Among recent B-platform cars, only the 1996 Impala SS came with a factory tachometer. The 1994-1995 Impalas didn't have a tach and neither did the 1994-1996 Caprice and Caprice 9C1 (police package). You had to go back to the 1991-1993 Caprice LTZ or Caprice 9C1, or 1991-1993 Buick Roadmaster sedan or wagon, or 1991-1992 Olds Custom Cruiser wagon to find a factory tach in the instrument cluster and even in these cars it was a small-style analog tach next to either a digital or analog speedometer. I don't know tach-wise what the Cadillac Fleetwood's had in any year from 1991.

I like having a tach, so I installed an Autometer Autogage, Model 2300, 3-3/4" diameter, black plastic colored and back lighted tach in my '94 9C1. It was around $40 and I got it via Summit. Actually Santa got it for me, and probably ordered thru Summit http://www.summitracing.com.

I originally planned to use a 2.25 inch diameter tach and mount it in the black cluster bezel, but I later decided that Size Does Matter, and that the bezel placement makes it harder to read. So I went with a bigger tach and used a dash pad mounting.

Note: I could have mounted the tach near the driver's side A-pillar, either from the pillar or on the pad itself, but my car still has the 7X6 driver's spot-lamp, so the tach would have interfered with the spot-lamp handle rotation and operation.

Disclaimers - You might want to disconnect the battery.... but I didn't since I didn't think I'd vaporize or destroy anything. I also made sure that any place I installed my tach would not interfere with airbag (SRS) deployment. FYI.

The tach (I used) has 4 wiring connections to make, though I forget the wire colors since I did the install last winter.

The four wires are:

A. ground
B. +12 V power when ignition is ON.
C. +12 V dimmer-controlled power for tach lighting
D. tach signal from the PCM or from coil.

The easiest way to hook this up in a '94-'96 9C1, or in a '94-'95 SS (the '96 SS got a tach in the instrument cluster, the rest didn't), is to do the following.

1. Remove the instrument cluster black bezel trim (2 screws), and move shift lever all the way down to get it out.

2. Remove (carefully) the ashtray. You need a very small flat blade screwdriver to help get the sliders out from the slider detents. The ashtray also has a small light bulb in it, with two wires for power and ground. You will use the ashtray light bulb wires to take care of the ground (item A, using the ashtray black wire) and dimmer controlled lighting (item C, using the ashtray white wire). Carefully disconnect the connector that feeds the ashtray wiring, so you can remove the whole ashtray slider from the dash.

3. Then unscrew the metal brace that the ashtray goes into. Should be 4 screws.

It is possible to install the tach without removing the lower dash, but the tach placement might require it. In my case, I mounted the tach to the top of the dash pad, just to the right of the dash pad cluster bump (if you have a 94-96 Caprice/Impala, you'll know what this is), and in front of the defroster grill. Other mounting locations are possible, but I like the tach where I can easily see it and I didn't mind putting three mounting holes into a dashpad already altered by the police dept that once owned the car.

Also, as viewed from the exterior, the tach *might* resemble a radar unit.... thus adding to the 9C1 motif. I also angled the tach towards the driver location. With this install location, it was useful to remove the lower dash to help run the wires. In hindsight, the ashtray and cluster bezel are probably the only things that need to be removed.

With other install locations (say at or on the cluster bezel), the lower dash probably does not need removal. That said, and using another mounting location, skip ahead to #7.

4. Then remove the rest of the lower dash screws. You need to open the driver's door and unsnap the fuse box door to get to one of them. There is also one hiding behind the glove box door edge. You do not need to remove the glove box door. The rest of the screws are at the base of the lower dash, so you need to feel and/or look for them.

5. There is a plastic cover in front of the driver's knees and is part of the lower dash. It pops out after you remove the lower screws.

6. After all the screws are out, the lower dash pops out by pulling on it firmly. It's scary when you do this the first time, but it's no problem after you get used to it. I later used silicone grease on all the snap-in fittings so that future install and removals are easy.

7. I won't try to explain how to mount the tach -- that's your job to figure out. What you now need to do is deal with the wiring. As stated above, it's extremely useful to disconnect the ashtray lighting and to use it to help wire up the tach. If you look carefully at the light bulb receptacle, it may be deformed from heat stress from the light being on whenever the car's light are on. It doesn't matter that if the ashtray is open or closed - if the parking or headlights are ON, so is the ashtray light. Bad design!

