Dim Dash Lighting

[cmroles]

Today while tinkering around with my M1009 I decided to do a little investigation into the dim backlighting for the gauges. The light bulbs all work, but seem to be fairly dim....to the point where its difficult to read the speedometer at night.

I pulled out the instrument cluster face and removed the bulb socket for the Voltmeter. I then connected my multi-meter to the contacts in the socket and measured the voltage while turning the dash dimmer through its range.

1. The dash dimmer starts out at 0VDC as expected when the switch is all the way clockwise (dash lights off / circuit "open")

2. As the switch is rotated counter-clockwise it begins to read 8.5VDC (dash lights on but all the way dim)

3. As I continue rotating counter-clockwise the voltage climbs to a maximum of ~10.8VDC (switch rotated all the way counter-clockwise)

Now, this should be a 12V circuit, but it seems to max out at 10.8VDC. This looks to me like its falling about 1.2V short of its full potential. Since the difference between minimum / maximum brightness is only 2.3V (8.5V - 10.8V) this could possibly be a significant loss of lighting ability.

My suspician is that the headlight switch / dash dimmer is the problem. The dash dimmer is probably nothing more than a variable resistor, and is not going fully "short" when its rotated to the stop.

Has anyone else done this same test, and if so, what did the results look like? I am almost tempted to jump the wires to the dash dimmer straight across to see if the increase to a full 12V makes a big difference.

 

[IdahoPlowboy]

I have tried 3 different switches and have the same dim dash lights with them. I have not found a way to fix this yet.

 

[cmroles]

I have tried 3 different switches and have the same dim dash lights with them. I have not found a way to fix this yet.

Did you ever happen to measure voltage across the switch? I am intrigued by the "missing" 1.2VDC at the bulb socket...but I could just be chasing shadows...

 

[Gottlos]

You could try swapping the illumination bulbs for LEDs. Someone else on this site painted the inside of the cluster with (racial identifier) chrome spray paint. Just don't swap in LEDs for the GEN lights. They are part of the circuit apparently. I did and ended up rebuilding both alternators thinking there was a problem. I also used RED LEDs. Kinda gives the gauges a "tactical" look. I don't have pictures to post, but it looks pretty cool.

 

[cmroles]

You could try swapping the illumination bulbs for LEDs. Someone else on this site painted the inside of the cluster with (racial identifier) chrome spray paint. Just don't swap in LEDs for the GEN lights. They are part of the circuit apparently. I did and ended up rebuilding both alternators thinking there was a problem. I also used RED LEDs. Kinda gives the gauges a "tactical" look. I don't have pictures to post, but it looks pretty cool.

How much brighter were the LED's after install? I kinda like the red idea for gauges.

 

[Recovry4x4]

Anyone have a PN for the LED replacement bulbs? Never seen them before.

 

[dhedden]

LED's don't vary that much in intensity from their min and max voltage requirements. there should be a drastic difference in brightness. I know my dash lights work better or worse from one day to the next. i believe i'll give the LED bulbs a shot as well. Darn fine idea!!

 

[Warthog]

Anyone have a PN for the LED replacement bulbs? Never seen them before.

They is an advertiser that appears at the top of the page every once in awhile

http://www.steelsoldiers.com/cucv/46840-dash-light-bulbs-led-replacement.html

 

[SSMOORMAN@VERIZON.NET]

I also took my cluster out to replace bulb not working and also dim lights, come to find out i had a ground wire that was broken. All lights are bright now.

 

[cmroles]

I also took my cluster out to replace bulb not working and also dim lights, come to find out i had a ground wire that was broken. All lights are bright now.

Which ground wire was broken? The main ground above the e-brake pedal?

 

[stampy]

I painted mine (the plastic housing after removing everything) silver and cleaned all the contacts went back with dielectric grease and greased all the electrical connections and now they are bright.

 

[edpdx]

SSMOORMAN@VERIZON.NET, Yes, I too would like to know which ground you are referring to. I tore my cluster apart, polished all the copper "leads" and replaced with fresh bulbs. The headlight switch was also changed and still have a dim-watted cluster .

 

[Warthog]

The ground for the instrument cluster is indeed the Bus Bar Ground above the emergency brake.

I have attached the wiring diagram. I colored the wire BLUE so it would stand out. The wire in really black.

Remove the wire and the terminal block. Clean each and reinstall.

http://www.steelsoldiers.com/cucv/46054-cucv-instrument-cluster-decoded.html

http://www.steelsoldiers.com/electrical/43351-cucv-instrument-cluster-repair.html

Right click on the thumbnail and choose "Open Link in New Window"

 

[cmroles]

Well...I replaced the headlight switch today and did the same voltage test as before. Now, the voltage "begins" at ~10VDC and with the switch rotated all the way counter-clockwise it reads 12V. I haven't had a chance to test yet (cluster is still out), but this increased voltage should produce some results.

I also painted the inside of the metal trim panel silver as suggested by lavarok. I'm hoping that the extra voltage combined with the silver trim panel will brighten things up a bit!

 

[SSMOORMAN@VERIZON.NET]

Sorry just got home. Warthog explained exactly where my problem was. It effected my ignition switch it and wouldn't shut off all the time. It also effected my high and low beam, making them the opposit of what they should be. Sometimes I could turn the key to off and it wouldn't shut off until i pushed the light swich in. After finding broken wire and cleaning the terminal block, everything has worked fine.

 

[edpdx]

Warthog, thanks for the diagram and instruction. The blue wire in the diagram you provide... is there an actual blue wire coming off the cluster group that connects to the ground bus? The bus is the one against the cab on the driver side over the brake right? My bus had no wires attached to it. I have used it to ground my radio. Now it seems I have to figure out where the ground wire you indicate has gotten to. I knew **** well that the lights should be brighter

 

[edpdx]

Warthog, how about it. I just looked at the connector at the back of the cluster. I don't see a blue wire that would run to the ground you are advising of. Is it a single wire strand that is separate from the bundle?

 

[ralbelt]

ed in post #13 Warthog tells us that the wire is actually black, HE colored it BLUE to make it stand out so that it is easier for us to follow.

 

[edpdx]

ralbelt, check that, Black wire. I actually meant to say that I had not found the wire he had indicated as a ground that runs to the ground bus on the drivers side kick-under dash. Does anyone else have a wire that connects from that cluster connector to said ground block?

 

[Warthog]

ralbelt, check that, Black wire. I actually meant to say that I had not found the wire he had indicated as a ground that runs to the ground bus on the drivers side kick-under dash. Does anyone else have a wire that connects from that cluster connector to said ground block?

Somewhere under the dash you "should" find a single black wire floating around near the emergeny brake. It connects to the 6 lug bus bar. It controls alot of things. The tech manual even says that "If your truck will not turn off, you are to clean this connection".

This single black wire feeds back into the larger wiring harness and is hard to trace.

If the wire is missing someone has disconnected it an stuck it somewhere.

P.S. I don't read ever post every day. After I asnwer a question I usually move on to the next one. I usually don't go back and check old threads.