dashboard electrical question

drbobj67

New Member
Sep 22, 2006
59
0
0
The instruments lights on my dashboard are all out and I don't know if it is related but the cigarette lighter doesn't work. When I rotate the headlight switch, which is supposed to dim or increase the instrument lights nothing happers but the dome light does come on when I turn it all the way. But the headlight switch may still be the problem. I checked the fuses nothing is out. Any hints on where to start looking for the problem? I'm not an expert on reading wiring diagrams but I was going to start with the electic meter and start testing for power comming out of the headlight switch.

I have a extra auxillary cigarette lighter outlet it has two prongs on the back. What is the best way to wire it up? I was going to go right off of the fuse box, unless there is a better way to go.
 
  • Sponsors (?)


headlight switch

As I mentioned I did check the fuses previously but I'll check them again.

I'm thinking that it's the switch. Is there a trick to taking it out. I tried some channel locks on the bezel. Does it screw off? I did not want to scratch up the bezel with the channel locks.
 

Attachments

  • headlight switch.jpg
    headlight switch.jpg
    19.2 KB · Views: 389
Pull the knob to the ON position, and then press a small button on the flat side of the headlight switch by reaching up under the dash. The knob & shaft will then pull all the way out and off. You'll then see a '+' shape over where the shaft goes in. Use a large flathead screwdriver to unscrew this central piece. Then the bezel will come out from the front and the switch will drop down from the rear.
 
I figured that the + had something to do with it. I don't know why I did not check my shop manual first. But now if anyone else on the forum needs the info it will be there.

Only problem now is I don't seem to have a screwdriver wide enough and I think the switch has been removed already, the + is a little stripped. I'll get it eventually either a loaner screwdriver from an auto parts store or maybe I'll have another one at home. WCS I'll buy another tool.
 
First, the problems are not related, unless someone has been doing some re-wiring under there.

When you get access, maybe this will help with the troubleshooting:

HLSwitch.jpg


Check power coming out of the I (Indicator) terminal while rotating knob. If bad, replace switch. If good then check at fuse (Blue/Red wire). If power is good on both sides of fuse, then the connection at the back of the dash panel to the indicator lamps may be faulty.

As far as the auxilliary lighter outlet:

Make sure you know which prong is the ground (Outer ring in outlet) and which is 12v (inner-center portion at back of socket)

Ground is obvious, but the 12v hookup point could piggyback on the existing lighter feed. If you are plugging in high current items, you might want to run a new fused feed from battery side of the solenoid.
 

Attachments

  • HLSwitch.jpg
    HLSwitch.jpg
    68.1 KB · Views: 4,323
Tim, Thanks for the Diagram that will definitely help. I assume that it applys to a 67 I notice you have a 65. If that doesn't help me test it nothing will. BTW where did you find that diagram?

As far as the Aux mostly I'll be running a cell phone charger, which doesn't draw much and once in a while a small tire pump, that will probably need the fused feed.
 
making progress

I got the switch out and using the diagram from Tim65GT I did some tests. With the switch out of the car I used the multi meter (I'm still learning about it). With it set on Ohms to test for resistance, I put one lead and D1 and one on D2 when I turned the switch all the way which turns on the dome or courtesy light the meter went from 1 to 0 which means there was a completed circut. I did similar tests using B to P and H which is the battery to parking and to headlights when I pulled the switch out to the appropriate postion the meter went to 0. But when I used B and I which is to the instruments and turned the switch nothing happened. That looks to me like that switch is history.

Right about that time one of the wires in the lead on the meter detached. Oh well I need to get out the solder gun before I can check the power to the unit that plugs into the switch. But I think I already found the problem.

BTW if anyone has a similar diagram for the ignition switch on a 67 let me know. I'll start a seperate post about it.
 
Tim, Thanks for the Diagram that will definitely help. I assume that it applys to a 67 I notice you have a 65. If that doesn't help me test it nothing will. BTW where did you find that diagram?

I made 'em.

I got the switch out and using the diagram from Tim65GT I did some tests. With the switch out of the car I used the multi meter (I'm still learning about it). With it set on Ohms to test for resistance, I put one lead and D1 and one on D2 when I turned the switch all the way which turns on the dome or courtesy light the meter went from 1 to 0 which means there was a completed circut. I did similar tests using B to P and H which is the battery to parking and to headlights when I pulled the switch out to the appropriate postion the meter went to 0. But when I used B and I which is to the instruments and turned the switch nothing happened. That looks to me like that switch is history.