I cut the wires just next to the bulb, so I could use the factory connector (which was disconnected above). I then made a connector (Molex style from Radio Shack) for the tach wires, and a mate to it. I then connected the ash tray wires to the tach (via the connector) as:

- tach ground wire (item A in list above, using ashtray black wire)
- dimmer controlled lighting (item C, using ashtray white wire)

Once you make these connections, try the parking lights (turn them ON) to see if the tach lighting comes on. Then try the dimmer on the dash to see if you can dim the tach lighting. Then shut the lights off.

8. OK, now you need to make two more wire connections, one for hot-in-run +12 V power, used when the ignition is ON, and the other wire for the PCM. First is the hot-in-run connection.

On my '94, there are several locations in the fuse box (next to the driver's door) which have power but are not used on the Caprice/Impala. The one I used for the hot-in-run +12 V to the tach is used for the variable effort steering (VES) in the Buick Roadmaster, but isn't used on the Caprice/Impala carline. Using my FSM, Book 2, I determined that the VES is a hot-in-run source of power, so it is perfect for the tach.

Scott Peitzsch suggested the approach of using unused but handy fuse box power, and steered me to the correct terminals:

"This typically means that your variant of the platform will have unused openings in the fuse box that contain power feeds from both switched and un-switched sources. You can take advantage of these feeds by buying Napa/Belden p/n 784507 (#14 - #16AWG) and p/n 784509 (#18 - #22AWG) terminals and wiring to these unused positions in the fuse box. Place an appropriately sized fuse in the newly wired position and you're in business!"

from his web site at:
http://people.ne.mediaone.net/jlg-sep/scott/functional_mods.htm

I believe the 784509 item is the one that will slide into the fuse box on the upper side of the VES slot. I soldered and crimped the feed wire to the connector, and slid an end-cut long thin tie wrap (per Scott's suggested practice) into the connector. Now that these were together, I blindly slid the other end of the tie wrap into the underside of the fuse box until I had it slid through the correct hole for the VES upper terminal. Simultaneously pulling on the tie from the outside (where I can see the tie and the slot in the fuse box where the tie exits) and pushing (blindly) on the connector from the underside of the dash allowed the connector to snick into place and lock.

Then I just pulled the tie wrap from the connector. Now the VES slot is ready to go, once you connect the feed wire to the appropriate tach wire. I used a 2 A (purple) mini-blade fuse to make the connection in the fuse box itself.

***** Reread this a few times. I'm basically trying to describe a tricky (half-blind) install procedure that requires some patience to get right. *****

9. The last wire to connect is the PCM/Coil wire, and this is the signal from the engine that tells the tach what speed the motor is running at. Instead of writing this up I will attach a few files from Scott Mueller and Kevin Lindsay that handle it. In brief, you run a wire from the tach, thru the firewall rubber plug, along the driver's side fender, and into the PCM. You can also attach it to the coil, but I took the anal route and attached to the unused A13 location on the PCM "A" connector.

10. Lastly (and almost a year after my tach install) I'll add a footnote. The tach works great!

I did find the tach's #194 clear (backlit) bulb too bright, and if I dimmed it with the dash dimmer, the instrument cluster dimmed too much. The solution was to remove the #194 bulb and replaced it with a not-as-bright #161 bulb. That helped but then I went one step further: I got some cheap clear nail polish and added to it a few drops of some hobby modeler's orange paint, so that I could coat the bulb so that it would glow orange. This further reduced the brightness of the bulb, and matched well the orange (red) Pontiac bulbs I had installed in the (backside) of the factory instrument cluster. So now all the instruments glow an orange-ish red, and only the speedometer and odometer glow blue.

Also per Scott Peitzsch's suggestion, I allowed the four wires in the back of the tach to lazily loop out and down into a rubber grommet hole in the dash pad. I made two small electrical tape wraps around the wires and then covered the wires with 1/4-inch size black split loom tubing. It cleans up the dash wiring greatly. I also used plenty of splitloom under the dash to try to keep things tidy.

