New Tachometer Problem

[bds32]

Need advice on a problem please. 1970 Chevy K10 with HEI. I installed a Summitt racing tach this morning and when it is receiving power, I get smoking and odor coming out of vent on top of dash. Unhooked, no smoke. I have tried two places in fuse box, both spliced with something else. One was electric choke, the other was radio. Tried two different ground spots, lower dash and firewall inside engine compartment. Hooked tach wire to Hei open connection Fourth wire is for lights which I plugged into Lts cluster feed. Everything seems to work except the smoking which I know means I have messed something up. Ideas?

[VetteVet]

Does your tach connect like this?

http://static.summitracing.com/globa...um-850512b.pdf

It's pretty straight forward except you won't need the orange fuel injection wire.

Check the red wire for continuity to the tach body, the tach may be shorted internally.

[bds32]

well it seems similar. Mine is this one: https://m.summitracing.com/parts/sum-g29105

My instructions say to use 12v switched source so I tried it with electric choke which is plugged into ignition unfused. Then tried radio. Both of those have inline fuses. I did not hook directly to ignition. Only other difference is the white wire for lamps.

When you say check for continuity, you mean just put a tester on red wire and check that way? It works when plugged in. Forgive my ignorance. I appreciate the response. Other issue is I lam out of town as of today, so I can't check it now anyway. Thanks.

[VetteVet]

Originally Posted by bds32

well it seems similar. Mine is this one: https://m.summitracing.com/parts/sum-g29105

My instructions say to use 12v switched source so I tried it with electric choke which is plugged into ignition unfused. Then tried radio. Both of those have inline fuses. I did not hook directly to ignition. Only other difference is the white wire for lamps.

When you say check for continuity, you mean just put a tester on red wire and check that way? It works when plugged in. Forgive my ignorance. I appreciate the response. Other issue is I lam out of town as of today, so I can't check it now anyway. Thanks.

Continuity means there is a connection between two or more points that will allow electricity to flow between them. You could use a test light if it had it's own power source to light the light when you touched between two points that were grounded. Normally I use a multimeter on the ohms scale and look for very low ohms. You cannot use it on anything that has live voltage on it or it will burn out the meter. To test for continuity with a multimeter you would put the meter on the Ohms scale and touch the red lead on one point and the black lead on another and watch the meter for a low or zero reading. If you got that it means there is a connection between the two points.There are several U-Tube videos that show how to use the multimeter.

If your tach body were shorted to the red power wire internally, when you applied power to the tach power wire,(red) it would be the same as connecting the red wire to ground and would cause the red wire to burn up.
It should have blown the choke fuse if that were the case. I recommend that you connect directly to the IGN-Unfused terminal on the fuse panel but use a fuse in the red power wire to avoid burning up any circuits in case the tach is shorted. A 10 amp should be plenty.

[bds32]

I have a multi-meter so I will check that out when I get back. Thank you for excellent response.

[bds32]

Hey Vet,

I wanted to let you know that after finally returning from vacation, I used my analog multi-meter and after watching the video and setting the ohms' meter to highest setting then adjusting the ohms dial to 0 when connected, everything seemed to check out with the continuity. This is with the red power wire unplugged. I checked all of the visible wires on the tach and saw no problems. I hooked the power wire by itself into one of the unfused ignition ports and ran an inline 10 amp fuse with it. Hooked up ground and lamp wire. I left the tach green wire unhooked and held the tach
on seat (no metal contact at all, and the housing is plastic anyway.) Then started it. Within a minute, started getting smoke from the same vent, top of dash in front of driver's seat. I could smell it below dash under steering wheel. I have looked as best I can without removing anything but I cannot see the source of the melting wires. I checked the fuse and it is good. Cannot figure out what is going on. I've unhooked for now and everything runs good. Still think it is probably the tach shorting out somehow?