RPM working on Dash but not on logger

[colinp]

Hi I have My RPM connected to the coil on a ford pinto, connected straight to the dash it works 100% perfect

if i then change it so that i disconect the wire from the dash and put it into the DL1 logger change the dash to look at rs232 i get rpm but only upto about 3k rpm then it jumps all over the place?

any ideas?

Cheers

[Support]

Do you have any kind of interface circuit between the coil connection and the DASH input? Which model of DASH are you using? The DASH2 is not designed to have a connection directly to the low tension side of the coil and it could potentially cause damage.
When connecting to the data logger are you connecting to the high or low level RPM input?

Martin