1985 Diesel tachometer

[James1997]

Hey guys! New to the forum but not new to the bullnose style Ford trucks. I grew up in my dad's '86 Bronco and have missed it since the day it was sold. I just recently acquired my own '85 F250 with the 6.9L IDI. I'm beginning the "mild" restoration and wanted to make some small upgrades. I see the engine bay still has the factory harness for the tachometer sensor, but no sensor in the pump housing, and no tach in the dash. I also see my dash cluster does not have the correct electronic board sheet to be compatible with a factory tachometer. Is there any way I can use a factory tach and wire it in to a factory sensor without too much modification? Any help or suggestions would be amazing. Thanks!

[Gary Lewis]

Welcome!  Glad you joined.  

Where's home?  I ask because we have a map (Bullnose Forum/Member's Map in the menu) and we can add you with a city/state or zip.

As for the tach question, here in the NMSH folder isn't the best place to ask as not as many people will see it as if you asked in the main part of the forum.  But if your truck has gauges and not idiot lights then I think you can add a tach fairly easily.  The wiring should be there and if you add the sensor you can plug the harness into it.

But on the tach end you have two choices.  The easiest is to buy the right instrument cluster or just the printed circuit that supports the tach and swap it out.  But since there are only three wires it would be relatively easy to hardwire it yourself.  The connections to the tach are on the studs with which the tach mounts, and they are labeled on the case.  So you can put ring-tongue terminals under the nuts and wire back to the wiring harness.  But I'd put a connector in there as getting everything hooked up in the close confines of the instrument panel might not be fun.  Or make the wires long and be able to connect to the tach and then install the cluster.

[grumpin]

Welcome!

[Ford F834]

Welcome to the group!

As you noticed, 85/86 diesels had the tach option and are wired for it. Adding one is plug and play and can be done in about 30 minutes with no modifications. You need:

-The tach sensor for the IP housing.

-Tach circuit film for the cluster (note that diesel and gas truck circuit films are the same 81-86).

-Tachometer… (note that you need the 4500 rpm 6.9 IDI gauge with the yellow and red zones on the gauge face. Gas engine tachs or diesel tachs from a medium duty truck will not read correctly off of the tooth count signal from the IP gear).

As Gary pointed out a cluster swap + IP gear sensor is easier than adding the film and gauge to your cluster but either will work.

[Gary Lewis]

Thanks, Jonathan!  Very helpful information.