I installed a Parts Place Tic Tac Tach in my 1970 Olds 442 a few months ago. Ever since I did that the dash lights are always on if the car is running. Also I can not adjust the brightness. Today I noticed the headlight switch was extremely hot after going for a 20 minute drive. Anybody have any ideas on these issues? Are they related? I’m new to working on cars so any help would be appreciated

 

Double check your wiring.

 

along with the check your wiring; check to be sure the tic tach is well grounded (check all the gauges). You have an always hot lead for the clock in the tachometer.

 

And until you sort it out, don't drive the car. Don't ask me how I know this.

 

Well that sounds catastrophically ominous.

 

We can assume the dash lights were working correctly prior to your installation - they were not ALWAYS ON and the rheostat contained w/in the headlight switch operated correctly and allowed you to increase &/or decrease the brightness of the dash lights.

Suggestion w/ regards to check your wiring. I would start by tracing where &/or what wire you (probably) installed incorrectly into the dash lights. You might consider removing that wire(s) and get back to square one so the dash lights are working once again - e.g. the rheostat of the headlight switch can increase/decrease brightness of the dash lights. It would appear you're feeding a hot live wire into the headlight switch - somehow, I don't know how, but if the headlight switch is HOT, you know that ain't right. Worst (or Best) case scenario right now is to remove all the wiring from the tach installation and get back to square one when all the lights were working.

Did you review the several installations threads regarding Tic Toc Tach installation on this site. There are some good threads on wiring up the Tic Toc Tach. You're not the first one who has had an issue wiring up a Tic Toc Tach. You might post a picture and others can help you identify which wires to where.

 

You might review this thread (below). Examine Post #2. Do you have the 1970 CSM? There may be additional information in the 1970 CSM, as Alan (Post #2) suggests for the 1972 CSM - I don't know. As suggested, maybe in the 'Accessories' section of the 1970 CSM.

https://classicoldsmobile.com/forums...s-where-66352/

 

Probably going to be the same wiring...see Post #2 (in the link below).
Are you wiring this up w/ OEM standard contact points & coil, HEI, or Petronix?

1972 tic toc tach wiring

 

It wasn't pretty.