Printable View
I have searched a bunch and can't find out what color wire (s) need to be hooked up from the inst cluster to make the speedo/odometer/trip to work. This is the last piece of the puzzle so if anyboby out there got their 1990 speedo working I'd love to know how. I have a designated wire coming from my pcm thats labeled speedo and it needs a home!! Thanks.
You could pull the cluster apart. Comes apart easy enough if i remember correctly; Follow the ol skool circuit board trace and temporarily make a connection.
Or just wait until someone replies lol.
I used to know but forget after inhaling too much race fuel.
here's a quote from my thread that chevy-art told meQuote:
Originally Posted by exboatracer
For the speedometer to work I used the wires what come from the VSS on the transmission, they disconnect from the rear of the trans and go into the cab. The colors are HI 400 Yellow and LOW 401 Purple.
maybe this will help you
I found those yellow & purple wires(also a ppl/wht wire). I even labeled them "old trans wires" and capped them off & tucked them in my harness coming from c-100. They must have been a 3 wire plug. Anyway I connected the speedo wire coming from my pcm to the yellow & purple wires as chevy-art said and I still have no speedo. Not saying chevy-art is wrong,cause it worked for him. I must be doing something bass ackwards. Might have to pull the cluster like farmtruc said. Thanks. Still scratching my head!
I'm starting to think that maybe my speed sensor is bad. I also saved another plug that came from the old 700r4 trans that is a 2 wire plug, one wire is tan and one is purple with a white tracer. Does that plug ring a bell for anyone. Thanks again.Sorry to be a pita.
Do you have tuning software?If you have a speed reading in you tuning software then the sensor is good.Something may have to be changed in the pcm so you get a reading.You also have to make sure the yellow and purple wires are connected to your pcm so the computer gets a reading.
GREEN WIRE: PIN 20 in the RED Connector (VSS)
PURPLE WIRE: PIN 21 in the RED Connector (VSS)
YELLOW WIRE: PIN 50 in the RED Connector (speedometer)
On my truck a 1992 5 speed manual the wires from the trans sensor green/bk and purple/white went to pins 20 ans 21 on red connector to pcm.I have 1999 gmc pcm and wiring harness.Pin 50 red connector went to speedometer.
No, I dont have any kind of test equip of that sort. Here's what I found,in the red connector,I have a grn/blk wire in pin 20,a solid purple wire in pin 21, and a grn/wht wire in pin 50 that is labeled speedo. The speedo wire was left out of the harness intentionally for me to hook up.This wire-the grn/wht from pin 50 is the one I'm trying to hook up to the yellow and purple wires thats coming from c-100 in my truck's original wiring. Is this ok so far? Thanks for the help gag.
I ended up using the dark green/white wire from pin 50 of the red connector and ran it right to the speedometer. I undid the guage cluster, pulled out the light blue/black wire that is in position S on the plug feeding the instrument cluster. I then cut the light blue/black wire that was in position S and soldered the dark green/white wire to the end of the wire so as to reuse the little connector and then reinstalled the wire back into position S on the plug. Voila, speedo worked.
Hopefully, your wiring harness is similar. I'm using a 1993 wiring diagram from a Chevrolet C/K service manual.
Do you have cruise control? If so, it's a slightly different setup.
Let us know how you make out.
Do you have pins 20 and 21 connected to the vss in your tranny?If not you will not get a reading on pin 50 .I connected pin 50 to the speedometer wire that came out of my drac box behind the glove box.I think the 1990 has a different setup.
Here is some good write ups that my help you out
http://www.ls1truck.com/forums/lsx-t...-wiring-4.html
http://www.ls1truck.com/forums/lsx-t...gmc-k1500.html
http://www.ls1truck.com/forums/lsx-t...eter-help.html
http://www.ls1truck.com/forums/lsx-t...eedometer.html
http://www.ls1truck.com/forums/lsx-t...eter-help.html
You guys are too kind,flooding me with all this good info. The first thing I'll do is check to see if pins 20 & 21 go to the vss plug and then move on from there. With all this help I know I'll get it working. Might take a day or two and I will let you know. Thanks again.
Yes, my VSS wires go to the PCM. Without it, the PCM doesn't have any referencing speed signal coming from the vehicle. I also have the DRAC box behind the glove box and ended up jumping the wire from the Cruise control right to the speedometer wire, thus bypassing the DRAC box. I was having Cruise control issues and it ended up being the '99 cruise control box that I got from the Silverado 6.0 donor vehicle was junk. I just ended up using my '93 cruise control box and switched out the cable from the '99 box so it would reach the throttle/air valve at the front of the engine.
I checked and pin 20 & 21 from the pcm are routed to the vss, so at least that part is confirmed. Still not working though. Some guys say it can be done but they dont remember,maybe something will jog their memory. The truck runs great,lots of power and a blast to drive so this speedo thing is not a big crisis when you look at the big picture,but it would be nice if it worked.
