Updated 08/01/11

Analog to Digital Instrument Cluster Conversion

The following is an instructional document on convertinga Blazer/Jimmy/Bravada/s10 pickup/etc. analog instrument cluster tothe digital instrument cluster.

WARNING:

THIS DOCUMENT IS TO BE USED AS A GUIDELINE AND THEAUTHOR

IS NOT RESPONSIBLE FOR THE READERS ACTIONS BASED OFFOF

THIS INFORMATION. Use at your own risk.

GENERAL INFORMATION

Written by Michael Akey ­ Copyright 2004. Revision 5.

This document can be reproduced freely as long as it is kept intact and proper recoginition is given to the original author.

BACKGROUND INFORMATION

Some useful information...

This vehicle used in this document is a 1991 Chevrolet Blazer S­10/Tahoe edition with 4 wheel drive and an automatictransmission.

This guide WILL ONLY WORK FOR 1989­1994 MODELS!* If you have an S­10 Blazer that does not fit into that time period, oris a 1994 S­10 pickup, stop reading now. All S­10 Blazers made in 1988 and earlier use a cable driven speedometer, whereasthe newer models receive an electronic signal from a Vehicle Speed Sensor (VSS). Also, installing a VSS on an older model S­10 Blazer is quite hard, and would require quite a bit of extra wiring, and a small computer unit that interprets the VSS signalcalled a Digital Ratio Adapter Control (DRAC) which is located next to your ECM/PCM.

ALL analog instrument clusters use an 18­pin connector that is located in the lower left (looking from the front) of the cluster.Likewise, all digital instrument clusters use the 34­pin connector in the middle of the back of the cluster. GMC Typhoon/sycloneinstrument clusters are completely different and are not compatible with any other clusters.

* Not all 1994 S­10 Pickups are compatible with 1994 Blazer/Jimmy/Bravada clusters. Some are considered "secondgeneration." Also, certain 87­88 model S­10s used a electronic speedometer and you should check your vehicle to see if it is. If itis, you can perform this swap.

MATERIALS

These are some of the required materials and tools. You may use others at your discresion.

Digital Inustrument Cluster from a comparable vehicle (preferably the same year, and transmission)10mm nut driver and extension rod (extension optional, depending on the type of tool used)9/32inch nut driverPhillips head screw driver34­pin connector (don't forget to get as much wire as possible when removing it from another vehicle)34­pin connector holderWire cuttersNeedle nose pliers (optional)Flat head screw driver (optional)

THE CONNECTORS

The 18­pin connector:

The Pinout:

1 Panel lampinput 10 Anti­Lock indicator

lamp

2 Hot (+12V) 11 Service Engine Soonindicator lamp

3 Generatorindicator lamp 12 Hot (+12V from

generator)4 Upshift 13 DRL indicator5 E. Brake light 14 Speedometer input

6 Coolant temp.input 15 Fasten seat belts lamp

7 right turn signal 16 High­Beam indicatorlamp

8 Fuel sensorinput 17 Ground

9 Oil pressureinput 18 Left turn signal

The 34­pin connector:

CLUSTER REMOVAL

The following are the instructions on how to remove the Instrument Cluster. Remember to store screws in a safe place.

Step 1:Remove the fuse cover panel under the steering column.

Step 2:Remove the bottom plate by taking out the bolt above the gas pedal and the 3 screws holding it on. The 3 screws can beremoved by a flat head screw driver or a 9/32in. nut driver.

Step 3:Remove the 2 screws that hold on the AL/DL connector to the bottom plate.

Step 4:Remove all screws holding on the under steering column trim plate. Don't forget to remove the Parking Brake screw. Also, tofully remove the trim, one must remove the ventilation tube and Parking Brake cable. To remove the Parking Break cable, use aflat head screw driver to compress the spring on the end of the cable and push the lever it is connected to towards the rear ofthe vehicle.

Step 5:Remove the lighting controls plate. Be careful when removing the connectors from the switches ­­ they may break easily.WARNING: light switches ALWAYS have power running to them.

Step 6:Loosen the Air conditioning vacuum hoses.

Step 7:Remove A/C control plate screws.

Step 8:Disconnect the blower switch cable, and grey wires. Then gently pull on the entire assembly until it is about 6 inches out. Thisshould allow plently of space for the next step. If you feel the need to remove the assembly completely, just pop off the clampsholding the temperature selector switch and vacuum hoses. Be careful! Removing the clamps may break the plastic, making itimpossible to reassemble.

Step 9:Remove the 4 bolts that hold on the bezel. (two more nuts on the opposite side; use 10mm nut driver) You may want a"magnetic wand" or some kind to hold on/fetch the bolt so you don't lose it (don't worry, it won't go far anyway.)

Step 10:Pull out bezel and flip to it's side so it is out of the way.

Step 11:Remove the 4 fake nuts that are holding the cluster in.

Step 12:Gently pull cluster out. Remember: Some person down at GM designed the analog guages badly, making it hard to removethem. On the other hand, the digital clusters address the issue of the hard removal, and leave lots of space to deal with. Don'tforget to detach the shifter cable from the steering column if you have an automatic transmission!

Hi­res picture of the analog cluster from the back.

OK! You're done. If you want to put it back together, just perform the removal steps in reverse order!

CONVERSION

NOW WOULD BE A GOOD TIME TO DISCONNECT THE NEGATIVE TERMINAL OF THE BATTERY!

