Building an Instrument Panel for the Rollback Truck - Part 1

hey guys welcome back our project today is to try to fix this instrument panel on my rollback truck it's at 91 Volvo WG 42 or or white GMC 42 whichever you like so the instrument cluster has had problems for a while now the odometer and all this stuff in this LCD display doesn't work and the speedometer typically doesn't work but other than that the the rest of the panel has been working fine but I'll show you what happens now so you turn the key on and you get the buzzer and you get the seatbelt light and the engine fluid light and as far as I know that seatbelt lights just on the timer it should go out on its own but it's stuck on all the time and then the buzzer should be on right now because the air pressure is low but even when the air pressure is above the threshold the buzzer stays on all the time and then the tach is stuck at like 700 rpm and does nothing the speedometer doesn't even try to work everything else over here on this side is working the voltmeter the water temperature and the oil pressure they must be independently powered because those are all working fine the fuel level gauge also not working correctly but the air pressure gauge is whatever the latest failure is with the instrument cluster had happened while I was on the road so I just popped the fuse out of the fuse panel down here and killed the power to the whole cluster I mean none of the gauges are working anyway so there's no reason to leave it powered up and that buzzer just absolutely drives me crazy so we got to fix it and figure out figure out maybe some of the other problems too if we can get this odometer and speedometer working that would be a good thing I mean speeding is not really an option in this truck but it might be kind of nice to know how many miles we're driving well guys I can't remember where we left off time has gotten away from me this is the main board out of the instrument panel from my rollback truck and I had some video of you know showing this instrument panel not working and you know removing it from the truck I think there's a reasonable chance I may have deleted that so if that's the case let me catch you guys up I've been trying to figure out how to fix this board and I don't think I'm going to be able to so let me show you what happens I'll just power on this board real quick so I don't have the power hooked up to the odometer feed which would cause the buzzer to come on because it's just going to drive us crazy but the important part is that the seatbelt light is on and the engine fluid light is on even though none of the actual sensors are connected to the board and I was looking at the service manual right here you guys probably won't be able to read it but it's telling me this section here is about the tell-tale lamps and it says seatbelt and it's actuated or activated by internal electronics if a new bulb doesn't solve the problem change the main board that's this board and then the engine fluids light so it basically says there's several different switches and sensors that can cause it to come on but basically if the light stays on but the buzzer indicates normal condition and there are no diagnostic messages change to the board well this doesn't have diagnostic messages this is an older truck it doesn't have a data link to the engine computer because there is no engine computer but anyway what it's telling us is that this board internally has a problem and it's causing these lights to be on and this caused and basically causing everything to not work so the board itself is pretty simple but I cannot get anywhere as far as fixing it so it looks like the problem is probably right here this chip it just says Intel 1980 signetics and then there's a bunch of numbers up here it's got to be some kind of a microprocessor chip I can't find any information about it whatsoever none of these numbers right here seem to correspond with anything if I look up this Intel 1980 and signetics it goes to some like 26 50 style micro processors but I can't find a reliable pin out that even tells me what you know what's going on what the power in ground would be or the oscillator or anything like that so I don't know if we're gonna have any luck fixing it and I did trace through the circuit I know for certain that the seatbelt light it's controlled by this transistor which is directly controlled by this pin of this microcontroller so if that's on I think that's a good clue that this microcontroller is is totally not working and I don't think we have any chance of fixing that it probably runs an on board program and that program could be corrupted or whatever even if it's not corrupted we have zero chance of getting it out of there without a pin out so I think we're hooped so I think we're kind of in the in the know when to fold them category here I mean the board it sells pretty simple I think these these switches right here are probably for calibration of the speedometer and the tack and then most of these ICS that you see here are just voltage comparing chips which I probably used to set I don't know various warning lights based on the position of the gauges I don't there's a big you know FET chip here with the heatsink on the back and then a big diode on the front that's associated with that I think that's probably to do with the dimmer for the backlight of the instrument panel that doesn't work either and I haven't been able to figure out what's going on with that this little switch