I will be posting pics and info on the two day quest of installing a tach... This will be somewhat long and maybe a lost cause..

If anyone has any info on the signal pulse from pin 48 on the computer module PLEASE LET ME KNOW. I have found that the signal from here is not a square wave pulse but a sawtooth with an amplitude of 7.85 to 8.42 volts and a duration of 2 milliseconds, with an interval of 3.5 milliseconds. Talking to Auto Meter techs they say they need a square wave and close to 12 volts... I have not bought a tach yet using O'scope, multimeters and freq. counters... This applies to F150 xl 2000 and above.. WIll get back later with more info...

 

Here are the PICS..

Disconnect negative from battery. Then loosen 10 mm bolt from connector and relase tabs from black cap.

 

Step two.
The connector cover plate has two tabs holding it in place (fig. 1)

 

Step 3.
After removing plate (fig. 3) then turn connector over and use #34 drill bit and drill the plastic pin on #48 the pins are marked on the inlet (wiring side of the connector

 

The sleeve pins will be exposed and now solder a sleeve onto 14 feet of #20 gauge wire I used (fig. 6) Radio Shack Cat. # 276-1428A D-Sub connector for the pin sleeve. After soldering use shrink tubing to cover sleeve. The total length of shrink tubing and sleeve about 5/8 of an inch. Make sure to test the length of the pin sleeve so that it is almost flush with front of the connector.

 

Now feed wire through front of connector an align sleeve (fig. 4) snap cover plate and black cap and install connector back on.
I know this not very clear but I will try to answer any questions

 

I came across this gizmo in MM&FF: http://www.paulshp.com/paulshp.htm - follow the mustang link. It lets you use a tach with the distributorless ignition. It's not cheap though.

Ian

ps - MMFF says this is the only way to get it to work but hey, they've been wrong before!

 

WFstewart,,, you are saying that all you have to do is make a connection to the computer on # 48 pin??????? is it really that easy or do you still have to buy that damn interface module that is like 300 bucks?? Thanks..... JJ

 

I am saying that It is not that easy. I am trying to get a newer version of an Auto Meter Electronic tach to test with.
I think ford has stop allowing aftermarket hookups of Tachs, etc. to their computer. I know that a new cluster panel with a tach is not the only part you have to buy. There is a firmware flash! So if that is true then how do they get the signal to the new cluster if no wire is present on pin 48 of the computer. My guess is that it is handled by the communications port to the cluster and that Ford has made sure that there is not a usable signal available. I wish a Ford tech would email me about this.(hint,hint)
One can make an interface that would not void warranty, it would have to be optic-coupled then have a pulse-stretching mono circuit added. This can be done! What I need is the signal requirements from Auto Meter on what is the min. voltage, the length of the square wave pulse and interval that their tachs require.

On the previous post about Paul's HI-Perf..... I knew about this and $300.00 seems a bit high to me. But it may be more work then I expect.

On another note. Are the HELMS manuals (E.G. Electrical) any good and do they offer detailed info on the computer connections.