Since most people do not have computers with internet access in their garages, printing out the wiring charts out might be awise idea.

Step 1:After the old cluster is removed and out of the way, unclip the 18­pin connector by pressing in on the 2 tabs (see below)

Step 2a:There are many ways to do this step. This is also the longest and most crucial step, so take your time. Attach the new 34­pinconnector to the old 18­pin connector using the wiring chart below. The method shown in the following pictures is jsut one way todo this. You can just connect all the wires up after clipping off the old 18­pin connector, make a connector (like shown) so youcan revert back to the analog cluster, or how ever you choose. DO NOT REASSEMBLE DASH IMMEDIATELY AFTERCOMPLETING THIS PROCESS.This table shows where the pins on the 34­pin connector connect to the 18­pin connector.

1 6 1822 9 19same as 183 n/a 20n/a

4 see below 21cig. outlet(orange)5 n/a 22n/a

6 17(seebelow) 23n/a

7 7 24178 18 25n/a9 17 26n/a103 27n/a11 14 28n/a128 29never used?131 30not implemented1411 3141512 3213165 33101715 3416

INFO: wire number 21 from the digtal cluster does not need to be hooked up to a constant power source on 91­94 models. 89­90 are required to have this hooked up to an always hot source such as the cig outlet. This is to keep the trip data while your caris off.MORE INFO: Pin 6 is for the dimming of the gauges while your headlights are on. If you don't want them to dim, just ground thewire. If you do want them to dim, wire it into the dark brown wire that goes to your dimmer switch on your lights panel on the leftof the bezel.

Conversion using a middle connector to allow usage of both analog and digital clusters(more time consuming.)

Step 2b:Before the connector can be fully installed, the tachometer must be wired in. To do this, remove the lower panel under the dashon the passenger side. Removing the floor shifter cover will make removing this panel much easier.

Now pull back the carpet as shown, and gently bring down the ECM wiring harness. Look for the white connector taped to theharness. Find the solid white wire going into it. If you had a digital insturment cluster factory installed, this wire would passthrough the connector and go to your instrument cluster. Cut into that wire and use some 16 or 18 gauge wire and route it to theinstrument cluster connector.

Step 3:The next thing to do is to plug in your connector to the digital cluster to make sure it works. Start the car and make sure the tachalso works. Once you have confirmed that everything is in order, continue on. NOTE: When there is no signal to the oil/fuelgauges, they will read as max/full.Example photos:Power On Self TestDisplay on, engine offEngine running

Step 4:To finalize the process, you now have to slide the connector into the plastic connector holder, shown below. Then carefully pushit back into the dash so that the 3 screw holes are behind the plastic of the dash (see below). You may need to remove one ofthe wiring harness clips that occupy the hole where the bottom screw goes. How you attach the plastic holder is up to you, butremember to watch out for the wiring harness. You do NOT want to accidentally put a screw into that ­­ this would cause seriousdamage to your electrical system. I personally when to the hardware store and picked up some new screws and bolts that wereabout a half inch long, and some washers to hold the screws in on the back side.

Step 5:Install the cluster making sure to put the shifter cable through the hole (see below). DO NOT FORCE IT. You may need to re­align the connector so that it fits properly.

Step 6:Check and make sure the cluster works once more, and then take the car our for a spin and make sure the speedometer works.Then put everything back together and you're done! Please feel free to email me with questions using the email at the bottom ofthe page.

FREQUENTLY ASKED QUESTIONS and EXTRA INFORMATION

Where can I get the white connectors you used for an intermediate connector (pictured below step 2a)?

These are Molex connectors, Digi­Key as well as many other electronics parts vendors have them available. (Part on Digi­Key,Molex part number 76650­0071)

What if my digital gauges do not work properly?

I don't repair them ­­ however, other people do (Some are on eBay). Also http://www.mrwhizard.com/ repairs them and will shipto Canada. Please note I have never used their services. Any repairs needed for gauges that I've used or tested were done bymyself. Often times it's just bad solder joints on the power supply daughterboard, or the tubes themselves. I've heard that theVacuum Fluorescent Display drive supply was rather wimpy and would die prematurely, but I have not run into this personally.Thanks for visiting!

Are there different types for different vehicles?

Yes. There are some subtle differences, but are mainly cosmetic:

The idiot lights are not always the same ­ some have a hazard lamp, check fluids, cruise, etc indicators, some havedifferent ones. Most of the ones that changed weren't used anyway.The tachometer came in at least two types: One that red­lines at 5500RPM, and one at 6500RPM. The 5500 is for TBI V6engines, and the 6500 is for CPI V6 engines. They are interchangeable and will work, but you won't have the correct red­line.Early (88 Model Year vehicles) versions require the battery feed to keep trip milage. Later versions do not. They usedifferent mileage chips, early ones I believe were either LSI (or LS?), later ones were rebranded Microchip ICs. I will NOTtell you how to change your milage. DO NOT ASK.

Anything else?

The tachometer is very low resolution. The first 3 bars are wired together, and the higer the scale, it only goes in increments of500RPM. Also, the VFD has "V6" after the word "TACHOMETER," but it was never wired up. The gauges can be modified towork with a V8, and it requires modifying the frequency­to­voltage converter on the blue back­board of the cluster. I have neverneeded to do this, but it's possible.

tester239 [at] comcast d0t net