moonies to needles & DRAC

[TalkingHead]

I swapped my moonies for a needle cluster w/ tach from a '94 'burban.


After reading through the writeup on this swap in the tech articles section located here:

http://www.fullsizechevy.com/forum/general-discussion/tech-articles/69806-update-94-gauges-w-tach-27.html

I attempted to swap the cluster plugs... This was not as easy as I expected since my harness had a few wires with different colors other than that which was listed in the writeup. So, after quite a bit of trial and error I played around with swapping different wires I thought might be causing my problems.

The gas gauge was pointing in the 3 o' clock position (way past the FULL mark) , I fixed that by figuring out that the wire for the gas gauge is purple instead of pink like the diagram shows.

There were several brown wires coming FROM the dash (three if I remember correctly) and I had to guess which one went where. Again played around with that some and I think I finally attached the wires there correctly.

Everything seems to work in the cluster, All gauges, Idiot lights, turns, SES, high-beams etc. But here's the issue I'm having: every once in a while the speedo needle jumps from wherever it was, to somewhere much higher, then settles back down to the speed you are actually traveling at. This all happens very quickly I might add, but it is something I have witnessed several times at random.

Could my DRAC be goofy or screwed up? All the wiring connections are soldered joints so there shouldn't be a problem there. Since the instrument cluster usually works like normal, this leads me to believe my wiring is good-to-go, and that the issue must lie elsewhere....

Thoughts? Input? Advice? Paper? Plastic?

[TalkingHead]

No one knows anything on this?

[TalkingHead]

bump

[VenomousGT]

im sorry to thread hujack but you may have the answer to my question im stuck on... what color was your speedo wire.. my schematic says blu/blk but i dont have that wire. Im doing this same swap, maybe if mine gets done I can verify if I have the same issue as you, but as of now i have no speedo.

again sorry, and thanks in advance

[TalkingHead]

No need to apologize for the thread jack. At least somebody bothered to f'in post!!!

Are you talking about the speedo wire coming FROM the dash??? If so, mine was yellow so I would think yours should also be yellow. There are usually two yellow wires coming from the dash, one is for speedo and other is for the seat-belt-idiot-light.

I have a couple wiring diagrams that I used for the cluster swap. Let me know if you want them I can share them, although I have to boot to the other side of my hard drive to access them, no biggie.

And I think the issue with my speedo needle going crazy is just something bad with the cluster itself, a bad or intermittent ground somewhere within the cluster itself. I've talked to other people who have had similar issues and the consensus seems to be internal electrical issues with the cluster itself.

[VenomousGT]

anything you can provide with ease to help me out would be amazing! ive got everything working in the dash except my speedo.. i thought i tried the yellow wire and didnt get any speed change ill run back out now and check and try it again.. is there any way to test that wire? should it produce ac voltage or dc voltage with the speed change?

[VenomousGT]

i just ran out with much enthasium and checked my harness.. i have 1 yellow wire coming from the stock gauge harness that plugged into the stock cluster.. i had tested that wire yesterday and showed a small ac voltage increase with speed... i hooked it up with no luck. I tried it again just now and still no luck on my speedo... do you know if it checks speed off the front or rear wheels? i have the truck on jack stands and have been letting it freespin with the back end in the air running about 10 mph but the speedo isnt showing anything.. i wonder if I should take it down the road and try it.

edit: ran down the road with no luck... oil press is fine, coolant gauge is fine.. my voltage is a little weird, it doesnt seem to move any when my voltage changes and my fuel gauge seems to jump around a bit as well.

[TalkingHead]

Only one yellow wire, Hmm... How significant was the voltage increase on the yellow wire?

The VSS (Vehicle Speed Sensor) feeds the speedo. There is a reluctor wheel inside the transmission with a magnetic pickup aimed at it. As the VSS reluctor rotates with the transmission output shaft, it generates an AC signal which is converted into a calibrated DC signal by the DRAC/VSSB. Finally, this calibrated DC signal is fed to the speedometer, PCM, ABS etc. etc. etc.

