hey all,my tach quit working due to a blown resistor in the "blob"inside the ignition amp.I tapped into the wire feeding said "blob",added a new 10k ohm resistor and reconnected to the tach. Working now but tach showing about 400rpm low across all rpms Have I tapped into the wrong place, used the wrong resistor or do I need to recalibrate the tach. Any help from electronic wizard appreciated
Thanx
Les
88 1/2XJ-S

 

If so, the guts are nothing more than a GM HEI ignition module (at least that's what it was on mine - '89 V12). I replaced it with a BWD EL 102 from Advance Auto for $23. Swapping is a piece of cake and very self explanatory. The tought part is getting the 4 VERY small bolts off the backside mounting plate that hold on the cover. Good Luck


PS - I have no idea what the ROM calls for (didn't bother to read it , but it seems to work just fine.

 

hey guys,sorry... forgot to update.There is a small white arm on back of tach which zero's the tach(possibly some other function too but I don't know) I tried to upload a pic but firefox freezes every try. Apparently during my fumbling diagnostics it got bumped out of position. After a few tweaks (it's really sensitive) all is well.As an aside I have replaced the ignition module before and it IS a piece of cake.
Thx as usual
Les