Tachometer and Radio won't power up

[ih8vols]

Hey guys. I have a 79 C10 Silverado. Other than the few minor things I've done to it, it's all original. I've been doing some upgrades and fixing her up a bit.

I finally got the radio installed and it was working fine. A few weeks later, I started noticing the truck was running rich. I then decided to install a tachometer so I could adjust the carb. I decided to use the power running to the radio to power the tachometer. Now, neither the tach or the radio works.

I checked the fuse and it's fine. Any ideas? Should I find another source to power the tach? I'm very much a newbie with cars, so break it down in laymen terms.

Appreciate the help!

Here's the tach I put in: http://amzn.to/1rz9TXx

Here's my radio: http://amzn.to/1T5fd14

[ih8vols]

Any ideas? Thanks.

['76 Big Block]

First thing I would check would be ground connections for both items----disconnect your tach (since the radio was working before you installed it)--- basically back retrace your steps.
I wouldn't wire the tach and radio in the same circuit---
Most aftermarket tachs have specific wiring instructions as to where wires go----sounds like either you missed a step or your tach is defective--- that's a cheap price by the way (for the tach)
Good Luck!

[Axle]

Swap the fuse (or do a voltage check on both sides of the fuse while its under load.

I can't tell you how many fuses I have come across that had a cracked filament. All looked fine visually, some checked out fine with an ohm meter, but putting a real load on them flexed the filamnent just enough to open the connection.

Alex.

[chrismoore701]

I have two fuses for my radio. Be sure you check both