A better way to check is with the switch removed, but still plugged in to the harness. You probably have to remove the gage panel for beter access.

Use your meter set to volts and ground the black lead(-) and back probe the connector with the red(+) lead. Check first for Battery voltage on the B input and then go through and check the other terminals output as you actuate the switch positions. If the diagram checks out, then the 67 is then same.

If you have no voltage on the I output as you rotate the switch, Make a test jumper and verify that your indicator lights work by going across B to I.
 
Tim65GT said:
I made 'em.

A better way to check is with the switch removed, but still plugged in to the harness. You probably have to remove the gage panel for beter access.

Use your meter set to volts and ground the black lead(-) and back probe the connector with the red(+) lead. Check first for Battery voltage on the B input and then go through and check the other terminals output as you actuate the switch positions. If the diagram checks out, then the 67 is then same.

If you have no voltage on the I output as you rotate the switch, Make a test jumper and verify that your indicator lights work by going across B to I.

nice job on the headlight switch diagram :nice:

I tested the switch removed from the plug because I did not see a way to access the tabs without removing it. Not sure what you mean by the gage panel, there is a metal cover over the back of the switch but it is riveted on, doesn't look like something to be removed. I did try a jumper to bypass the switch to see if the dash lights would come on and no go. So I pulled the fuse again, I could see the wire still in it but I used the meter on the ohm setting and it tested bad. So I put in a new one. I tried to jumper test the dash lights and no go. Pulled the fuse and it had blown.

So now it looks like I'll be looking for a short or open circut. just what I was hoping not to have to do. I'm still learning about using the meter, anyone have any pointers or know a good book or link on using the multimeter for auto electric diagnosis? The manual that came with it only gives specific instuctions on what to hook up where for battery, alternator and tach testing etc. What I need is the basic theory behind testing and how to trouble shoot for shorts.

I may have not needed to take the time testing the switch but I figure it is a learing process and the same principles will apply to the next thing that goes out. It's always good to take a systematic approach and find out what works and what doesn't before you go and start replacing a bunch of parts that were good to begin with.
 
So I pulled the fuse again, I could see the wire still in it but I used the meter on the ohm setting and it tested bad. So I put in a new one. I tried to jumper test the dash lights and no go. Pulled the fuse and it had blown.

So now it looks like I'll be looking for a short or open circut.

When a fuse blows, its a short circuit, not an open. In your case, it would appear that the switch is not bad. Because the instrument panel fuse blows, then it is getting power from the switch. Some where in the distribution of power to the multiple indicator lamps, the current is going to ground (or a very low resistance component).

Not sure what you mean by the gage panel, there is a metal cover over the back of the switch but it is riveted on, doesn't look like something to be removed.

By gage panel, I mean the panel that houses the gages...Speedo, fuel ect.

If you remove it (which you should do next anyway) It would be easier to access the light switch area.

Remove the gauge panel...the hardest part will probably be disconnecting the Speedometer cable.

Remove the indicator lamps and look for anything out of the ordinary, such as cracked insulation or melted blue/red wire. Check each socket and bulb with your meter. They should be more than 20 Ohms. Look for any wiring that maybe tapped into the blu/red wire. Like an aftermarket radio.

View attachment 429480

I think the light in the console for the shifter is on the same circuit. Look for a possible short there too. You could look for a plug under the dash behind the console with a blue/red wire. Unplug it and see if your problem goes away.
 
more electronixs diagnosing

I was studing auto electic books last night and the schematics from the shop manual. I think I was looking at the auto trany shifter light in the schematic but I don't remember if it was part of the same circut. After a while and when it gets late they all blur together. :bang:

Also I did learn that an open will not allow a circut to work but won't blow a fuse, it has to be a short like Tim65gt said. So somewhere there must be some wires crossed. I did notice that the radio shares some of the same connections as the dash lights. I did not mention it but my radio doesn't work either. It is a cheap replacement I put in years ago after the nicer one was stolen, so I thought it had maybe just stopped working. And I don't remember if it was hooked into the existing radio wireing or not.

Also when I checked the bulb for the tranny shifter - Oh!! whats this its blown.

