Mustang Owners Club Australia Forum

Technical & General Discussion Area => Tech Torque Pre 1973 => Topic started by: John&Mustang on June 22, 2021, 08:37:19 pm

Title: Tacho not working
Post by: John&Mustang on June 22, 2021, 08:37:19 pm

Hi everyone, I'm new to this forum and suspect this question has been asked long before me. I have a 1971 Mach1 with a boss 351c with a MSD ignition which includes a 6al ignition box, a MSD Blaster SS coil and a MSD distributor. Which all runs sweet as. The previous owner did all this work but the tacho has never worked he told me. As a result he put in a after market tach which works with a MSD 8920 tach adapter. I've disconnected this to try the original tach but it doesn't work as he previously said. Other forums suggest that it needs the 8910 model tach adapter to make it work. Any suggestions please.

Title: Re: Tacho not working
Post by: jiffy on June 22, 2021, 09:35:52 pm

Yup - tach adapter required.

Title: Re: Tacho not working
Post by: LeglessOne on June 23, 2021, 11:49:04 am

Hi John

The 8920 should work ( I have the same one on my 460 - 73 Mach 1)- maybe the wiring needs to be checked.

Here's a link to the wiring pdf https://documents.holley.com/8920.pdf

Shane

Title: Re: Tacho not working
Post by: John&Mustang on June 23, 2021, 08:01:08 pm

Hi Shane, thanks for your reply. But to clarify the diagramme, what side of the tacho plug does the violet trigger wire connect to. The green/red wire on the car or the brown wire? Also the same question applys to the swiched 12v wire.

Title: Re: Tacho not working
Post by: LeglessOne on June 25, 2021, 06:01:26 pm

Hi John will have a look on Sunday and get back to you - I cant remember off the top of my head.