right here supposed to dim the lights that's never worked correctly so yeah I think the problems are just too great we're gonna have to we're gonna have to toss it I can't buy this board it doesn't exist I can't find anybody that will fix it there are companies out there that will fix the data link style but this is just too old so yeah I think we've got to go a different direction you alright let's take a quick look at this microprocessor here with the scope like I said I don't have a pin out so I don't know what's going on but you can see that this pin right here that I know controls the seatbelt light looks like it's being pulled low so it's only like 800 millivolts right now must be low enough below the threshold to pull in that NPN transistor and then what I would assume would be power appears to have 5 volts right there and then I would assume that this is the ground and it appears to be at 0 volts then if I go three pins in we have some kind of a clock type of input or output right here on this pin 12 megahertz so I don't know I couldn't find any data that corresponds to a signetics chip having a 12 micro or a 12 megahertz frequency but maybe it does something else that I'm not aware of so all the other chips are either high or low or sorry so all the other pins are either high or low there's there's no action on any other pin except for you know that one's pretty noisy but yeah this one right here is the only one that has anything significant going on so it's not dead but it just doesn't seem to be doing what it's supposed to be doing and there's you know there's no information about this board it's 30 years old so I think we're on our own so here's the plan I'm gonna buy my way out of this problem I have purchased all new Universal gauges some signal warning lights and a buzzer and various components and we're gonna make an entirely new instrument panel I just don't see any way to save the old one now luckily this is an entirely mechanical engine so there's no reason that we can't just build our own instrument panel and move on with life it's not like we have to communicate with a an engine ECU and you know decode some SAE protocol communication we just hook up some wires and away we go now it's not gonna be super simple because I started making a kind of a diagram here the problem is that there's certain sensors inside of the certain sensors have to turn on the buzzer and some of them are sourcing and some of them are sinking so we'll deal with that part in a minute the gauges are a little bit tricky to come up with some of these are new old stock that I bought off of ebay and the new ones here I bought from Summit they're all video brand and I don't know if they're any better or worse than anybody else's gauges they seem to be made you know various places India China some of them say USA I don't know if they're really made here or not doesn't really matter they're all kind of crazy expensive and the other problem that I have is that almost all of these aftermarket gauges are designed for like hot rods or whatever so every speedometer is a hundred and eighty mile an hour speedometer and every tach is an 8,000 or 10,000 rpm tachometer well let me tell you this Elton Cummins is going 8,000 rpm we got some serious serious problems so I found this company video makes up 3000 rpm tech that'll be just right for us the original ones actually only 2500 rpm maximum and then a hundred and twenty mile an hour speedometer the other thing I wanted was a mechanical oil pressure gauge so that's just a regular old Bourdon tube gauged that uses a line straight out of the engine oil manifold that's what was in there originally and then we're gonna have to change out the water temperature sensor because the new gauge comes with its own its own resistance range so a lot to figure that out I don't think the original one works anyway well the water temperature gauge was never correct and then the fuel pressure gauge is multiple different options on that as far as I can tell from the service information I have the manual that I have says it takes a standard GM 33 to 240 ohm sending unit so that's what I bought and this should work with our existing sending unit and then the other thing that's kind of hard to come up with is we need an air pressure gauge so this truck has a dual system primary and secondary air so this is a dual reading mechanical air pressure gauge so in case you're curious these are all cockpit style gauges from video and you know it doesn't really matter I kind of wanted the tech and the speedometer to be the same and then it would be nice of the other smaller gauges all kind of matched you know aesthetics is very important around here and then as far as the warning lights go I got these from Summit too so I got to turn signal type warning lights you probably can't see that for just a little LEDs and then one of them is like a red one of them's a Czech oil and then I don't know some other various stuff and then I got two little bitty LEDs these are gonna be one's gonna be for my battery warning light and one's gonna be for my low pressure air pressure warning light so hopefully I can pull enough amps through that to turn on the the voltage regulator yes we'll figure that out when we get to it and then this is the buzzer that I've got it's slightly louder and it operates at a slightly more annoying frequency than the old buzzer so I may have to come up with some kind of a muffler to go over it because I didn't want to buy eight different buzzers before I found the right one so I took a big fat guess got pretty close all right guys we're getting back on this instrument panel I can't remember where we left off I wish I could just you know work on one thing and focus on that straight through but it never seems to work out that way anyway this is the new instrument panel right here I had it cut out of a piece of steel this happens to be 14 gauge which is a little bit overkill but it's what they had so we'll take what we can get and basically I traded some some power stroke engine parts to a guy who owns a CNC plasma cutter so I just drew up what I wanted real quick in the CAD program sent him over a DXF file he burned one out it was a little bit wrong that holes were way too small we doctored it up I sent it back over to him and this is what we have and everything looks pretty good I drilled the holes here for the the warning lights using the rotary broach and then there's a couple of small LEDs that are gonna go here and here one for the low air pressure and one for the battery and then just mounting holes on the outside and the original one had countersunk holes for the mounts I'm not gonna do that it doesn't bother me at all if the screw heads stick up above the panel you know it's just an old truck anyway I'm gonna throw this together and we'll talk about wiring [Music] alright guys I think I've got this whole instrument panel pretty well assembled give you a little mini tour of the pretty side so we got a voltmeter water temperature oil pressure speedometer tack fuel level and a dual reading air pressure gauge there's a small LED here that's for your low air pressure warning light a small LED here that's for your battery warning light left turn signal right turn signal this is a warning light here for the low coolant this is a warning light for an air filter restriction and that's a warm eh indicator light for high beams now let's take a look at the scary side yeah that pretty well a rat's nest but takes a lot of wires to make a lot of gauges work and I ran everything down here to a terminal strip and that's how I'm going to connect it to the existing wiring in the truck so let me walk you guys through the wiring real quick this is a wiring diagram that I made and it's just as messy as the actual wiring there's all a few things going on here but basically I split everything out these are the inputs that are coming into the instrument cluster and if you're not familiar with how big trucks are wired it's a little different than cars typically they do not use you know multiple different colors of wire like what you would see in a car typically in trucks almost all the wires are the same color and then they're actually labeled with a number on usually it's printed right on the insulation itself sometimes there's little tags that's more like how we would see it in industrial type equipment so no big deal and I went ahead and labeled all the wires here where they come into the terminal strip and this white thing here is actually the back of the original instrument panel I need it anyway because I need a spacer to make up the correct thickness but it makes a convenient place to mount these terminal strips and relays in the buzzer and stuff these blue and red wires that you see here that's all for the backlighting so in addition to the backlighting each gage also requires a power and a ground that would be controlled by the ignition switch and you'll see it here it's the green and the black wire and all the gauges are hooked up in parallel but the water and fuel level require a actual sense wire the speedometer requires a sense and a ground from the sensor and then the tach just requires a sense input we'll see how that works anyway that part of the wearing is is fairly straightforward alright so the only part of the wiring that's a little bit confusing has to do with the buzzer and that's because the buzzer has four different inputs basically that are required to turn it on so the low air the low coolant the left turn and the right turn so if you're not familiar with these big trucks typically speaking they do not have automatic canceling turn signals at least I can only think of one truck I've ever driven the head automatically canceling turn signals that was a sterling anyway the so the left hand turned and a right hand turn and the hazards will both need to will all need to turn on the buzzer and that's because you know it's so loud in the truck you'll forget to turn them off if you don't have an audible buzzer to remind you and the problem is that the left turn and right turn are sourcing inputs so basically when you turn the right-hand turn signal on you get 12 volts supplied to the cluster whereas with a low air and the low coolant when those sensors or switches are closed they actually short to ground so in order to reconcile the difference in how the switches work I just used a relay so basically what happens here is when the low air or the low coolant switches close it completes the circuit to ground here through the buzzer and the buzzer can can go off now when you turn the right hand or the left hand turn signal that's going to power up the coil of a relay and when the coil powers up it closes in it basically completes a circuit to and so the other tricky part of this is we also need to have a couple of diodes because these switches are hooked up in parallel so what would happen if we didn't have the diode is if the low air pressure switch closed they would turn on the buzzer but it would also back feed through this circuit and it would turn on the warning light for the low coolant so in order to prevent that from happening we use a diode here so that the basically the current can only flow in one direction that way the only way that it can the current can flow through this circuit is if the actual switch is closed same thing with the light the rough left hand the right hand turns so if we didn't have this diode right here blocking the path whenever we turned the right-hand turn signal on it would back feed through this and turn on the right-hand turn single bulb so you know if we were making a few thousand these we just print up a little circuit board use a couple transistors couple of diodes and you know for 10 cents worth of parts we'd have all the functions that we needed but for a single board or a single application like this is cheaper just to buy a relay relays about five bucks and a couple of through-hole diodes wire them up and in the terminal strip right here the buzzer is mounted on the backside here so all in for maybe eight or nine dollars worth of components we can we can build this logic into our circuit and we don't have to have a separate warning buzzer for every function clear as mud yeah so anyway once I get the thing installed and I'm sure that everything works we'll take care of this rat's nest and we'll pull pretty this all up so don't worry about that okay so here's the wiring harness for the old instrument cluster we got plenty of slack here to do whatever we want to do so I try to show you guys can you see this right there where it says 140 that's how the circuit numbers are labeled on the wire they're usually just printed right on the insulation so you see that one says 202 so anyway I'm gonna go ahead and cut these wires right here at these plugs and strip the ones that we need a strip and then we'll just cover the other ones with some shrink wrap and be done with it now don't just go clipping all these wires at the same time because even though the ignition the key is off basically there's a chance one of these wires is hot all righty I think we're all wired in here so these wires here are not gonna be used now I have to make sure that there's not something that gets fed out of the panel you know it's gonna be affected by this but I think looking at the wiring diagram there's nothing it all just comes into the panel and that's it so I think the next step is to fire it up and see what works and what doesn't work and try to avoid an electrical fire and hopefully we'll have a bit of an upgrade over my current instrument panel which looks about like this all right I'm trying to figure out the tachometer here and I don't think it's gonna be compatible with the sensor that I have so it says in the sheet here that it can go up to 25 pulses per revolution and I just took the scope up here to the tach output this is the signal that comes out of it so it's like 880 microseconds between yeah that's the period of the wave here and so like 1.1 kilohertz anyway so I figured if it's 800 rpm at idle that's about 14 revolutions per second so I think if I did the math right it's putting out about 80 pulses per revolution so I don't know if that's gonna work with this with this tech so let me think about that for a minute okay it looks like my alternator does have a tach output and it looks like it's putting out 12 pulses per revolution or 13 pulses per revolution right now so I think that'll work we'll have to run a new wire out to the tach my concern I have is it it's it's full voltage so hopefully this will tack can handle 15 volts in input I think you should all write proof of concept that's my test lead clipped into what I think is the TAC output of the alternator I'm using this 10 foot retractable test lead being a super handy for stuff like this and I've got the other end clipped into the backside of my tech so let's fire up and see what what happens here all right we got something I want to fine-tune it but at least it's working cool and then my my high beam light is wired up wrong and I switch that one around fuel gauge seems to work I haven't looked up the air or the oil pressure voltmeter works battery warning light works low air warning light works my turn signals are working all right guys it's getting late in the day the mosquitoes are starting to move in just makes it miserable to work down here I've had so much flooding that the mosquitoes are just running rampant anyway we've got a few things working and we got a few things to figure out still so I think we can make the tack work off the alternator and the voltmeter is working I think the water temperature gauge is working this truck probably needs a thermostat it never really gets warmed up the fuel gauge is working I'm sure the oil pressure and air pressure gauges will work we're gonna have to figure out the speedometer next time so that maybe a little bit involved and we're going to figure out how to run the wiring down with the alternator for that tack so yeah a few things to do but I think we'll stop here as the end of part 1 and we'll pick it up again in part two and I'll see you guys there

Channel: Watch Wes Work

Views: 52,824

Rating: 4.9781051 out of 5

Keywords: semi, truck, cummins, rollback, instrument, cluster, panel, tachometer, speedometer, gauge, gauges, wiring, buzzer, relay, diode, custom, plasma cutter, schematic, diagram, mechanic

Id: 4605S-0m2t4

Length: 24min 12sec (1452 seconds)

Published: Sat Jun 15 2019