On my 1994 model, I pulled out the cluster , then pulled the plug that goes into the back of the cluster out from the dash as much as I could, on mine there was 1 wire that came from the DRAC box to the speedo , I clipped that wire and connected it to the wire coming from my harness. I used a stand alone from Nelson, they had the speedo wire labeled on my new harness.. This is the easiest way by pass all the other OEM stuff on the truck IMO
The Speedometer wire on the plug that goes directly into the harness is LT Blue/Black on my schematic for a 94 model
I also have a Nelson harness and they left me a green and white wire labeled speedo coming from pin#50 on the pcm for me to hook up. Mickeymotormount also mentioned a lt blue and black wire on his 1993 truck so I'll have to pull the cluster and try that. I'm not sure about the drac box that everyone talks about,hell,I dont even know what it is (lol), but I'm not quitting! Thanks.
By finding the wire on the cluster plug you are bypassing everything and going straight to the speedometer...
Ok,I pulled the cluster and don't have a blu/wht wire.Didn't think there was one cause I couldn't find one on the schematic. After lots of research (homework you guys gave me lol) I found out that the 1990 trucks dont have the white drac box with the blu/wht wire. It's built into the cluster making the hookup more involved requiring a dakoda digital module or a high dollar reluctor wheel from s&p.Here's what I'm doing--- putting an aftermarket electric speedo from Speedway motors P/n91065051 in place of the stock speedo head which will just unplug from the cluster. I'll make a brushed aluminum face plate and mount the 3 3/8 guage dead center. The body of the guage is 1.6" deep so it will clear the circut board. I like the looks of the guage and also the fact that it will give the dash a different look. Just want to give all who helped me on this,and with my build in general a BIG thankyou. I'd like to shake your hands someday.
Thats good to know as my future project is a 89 rcsb, but i was already thinking of going with Autometer gauges since my bro already pulled out the stock cluster.
Just an fyi on the speedway motors speedo. I got mine today and it will not fit as easy as I described in the above post.I will make it work with some cutting and slicing. The spec sheet on the ad says the speedo body is 1.6" deep which is correct, but the mounting studs and backlight make it around 2 3/4" deep. Sorry for the bad info, I should have installed it before I said anything.
Can't you update to a later guage package? I have a couple that I'm not using and would be glad to help out. They're out of a 94 model with factory tach. It may be alot easier than hacking up your dash.
I'm sure there are differences in the wiring, but nothing too complicated.
Thanks for your kind offer to help out.Your idea is probably the way to go,but now I have this speedo and want to make this work.I have a spare cluster on my bench and I'm trimming some plastic so the new speedo will set down a bit more and clear everything. Thanks again.
Post a pic when your done I am doing the same swap in same year truck.
Do you have the part number for the dakota digital module to run the 2002 4l60e trans with the 89 stock cluster?Quote:
Originally Posted by exboatracer
seems like there should be a was to use the 1990 speedo work,Im trying to get one going myself,could I just use a cluster from a 1992 c1500 with out rewiring?
I spent a lot of time on my speedometer cluster when installing the LS1 in my 1988 RCSB. Here is the info on 88-91 speedometers, the cluster has circuits inside that perform the same functions of the DRAC in 92 and later trucks. As in, speedometer driver, speedometer correction, RWAL (antilock brakes), cruise control output, speedometer out to ECM.
88-91 the Yellow and Purple twisted pair wires come off the trans tail VSS and go up the firewall and into large square firewall connector harness near power brake booster. These wires go through connector in firewall and straight into speedometer cluster. The signal the VSS produces is a simple AC square wave signal, the VSS is a magnet reading a toothed ring with 40 teeth, and that 40 pulse signal is what your speedometer needs to work. 88-91 speedometer clusters then condition the VSS raw signal and send it out to everything else, antilock brakes, cruise, original ECM.
If you are using an automatic trans in your swap just jumper off the VSS wires, at trans, at back of speedometer, it doesn't matter, and run them to your new ecm. I don't know why you would though, usually all your new ECM needs to know is if you are moving or stopped. The speedometer output from back of cluster that went to old ECM can be run to new ECM speedometer input pin. Your new ECM is not controlling cruise, antilock brake, or speedometer, as those functions are retained in original cluster if you uncap the yellow and purple wire and run them back up to firewall connector, twist the as they were originally to suppress any noise.
This was a popular swap back when everyone wanted to get rid of their moonie gauges. It does require the cluster connector and pigtail from a 92 or newer truck, cutting the pocket that the cluster fits into, and repining a few wires at rear of cluster. And also, make sure to grab that DRAC module from the 92 because all the functions that are in the 88-91 cluster will now be in the DRAC module, speedometer correction included.Quote:
Originally Posted by pmcarbuilder
You will still have an 85MPH speedo and 5000RPM tach when finished.
1988 VSS wiring diagram- brown/ white turns to brown through a connector