Some electrical questions

It's times like these I really miss my old high school buddy Monte. The kid was a wiz at automotive electrical and he was so thin and wiry, that he could really curl up under any car's dashboard. I always left any electrical work in my car up to him.

Any way I have a couple of things I could use some help with. First is about the heater blower motor in my '65 Chero. I blew a fuse the other day and when I opened the hood to look at the motor I notice a big hole in the case. The hole is about the size of a quarter, maybe a little less and I can see a big part of the armature though it. My question is, should this hole be open? I live in the Pacific North West and it looks like a good place for water to get into. (That what I think happened to blow the fuse) The motor case was obviously built with this hole in it, but I'm wondering if it was to facilitate the installation of the motor components and then plugged. On the other hand I don't want to cover/plug it if it's supposed to be opening for cooling or some other reason.

Second is I want to install a tachometer and I'm wondering where the best/easiest place is to tap into for both the 12vdc input supply and the input for the tachometer light. This is for an aftermarket tachometer.

Thanks for your help,
Scott

 

I think there is a hose that goes to the motor that hooks up to the box, think it moves air through the motor but been a while since I looked at one.

 

Yeah, my Olds had that, I think. Sort of a bypass, for something or another.

 

The hole is for a rubber hose, It does provide air to cool the motor. Usually it will attach on the heater box, shouldn't be open where water or lots of dirt could get in.

Tach neg lead dist neg........ usually but there are excetions, positive could be hooked up nearly anywhere there is key on power. If there is not a fuse where attached install an inline one with a small enough fuse to protect the circuit. Check the tach directions if available. Should be a fairly easy deal.

 

Yeah I have the instructions, I was just wondering if someone might know the easiest/most accessible place to tap into. Guess I'm either going to have to stand on my head or drop the dash out.

Thanks all for the info on the hole in the motor, I didn't see anything like that in the manual but it makes sense.

Scott

 

Ok I installed the tach and spliced into one of the wires going to one of the dash/gauge lights. Everything works right except no light on the tach. I know the dash lights come off a 5 vdc switching regulator, so I was wondering if the tach light needs the full 12vdc?

In that case I was thinking of splicing into ths input to the headlight dimmer switch. Wadda you guys think?

Thanks,
Scott

 

Nope Scott, the voltage regulator only powers the guages. The lighting circuit is separate, usually a light blue with red stripe wire. That light wire comes from the dimmer in the headlight switch. Depending on your wiring harness there might be an unused female connector for dash lights close to the ashtray, or at the radio power connection. No separate ground wire for the tach ? You may have to ground the tach case to get the light to work.
You may have a bad bulb in the tach also.

 

Ok so taping into the dash/gauge light should work then? The tach has a separate ground wire and is hooked up. I used one of those splice connectors and may not have gotten a good connection, I'll try again.

Thanks,
Scott

 

Hunt that skinny blue and red wire to tap into. The tach's ground wire might only be for the guage movement, you may have to ground the shell of the tach to get the light to work.

 

Thanks for all the help with this, I really hate automotive wiring, only part of working on cars I don't like. Anyway as you know I had hooked up my tach but the light didn't work. Well the other morning, as I left for work, I hit the high beams and the light in the tach came on. Seems the light I tapped into was not just one of the dash lights, but the lamp that lights the hi beam indicator dash light. I had to laugh at myself and I figured I share it with you.

Scott

 

Well, the good news is you figured out what you did wrong. Better news it was nothing major, or something wrong with the unit itself.