Tach Install ?

[mconstable]

Hello all, a buddy of mine has a 1st Gen. and wants to install a tach.

Can anyone give me tips, or point me to a website that explains it.

 

[Prairie Dog]

You may want to ask this in the first gen forum. I know there was a connector under the dash of my 93 that even included panel lighting but I forget the details.

 

[DBF]

If your friend's truck is a 88-91, stop reading now.



The 1992 & 1993 First-Gens were factory-equipped with a plug for a tach. ISSPRO makes a mating connector kit (R8912-92, works on both years) that you can then plug their R8503 tach into.



Download the catalog from ISSPRO's web site (www.isspro.com), then look in it for oil temp gages, etc.



The truck's plug is located just to the left of the steering column under the dash, usually taped to a large wire-run. It's flat with four female positions.



DBF

 

[cumminswillie]

alt tach

I have three of the first gen. dodges and 1 of the second. Auto meter and several other companies offer a tach that works off of your alternator. sounds goofy but it works. you just have to calibrate it once and your good to go

 

[mconstable]

Thanks Guys!!

 

[Sri Ram]

DBF, You seem to know about this…Where does the factory tach plug-in get its signal, from the front or rear of the engine? Also, it's been said in this forum that some 91. 5's had the factory plug-in. Is this true? thanks.

 

[MeritBadge]

If you have the tachometer provision it will be inside the cab. It is a flat 1x4 connector that comes out of the main harness. If you look up under the dash you will see the large black square mutipin connector. A couple inches back you will see this tach connector come out of it, which is also only a couple of inches long. The wire colors are black, orange, black, and gray. If you have this connector the easiest thing to do is to order a tach from Isspro. The R8503 for 0-4000 rpm or R8501 for 0-3000 rpm. Along with the wire harness R8912-92. The harness comes with instructions, which makes it even easier.



If you don’t have the connector (89-91. 5) you can order a tach and R8912, which is a magnet sensor kit. You have to glue the 2 magnets on the balancer and bolt the sensor on using one of the oil pan bolts. This also comes with directions from Isspro.



I recommend using Isspro for a tach install. It’s easy, accurate, you don’t have to do any calibrating, and you can order everything off their website. I have the directions/illustrations from Isspro for both of these tach setups if you need em.



Merit

 

[DBF]

Where does the factory tach plug-in get its signal, from the front or rear of the engine? Also, it's been said in this forum that some 91. 5's had the factory plug-in. Is this true? thanks.

Tach plug gets it's signal from the SBEC (Single-Board Engine Computer) on the gray wire. IIRC, it's a square-wave with pulse length proportional to rpm. Red is power when running. The other two are ground and power to the lamp in the tach (I think lamp power is black ).



How the SBEC generates the tach signal is a mystery to me. Maybe off the crank position sensor vs. time?



I don't know if the 91. 5's have it. I have a 92 and the 92 Service Manual (Tach connector shown on upper right of Sheet AD52 on page 8W-95).



DBF

 

[Sri Ram]

Thanks, guys. I'll look for the connector. I've looked in my 91 manual and the 91. 5 update, so far with no luck. I'll try the page you mentioned, DBF. I should have the ISSPRO R8503 tach today.