From: Scott Mueller
Date: Fri, 19 Sep 1997 05:27:38 -0400
Subject: A13 Tach signal

William,

I saw your posting on the listserver re: obtaining tach signal from A13. But...where is A13? My PCM has color codes: red, blue, etc. at the connectors.

Here is the translation for the PCM connectors:

Color '94/'95 '96
-------------------
   Red     A     C1
Black     B     C2
Grey     C     C3
Blue     D     C4

In the '94-'95 manual the Red, Black, Grey and Blue connectors are referred to as connectors A, B, C, and D respectively, while in the '96 service manual they are C1, C2, C3 and C4. The tach signal is on pin A13 according to the '94-'95 manual designation, and C1-13 according to the '96 service manual designation. Both are really the same pin 13 on the same red PCM connector, only the designations were changed in the manuals. Scott.

From: Kevin Lindsay
Date: Sat, 29 Nov 1997 16:46:15 -0800
Subject: RE: Which PCM wire for tach. signal?

>Which wire would be the best signal to an aftermarket tachometer?

PCM pin A13 (undocumented in B body service manual)

Kevin Lindsay Garden Grove CA
SoCalSS President and Founder (370 owners of 94-96 Impala SS's)
95 Black SS 5,367of 18,365 (BLK95SS) Built 12/23/94 Signed by Jon Moss
97 Black C5 4,484 of 9,752 6spd (BLK97) Built 4/25/97 Signed by Dave Hill

From: Scott Mueller
Date: Sat, 29 Nov 1997 22:24:33 -0500
Subject: Tach signals... -- TACHSIG.TXT

Impala SS Tachometer Wiring:

The best place to get a clean (filtered) noise free tach signal would be from the PCM connector pin A13. All B/F-car PCMs output the tach signal on this pin. You will need a terminal p/n 12084913 (for 20 ga. wire) to install in the PCM A connector, and then run the wire (the factory uses a white wire for this application and if you are diseased like I am the correct color is important <g>) over to the oval plug in the firewall behind the LH wheel well. I removed this plug, slit it up from the bottom, ran the wire through it, and re-installed the plug back in the firewall for a water tight seal. Now you have a clean tach signal for any tach you might want to install.

In the '94-'95 manual the Red, Black, Grey and Blue connectors are referred to as connectors A, B, C, and D respectively, while in the '96 service manual they are C1, C2, C3 and C4. The tach signal is on pin A13 according to the '94-'95 manual designation, and C1-13 according to the '96 service manual designation. Both are really the same pin 13 on the same red PCM connector, only the designations were changed in the manuals.

Here is the translation for the PCM connectors:

Color '94/'95 '96
-------------------
   Red     A     C1
Black     B     C2
Grey     C     C3
Blue     D     C4

An alternative to the PCM connection would be to use the negative coil signal. On a '94 or '95 Impala, there are three wires at the coil, two in a grey connector (pink/black and white/black), and one in a black connector (pink). The negative coil connection for a tach is available in two places. One would be the spare unused terminal location in the black connector (this is what I actually used when I originally installed my tach). The other is the white/black wire in the grey connector. The spare terminal in the black connector and the white/black wire are connected together inside the coil, so they represent the same signal, which is the
negative side of the coil.

Note that '96 Impalas use an improved coil with more spark energy and a different connector with only two wires (although there are three terminals in the coil, only two have wires connected to them). In the '96 models the two wires to the coil are pink/black and dark green. The dark green wire is the negative side of the coil, and could be used to run a tach.

Of course the '96 Impalas already have a tach running off of the A13 pin on the PCM. Unfortunately this signal is 1/2x the normal tach signal for a standard V8 tachometer, which will cause the tach in the Camaro cluster to read rpmx1/2 or half speed. Likewise if you run the F-car PCM calibration in a '96 Impala, the factory tach will read rpmx2 or double speed.

I am using the PCM signal to run the factory tach in my Camaro instrument cluster. Note that at least for '94 and '95 Impalas, this works the same whether I am running the B-car or F-car PCMs, as I have done it with both. If you are installing a Camaro instrument cluster in a '96 Impala, then you should use the coil signal to run the tach. If you are installing both a Camaro instrument cluster AND an F-car (Camaro) PCM in a '96 Impala, then the factory PCM tach signal can be used.

Finally, note that ALL Impalas have the tach signal available at PCM terminal A13.