Tach problem with MSD 6AL

[CHA914]

I have read the previous posts dealing with this topic, but none described the same problem that I am having.

I have a new 914 VDO factory tach, with the MSD 6al unit, and the msd tach adapter installed. Currently the tach is reading about 1000 rpm high at all rpm ranges and once the car warms up if I rev the engine above 4000rpm (on the tach, ~3000 real rpm) the needle will drop down to ~1900 and stay there till I go below 4000rpm. So in this state the tach is not much help. However, since the car was purchased with the msd unit already installed, I havn't had the chance to thoroughly check the wiring job. I did install the new tach (blew out the old one being stupid - don't ask) and I also put in the tach adapter.

I will re-check the wiring job, but was wondering if anyone else has experienced this specific problem.

Thanks for the help,

Tony '74 2.0L

[John Rogers]

I am assuming the engine actually revs okay and you have verified the tach readings with a good timming light/tach? If you go to MSD's website they have the diagrams of how to hook things up and double check to make sure that all the connections are tight and clean with no loose crimps. If you have trouble I can check the connections on my 914 to give you a reference.

[CHA914]

Yea, the engine revs great, I have verified that with a timing light and two seperate tachs...one being a recent VDO tach that I have on my vw van.

I won't be able to verify my connections till after christmas...I am assuming that you have never heard of this problem...I guess it must be some kind of an overload signal being sent when the car is revving over 3 grand...