Rheostat questions, I have two different models.

[Dino]

The rheostat in my car didn't do anything.  Dash lights were always the same and I could only light the roof light when I opened the door.

The car came with a spare switch and when I rolled the wheel all the way up it would click at the end, unlike the one in my car.  I was hoping this one would be OK and I'd do the swap this spring.  Today I removed the old switch, set them side by side and there you go, they're different.   
The one that came out of my car is on the right in the pictures.  Although there's many differences, the overall size is the same, the other switch would fit.  How can I check if the switch works apart from installing it in the car which I cannot do for months to come?

[gtx6970]

the one on the left is 1970 and the one on the right is 68-69 they are completely interchangeable

[Dino]

the one on the left is 1970 and the one on the right is 68-69 they are completely interchangeable

Excellent!

Would you happen to know if it's normal that the 68-69 does not click at the end of the thumbwheel turn and the 70 does?

Could I somehow test these switches with a electrometer or something?

[moparfan53]

I also was recently wondering how to test the switch. Below is info I found online. I have not tried it yet so cannot say for sure if it is correct. If you try it would you post if it is correct/works? Thanks

"How to bench test a 68-70 B body dimmer switch  

EZ to test...
2 terminals go through the rheostat for this use an ohmeter on low resistance scale. When turning the control the resistance should vary from about 12 ohms down 0 ohms (continuity).

For testing the 3rd terminal when the control is rotated all the way, this will be grounded to the controls frame and the ohmeter will show 0 ohms (continuity).

3rd terminal is top, when knob is all the way up/dome light on/"

[68neverlate]

Would you happen to know if it's normal that the 68-69 does not click at the end of the thumbwheel turn and the 70 does?

I have a '68 and had the rheostat out of my car this past winter and can tell you that it wasn't a click more than it was just a noticable increase in resistance when turning the wheel... for what it's worth.     

[Dino]

Okay, so I tested my original rheostat and it's not doing anything, no reading whatever I do.  I grab the '70 switch and it gives me the readings as outlined by moparfan so it seemed like this owuld work.

I put the instrument cluster bacl in the car yesterday and low and behold...the '70 rheostat isn't working either.  I'm at a loss, where do I look next?  Any fuse I need to check first or any other way to test everything?

As it sits, the instument cluster lighting seems to be on high but I cannot control it nor can I flick on the dome light with it.

[68neverlate]

You might want to confirm the wiring coming into the connector that attaches to the back of the switch.

You should have a double yellow, a double (black/dark green) and a single tan.  The double black/dark green should be your 12 volts (it will only be hot when the headlight switch is either in the middle or full-on positions).  The tan is the output from the rheostat to control the dash light intensity and the double yellow is the switch output for the dome light.  The tan goes to the fuse box and comes out orange to the dash lights.   

Was the switch working mechanically (wheels all turning) before it went in?

[Dino]

You might want to confirm the wiring coming into the connector that attaches to the back of the switch.

You should have a double yellow, a double (black/dark green) and a single tan.  The double black/dark green should be your 12 volts (it will only be hot when the headlight switch is either in the middle or full-on positions).  The tan is the output from the rheostat to control the dash light intensity and the double yellow is the switch output for the dome light.  The tan goes to the fuse box and comes out orange to the dash lights.   

Was the switch working mechanically (wheels all turning) before it went in?

I really didn't pay any attention to the connector so I'll start with cleaning it up and checking the wiring itself.  The switch itself seems to be working fine but then again I'm pretty bad when it comes to electrical.

[Slotts]

 

[71ChallengeHer]

Slotts does fantastic work. He is a long time member of cuda-challenger.com and a very good friend of mine. He restored the grille in my 71 Challenger and did a fantastic job. 

[Dino]

Holy cow I totally forgot to reply to your post Slotts!

I'll pm you regarding the switch.

[Dino]

Since I had all these gauge issues going on I didn't focus on the switch much anymore.  When I reinstalled the cluster on Saturday I noticed someone spliced the wires behind the switch so I removed it, reinstalled the '70 switch and guess what?  It works!  Dash lights dim and interior light goes on in up positions BUT it's very very touchy, I can't always make it go on so next time I have the cluster out I'll clean up the connections.