tach goes crazy

[rjc157]

Just got my tach back from nisonger for the second time and it reads way off and when driving just goes crazy they feel its a bad ground somewhere ,where do I start and what do I do its a neg ground car with a alt conversion ,could the coil have gone bad any help appreciated

 

[Patrick67BJ8]

Just got my tach back from nisonger for the second time and it reads way off and when driving just goes crazy they feel its a bad ground somewhere ,where do I start and what do I do its a neg ground car with a alt conversion ,could the coil have gone bad any help appreciated

"they feel it's a bad ground somewhere"...I'd check behind the tach and make sure there's a black ground wire securely attached to the tach bracket. Also take an ohmeter and read the tach case to a known good ground for continuity.

 

[Healey Nut]

Run a temporary wire from the back of the tach direct to the main ground either on the battery itself or where the battery is grounded and try it . If that solves it you have a ground problem .

 

[RAC68]

Hi Ralph,

Is there anyone close by that has a negative ground Healey and will be willing to connect and test your tachometer. This would verify whether the tach is performing and the cause is in your electricals. If it turns out to be in your connections, how many loops are in your white ignition wire. Last, and this is a question that just needs mentioning, are you sure the returned tachometer contains the negative ground modifications I assumed you installed before sending?

Although I agree with the Healey Nut's alternate ground suggestion, the ground to the tachometer is shared across all the gauges and, if it were not present, I would expect your panel lights would not work.

Good luck,
Ray (64BJ8P1)

 

[rjc157]

Everything works this is the second time I got it back I went to the shop and they showed me that the needle is spot on but when put in the car its off it reads high in idle put a external meter on the coil to read the rpms and it shows about 300 rpms off will put a direct ground wire going to the battery and see what happens

 

[rjc157]

just ran a ground from the tach to the battery and still the same thing ,when I detached the ground wire from the back of the tach nothing different happened shouldn't the needle drop to zero if there is no ground

 

[rjc157]

The only thing I can think of is that the coil is going bad and maybe the condenser

 

[Healey Nut]

The only thing I can think of is that the coil is going bad and maybe the condenser

Try a new condenser set the points , check the dwell angle and try that . Condensers are cheap .

 

[pkmh]

Replacing condenser and or coil sounds good for I had my tach dancing between 3000 to 4000rpm until I replaced those two items (among other things like dealing with the distributor cap and wires, etc.), but I never made that connection or conclusion when the tach's dancing stopped on mine.