So with my "know enought to be dagerous" knowledge about auto electronics you can imagine what I'll be getting into over the weekend. I've already had the instument guage pannel loose before to check the wiring harness underneath, I've done the spedo cable a few time but never undid the plugs to take the instrument guage panel all the way out. But looks like I will.

The only thing I wonder about it that when I put the new instrument light fuse in I don't think I had the headlight switch back in because I was planning on using a jumper to check the instrument lights without going through the switch. So I wonder could their be a short upstream from the switch? But I'll be taking a good look at all the wiring in the instrument guage panel, the tranny shifter light and the radio, most likely I'll have the console out to get a better look at everything.

Thanks again for the help from stang net :hail2: it sure makes a difference.
 
So I wonder could their be a short upstream from the switch?

No, the power for the instrument lights originates at the switch. If there was a problem "upstream", the other light circuits would not work.

Current goes from the switch, thru the fuse then to the instrument lamps.
 
no power to fuse ?

Well here is the latest in my testing.:bang:

Since the new fuse blew when I put it in I have not put in another fuse yet. So with no fuse in for the dash lights I tested and found power to the radio and power to the wiring in the console I think it only goes to the light for the shifter and two lights at the rear of the console, with no signs of broken, crossed or frayed wires.

I have no power to the fuse on either side. Which is kind of strange because I would think I would have needed power to the fuse to blow it. I gues I'll take a closer look at the tabs where the fuse slips in and see that they are clean.

Also I removed the dash instrument panel and tested with the meter set on ohms for continuity to each of the lights from the connector that I undid to remove the dash instrument panel, they tested OK. Also I tested for continuity from one of the tabs where the fuse slips to one of the dash lights and it checked out OK.

If the current goes from the switch to the fuse and then the dash lights then I guess I'll try jumping the switch and see if I get power to the fuse. I do get power to the batery terminal of the connector that plugs into the headlight switch.

The search continues.
 
I have no power to the fuse on either side. Which is kind of strange because I would think I would have needed power to the fuse to blow it. I gues I'll take a closer look at the tabs where the fuse slips in and see that they are clean.
Make your voltage check at the fuse tabs again, make sure the switch is pulled out and turned all the way to bright (CCW)

If you could rig up a high current bulb such as a brake light and jump it across the tabs in the fuse box in place of the instrument panel fuse, it would light up when the short is present.

As you disconnect or remove items in the circuit, the light will go out or light very dim when you find the area that is causing the problem.

That way, you don't blow a fuse every time you think you may have found something and you want to test it.
 
Tim65GT said:
Make your voltage check at the fuse tabs again, make sure the switch is pulled out and turned all the way to bright (CCW)

If you could rig up a high current bulb such as a brake light and jump it across the tabs in the fuse box in place of the instrument panel fuse, it would light up when the short is present.

As you disconnect or remove items in the circuit, the light will go out or light very dim when you find the area that is causing the problem.

That way, you don't blow a fuse every time you think you may have found something and you want to test it.

That is a GREAT idea. Lean something new every day here on stangnet =)

When I had an auto in my 67 the shift indicator bulb kept poping my fuse. To this day I don't know why because there was no apparent short in that part of the circuit. I fixed that problem by puting a T5 in my 67. No more auto shifter, no more bulb to blow my fuse lol.
 
As I mentined before I'm still new to figuring out auto electonics. For some reason I was only testing the headlight switch disconnedted. I did not realize till yesterday that to test the headlight switch with it connected all I had to do was use the leads from the meter on the wires comming out of the back of the conector to the switch. DUHH!!!

So now when I tried the test that Tim65GT recomended

"Check power coming out of the I (Indicator) terminal while rotating knob. If bad, replace switch. If good then check at fuse (Blue/Red wire). If power is good on both sides of fuse, then the connection at the back of the dash panel to the indicator lamps may be faulty."

So I tested the wire to the I terminal of the switch and when I rotated the knob on the headlight switch I did get voltage, It went from 0 to 3 as far as I could tell.

Also as I type this I realize now that when I was testing for power to the fuse I probably did not have the headlight switch turned on. Another dumb mistake, but at least I'm starting to figure it out. So I have something else to try when I get home.

And I can also rig up a brake light bulb as a tester. One of these days I'll get this thing figured out.

Thanks again for the help, especially Tim,:SNSign: