimped accidentally on some removing job. same about the light to gear dial if you did some recent job at column.

Maybe some cluster socket wire jumped out from socket somehow and is shorting. If is standart cluster, the clock or delete plate does have its own wire and socket for a while the rest of cluster is a pin on the printed circuit board multipin plug
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 06:47 PM


First of I'm an ME not an EE. I know a little about electrical, I had too to get my degree, but not enough to do a failure analysis. So your comments are out of line.

I understand that I have a short, I'm just trying to find help in determining what component(s) could cause it so I can minimize the amount of work need to find the problem. A lot of times there are known, common failure modes and that is what I'm looking for.

BTW the dome light switch is at the end of the rheostat for the dash lights, and since the dash lights stay illuminated while the dome light is on I thought the fact that it still worked might be relevent. Forgive me if I'm not 100% familiar with the design of a headlight switch in a 37 yo car.

Since the cheapest and easiest place to start is the headlight switch I'll begin there. Thanks to all who responded with useful information.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 06:51 PM

Quote:


Why would you assume a trained engineer would understand the age old concept of "a short to ground".



Isn't calling it a "short to ground" kind of redundant? Don't all "shorts" go to ground?

Quote:

Surely a simple Renaissance Short must not exist in his car... for this is truely the work of gremlin's.



No actually I think there are penguins under my dash chewing through wires.

Quote:

I think I'll go check my trans with a Caveman Stick... while I still have one.



While you're at it adjust the points and pop in an 8-track.


Quote:

Duffman, the "Multimeter" is your freind



Yes I own a multimeter and know how to use it. As I stated abouve I'm just trying to shorten the time it takes me to diagnose it by attacking common failure modes first.
Posted By: 68HemiB

Re: Help! No Dash Lights - 05/21/09 06:55 PM

Quote:

Isn't calling it a "short to ground" kind of redundant? Don't all "shorts" go to ground?



No. Short circuits are circuits that go somewhere other than intended - to ground or to another circuit.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 06:57 PM

Quote:

**You are ignoring this user**

Posted By: 68HemiB

Re: Help! No Dash Lights - 05/21/09 07:11 PM



I realize that you aren't reading this.

But others can still see what a meanie I am. That final straw of helping you with the definition of "short" is real fightin' words.

Bad Steve.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 07:23 PM

BTW Engineers spend most of there careers specializing in a certain topic, and they strive to become masters of that topic. Very rarely is an engineer a "jack of all traits".

As for the dipstick subject, in that thread I was defending the engineer(s) who removed it because none of us knew the rational behind the decision. I was giving reasons why it might of been removed when a bunch of you continued to insist that all engineers are idiots. Once sombody else jumped in to help support my position you all went silent. I guess if you can't gang up on somebody it's no fun huh?
Posted By: stumpy

Re: Help! No Dash Lights - 05/21/09 07:26 PM

"jack of all traits". The term is Jack of all trades. No we just got tired of you not listening to those of us that keep up with our own vehicles.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 08:09 PM

Quote:

"jack of all traits". The term is Jack of all trades.



Actually if you google it both come up, both ways seem common.

Quote:

No we just got tired of you not listening to those of us that keep up with our own vehicles.



You wern't listing to those of us who live the reality of engineering everyday either, so what's your point?

How convienent that you where one that ran off:
https://board.moparts.org/ubbthreads/show...part=9&vc=1

You mechanics think your all knowning just because you work on cars all day. The reality of engineering is we do a lot more than just design something, we have to do a little marketing, sales, accounting, supply change, logistics, and other things. When it's all said and done we have to understand the whole package not just the design. That's why many of us become masters of a certian thing, we have to.
Posted By: stumpy

Re: Help! No Dash Lights - 05/21/09 08:33 PM

Go back and reread your google sites and you will find most say that traits is wrong.
You may do all of that but it has absolutely nothing to do with actual hands on. Just because it works on paper doesn't mean it works in the real world. Like I said you didn't run us off we just got tired you saying the same nothing over and over again just to defend a poor engineering choice.
BTW if engineers are so good how come there are so many recalls for poorly desinged parts a systems?
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 09:13 PM

If mechanics are so good then how come there is so much re-work?

Do you have any idea what goes into designing a car? Do you have any idea how many things can go wrong, how they are abused or used improperly? I think engineers do a pretty good job considering the infinite variables they have to deal with.

Fine it's "Jack of all trades", I was wrong. Big deal. Yes I can admit I'm wrong sometimes, but who isn't? I take it you've never made a mistake in your life?
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 09:16 PM

Quote:


You may do all of that but it has absolutely nothing to do with actual hands on.



