dash lights still weird

[alini]

I added a ground to my dash lights, by placing an eyelet under one of the mounting screws for the circuit card.  Initial test were positive and I thought I was good.   This past weekend we replaced the incorrect fuel tank sending unit, and with the lights OFF the gas gauge works perfect.  Problem is once I put the headlights on, the dash lights no longer work and the gas gauge goes to E.

 

I already took the ground wire right out of the dash plug and made it connect right to a fresh ground and I left the previous added ground in place.  Still no joy.

 

Anyone one got any suggestions or should I start looking at swapping out that circuit card.  I have power getting to the card since all the dash warning lights have power/ground and work correctly but the dash lights and gas gauge seem to have something in common to the ground that is not playing fair.

[petelempert]

Alini-Assume when you replaced the sending unit, you got the correct ohm unit for your year model? Not sure that could could cause your squawk, but just thought I'd ask. PRL
 

[alini]

I had replaced the unit. I did have the wrong one installed but it is now correct and with the lights off the gauge is accurate.  Verified with a full tank of gas.  Once I turn the lights on the gas gauge goes to zero and I have no dash loghts

 

i am studying a picture of an uninstalled circuit card and I'm seeing numerous possible ground circuits.  They may be power.  The wiring diagram I am using is horrible since I am not at home with the laminated card and can't verify wiring color.  But I did find the gas gauge and dash lights do use the same ground circuit so I just need to verify I have my grounds hooked to the right spots

[petelempert]

Alini-Since the gauge works without lights, I'd keep trying to find a good ground for the light circuit. PRL

 

[KongaMan]

Are your idiot lights also affected when you turn the lights on and off?  Don't start the car, but turn the ignition switch to Run and see if the oil pressure, hot and cold temperature, and alt lights go out when you turn the lights on.

 

What about the turn signal indicators, high beam indicator, and parking brake lamp?  Do they all work irrespective of the lights?

 

Finally, does this happen only when the headlights are on or also when just the parking lights are on?
 

[alini]

Everything works correctly until I put the headlights on.  Once they are on the turnsignals and hi beam indicator come on slightly and the gas gauge goes to zero, with no dash lights    I know its a ground issue  just need to find a good spot to connect to and make sure the ground is good as well.   I have bigger issues now that need more attention

[KongaMan]

Turn on the headlights and turn off the dash lights.  Do you have the same symptoms with the gauge and indicators?

 

Check all your lights (headlights, parking, tail, license plate -- anything that comes on with the headlight switch).  Do any of them look burned out or dim?  You might have a bad bulb that's bleeding off the power.

 

I had a turn signal bulb go bad once.  Every time I turned left, my dash lights started blinking.

 

If your gauge, dash lights, and turn signal indicator are all acting funky, you should also check the idiot lights to see if they also go out when the lights come on.  IIRC, all of that stuff is grounded through the panel connector.  Which raises the obvious question: Did you try wiggling the panel connector?  

 

Edited September 24, 2016 by KongaMan (see edit history)

[alini]

I got under the dash this afternoon after the show.   I studied the routing of the circuits on the dash and the wires installed.  I found it funny that all the circuits involved were on the pins on the upper side of the connector.  All the lower pins are the power and output for the warning lights.  The upper side is the dash lights, turn signal, hi beam and gas gauge.  

While I was messing with the connector I noticed some of the dash lights would flicker....so I stated pressing around on the circuit card itself and as I pressed in the middle between the turn signals and hi beam light suddenly all the dash lights worked correctly and with the key on the gas gauge went up while the lights were on.....so working as advertised.

 

So I need a new circuit card.....problem solved....once install the new one

[KongaMan]

Those cards are pretty straightforward. You might have nothing more than a bad solder joint or a dirty pin.  Even a broken trace is not that big of a deal.  If you're already committed to pulling your board, you might make a careful inspection of yours before you summarily condemn it and buy another.

 

If you can get the connector off and get access to it, you might try a little DeOxit contact cleaner and work it back and forth a couple of times.  And make sure that it's fully seated.  When you're coming in from under the dash, it's easy to get it a little crooked so that the lower pins are fully seated while the upper are not.  That might be all it takes -- and you won't have to pull the dash.

Edited September 25, 2016 by KongaMan (see edit history)