The factory tach in my 82 F250 is giving me fits. I am running a MSD 6AL box with Mallory Unilite distributor. Tach used to work - never fully though (sometimes dropping to 0 for a while then working again). Now it doesn't work at all.

I thought it might be loose wire but it wasn't big deal so I didn't bother to troubleshoot right away. Now I want tach working so I've started to trace wires out but so far can not find problem. I have a new factory tach and will install it this weekend but I doubt that is problem since some form of problem has always been there (after MSD installation).

The tack feed comes straight out of the MSD box and is tied into the factory harness at the DG/Y D wire which used to come from the (now removed) factory ignition module.

The truck was EEC-III but is now non-computer. I'm not sure what was going on inside the module as the system needed two wires to feed the tach - I am only using one now.

The wiring diagram shows two wires from tach going into ignition module (BK/LG D shown as IN, and DG/Y D shown as OUT), also shows one wire (R/Y H) from fuse 16 which also feeds seat belt warning light, throttle kicker, and carb solenoid (all gone except seatbelt warning).

I contacted MSD and they sold me a tach filter/adapter but it did not help. MSD says the factory ford in-dash tach should work. Any one else install an MSD ignition with factory tach - and get it to work? The fact that it worked on and off for a while tells me it can be done. What do you think?

Thanks. Mike

 

Same deal with the tach in my '69 Cougar, MSD sold me a adaptor & came up with all sorts of things to do. It's been damn near 4 years & it STILL doesn't work. The have their head completely up their a$$ about this..

 

Sound slike smart marketing. First sell me the ignition module which kills the tach, then they go back and sell me another part to fix what the first one broke. Only problem is the tach adapter doesn't work. Maybe they can sell me a filter to fix the tach adapter.
Does this smell like Microsoft?