I suggest checking your wires for the DRAC, and possibly trying another DRAC altogether to see if maybe it went bad.

Also, note on the wiring diagram "low speed signal" and "high speed signal". Definitely check those wires as well because they are from the VSS.

EDIT: Someone in their infinite wisdom has forum settings preventing me from uploading the wiring diagram that I have. If you want the wiring diagram tell me your email and I'll send it to you.

[VenomousGT]

i think you just answered my question and I didnt even realize it... the DRAC is built into the stock gauges.. it should be a separate module on my 98 suburban i took all my stuff out of... with that being said, i havent done that because I wasnt sure that was needed... I just have to find where its located on this burb so I can take it off.. then gotta figure out the wiring for it too.

my email is venomoussvt@gmail.com

and again, thank you very much for your help on this!!!

[VenomousGT]

ok.... so, i just traced the green speed wire on the harness i cut off for the 98 gauges. I traced it to a plug in the passenger side behind the glovebox. Following the plug takes the wire out to the engine compartment where I lose it in the engine harness. Sooo... im not seeing a DRAC on this truck which makes me think that the 98 gauges do not use a drac, but they may use a different speed sensor which gives a different output. I did get a variable voltage on my yellow wire when I did my test runs on jackstands but I cannot remember how great the voltage was. I know the stock gauges worked flawlessly the minutes before I started this swap so Im thinking either the 98 gauges are the issue and I need some 94 gauges... OR I gotta find some way to give it a speed signal it can use

[TalkingHead]

Yes, on the old style gauges, (moonies) the DRAC is built into the cluster itself, unlike the later clusters where it became a stand alone unit.

I didn't know you were trying to use 98 gauges in a truck I'm going to guess is either a 90 or 91….. The wiring might be different; I honestly don't know as I put '94/'95 gauges in my '90…. Might be a different ballgame trying to use even newer gauges, even though they're still from an OBS.

If it were me, I'd pick up a set of gauges from the yard for a 94/95 truck, most of the information out there on swapping gauges pertains to that particular swap…

I was going to email you the wiring diagrams I have, BUT, they are for using the 94/95 style gauges, not the later '98 style like you're attempting to do. Anyways I can send those diagrams to you if you still want them, but I found these diagrams for the later style gauges that you're trying to use.

Scroll down to the 67th post in this thread:
http://www.gmfullsize.com/forum/showthread.php?t=46559&page=7

[VenomousGT]

yeah ive tried to see whether there was any major differences in the newer gauges.. i was looking for a 94-95 to 98 style conversion to see if i could fill in the blanks.. im thinking the 98 gauges get their signal directly from the computer as its not the same as the tbi trucks..

[VenomousGT]

i just looked at your link and i think those 2 pictures are exactly what im needing.. i am no stranger to wiring, but without the information on the wires I cant fill in the blanks.. I think once I get a 94 DRAC ill be able to complete this wiring!! Hopefully I'll be able to snatch one up this week.. gonna start looking first thing tomorrow.. thanks a ton for your help man, i cant tell you how much you've helped!

[TalkingHead]

No problem :D

Yeah wiring diagrams definitely help for somethin like this.

Make sure to post pics once you figure it out.


Here's a shot of my '94/'95 gauges.
https://sphotos-a.xx.fbcdn.net/hphotos-snc7/s720x720/484115_10100749192843502_632049553_n.jpg


Let me know if you have trouble finding a useable DRAC, I've got some extras :smokin:

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/185823_10100749165518262_325472193_n.jpg

[VenomousGT]

im fighting a charging problem now.. the truck won't charge with the moonies not installed.. until i can find a fix I cant move forward with the truck :(

[TalkingHead]

I wouldn't think that the gauges had anything to do with your charging problem. Don't give up, hang in there, you'll conquer it.