I forgot to add that I have to be a mechanica and a fabricator too. Hardly a day goes by that I don't have a wrench in my hand either at home or at work. This statement shows you have no clue what engineers actual do. How do you think prototypes and/or concepts get built?
Posted By: stumpy

Re: Help! No Dash Lights - 05/21/09 09:23 PM

Again more blah blah blah. My grand father and father were engineers. Gramps was the guy that designed the lighting system for the original Tiger stadium in Detroit and my father was a design engineer for Chrylser in the late 50s so I do know something about engineers. Including the fact they can make mistakes and not all their designs are good.
It's been fun reading your blathering but I'm done and have better things to do. I have a spare trans to build and a stroker motor to put together. Good luck with your light problem.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/21/09 09:32 PM

Give that man a Cookie!
Posted By: buildanother

Re: Help! No Dash Lights - 05/21/09 09:37 PM

So it is the inst fuse that is blowing ,so the problem is inside the car. I would start looking under dash at any lighting type wiring for cigar, dash lights etc. Maybe it's just a dangling extra wire that found its way to ground? Will it blow the fuse even if the dimmer is turned down all the way?
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 11:06 AM

Last night I went to work with the multi-meter and heres what I found;

-With the headlight switch unplugged there is still continuity to ground, thus the switch is not the problem.

-With the instrument cluster disonnected there is NO continuity to ground. This rules out the wiring from the fuse and points toward the instrument cluster itself.

-Interestingly with all the bulbs removed from the instrument cluster the fuse still blows.

I guess the next step is to remove the instrument cluster itself and visually inspect it.
Posted By: Mr.Yuck

Re: Help! No Dash Lights - 05/22/09 12:21 PM

Quote:

Last night I went to work with the multi-meter and heres what I found;

-With the headlight switch unplugged there is still continuity to ground, thus the switch is not the problem.

-With the instrument cluster disonnected there is NO continuity to ground. This rules out the wiring from the fuse and points toward the instrument cluster itself.

-Interestingly with all the bulbs removed from the instrument cluster the fuse still blows.

I guess the next step is to remove the instrument cluster itself and visually inspect it.



Voltage regulator???? Current runs thru the dash via the guage. Maybe you are getting too much juice?
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 01:40 PM

I thought about the voltage regulator, but all my gauges are still working. If the voltage regulator was bad wouldn't they be dead?
Posted By: Mr.Yuck

Re: Help! No Dash Lights - 05/22/09 01:49 PM

I don't know, they could be fine, just your panel is getting too much juice somehow. Easy enough check. Vot regs are like $13.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 02:04 PM

I checked 2 local parts stores, one wanted $38 for it the other $60.

That's why I decided to diagnose it first rather just start replacing parts.
Posted By: Mr.Yuck

Re: Help! No Dash Lights - 05/22/09 02:17 PM

Quote:

I checked 2 local parts stores, one wanted $38 for it the other $60.

That's why I decided to diagnose it first rather just start replacing parts.



Advance Auto
"BWD Voltage Regulator
Part No. R296Z
OE Style
Warranty 1 YEAR REPLACEMENT IF DEFECTIVE
Offer Price: $15.29"
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 02:39 PM

R296Z Is a charging system voltage regulator, not the instrument cluster voltage regulator (limiter).
Posted By: Mr.Yuck

Re: Help! No Dash Lights - 05/22/09 02:53 PM

Quote:

R296Z Is a charging system voltage regulator, not the instrument cluster voltage regulator (limiter).



yeah that's the one I'm talking about...unless they blow as soon as you turn the key???? otherwise you have a short someplace. Did you hit the cluster reg w/ the tester?
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 03:14 PM

Quote:

yeah that's the one I'm talking about...unless they blow as soon as you turn the key????



The fuse blows with the key off and the headlight switch on.

Quote:

otherwise you have a short someplace. Did you hit the cluster reg w/ the tester?



Not yet. Next I want to check continuity to ground with it removed.
Posted By: Mr.Yuck

Re: Help! No Dash Lights - 05/22/09 04:04 PM

aren't electrical problems fun? I have a headlight switch in route, no dash lights yet. I hope that's it.
Posted By: DUFFMAN

Re: Help! No Dash Lights - 05/22/09 04:54 PM

Quote:

aren't electrical problems fun?



No Doubt.

A friend of mine had a 1986 Daytona with dead dasdh lights. He brought it to the local Dodge dealer (this was inthe mid 90s), 2 days and $500 later they still hadn't found the problem. After that he just lived with it until he sold the car.
© 2024 Moparts Forums