# Need help with my truck



## sb47 (Jul 22, 2021)

I have a 1994 silverado 1/2 ton. My gauges dip when I put my blinker on. The fuel gauge oil and speedo all dip when the blinker is on. It has a new alt, and battery so I don't think that is it. It charges fine at 13v. I'm thinking the blinker module may be going bad. Chassy grounds are all good. Any other ideas whats going on with it?


----------



## pioneerguy600 (Jul 22, 2021)

Check all the electrical grounding points. Body to engine block is very important.


----------



## sb47 (Jul 22, 2021)

pioneerguy600 said:


> Check all the electrical grounding points. Body to engine block is very important.


Already checked that. I even added more grounding points awhile back. No change.


----------



## Fatherwheels (Jul 22, 2021)

An indicator module should be cheap enough, swap out the old with a new one,
there is very little else other than the indicator switch / stick shorting out, disconnect
the indicator module and flick the stick to see if it still dims the other gauges, if not then
its not the stick, its the module.


----------



## trains (Jul 24, 2021)

first thought is whats already been mentioned, especially a poor earth.
I would also offer checking any wiring loom connect point for corrosion where the male/ female pins and sockets join each other.
Start from the loom from the indicator switch where it joins the main loom, then trace from there, but usually its on that first join.


----------



## knockbill (Jul 24, 2021)

Poor grounds or loose/corroded connections are the first thing to check,,, I pulled teh dash on my 86 Dodge for the same problem, cleaned and tightened all plugs/jacks/bolts,, Some cars have dash voltage regulators, 5v I believe, to keep the gauges accurate if `the 12v supply sags (AC cycling, etc)


----------



## Clyde85 (Jul 24, 2021)

Could it be the gauge cluster it's self?


----------



## J D (Jul 24, 2021)

The gauges can be regulated at just about any voltage depending on what the manufacturer wants to do to keep their stuff proprietary. I would suspect the gauges & flasher are all powered by the same circuit & when the indicators are on it's drawing more current than the wiring can supply. Unlikely to be a faulty component as the amount of current to cause a voltage drop on good wiring would cause the fuse to blow.
Start by finding said fuse (it may even be the problem). Take a multimeter set to volts & measure the voltage on the fuse whilst the fault is present. If normal (12V) then wiring to fuse is good... Test wire leaving fuse... Wire entering dash... Etc... Etc...
Alternatively you can test the earth side of the circuit the same way, but you'd be looking for Voltage that shouldn't be there on what should be an earth wire.
The most likely scenario is that there is a poor earth to the guage circuit & it is finding earth through the blinker bulbs instead, when the blinkers are powered that earth disappears & your gauges play up. Do the blinker lights on the dash light up as brightly as they should?


----------



## J D (Jul 24, 2021)

Clyde85 said:


> Could it be the gauge cluster it's self?


Yep, or the connection to it


----------



## J D (Jul 24, 2021)

sb47 said:


> It charges fine at 13v.


13V is low for charging... That won't be the cause of your problem, but a good alternator should be charging at 14V give or take about half a volt. Might just be your meter though


----------



## cookies (Jul 24, 2021)

Check the Battery cables, pull back the rubber covers, remove their bolts and check their resistance from end to end disconnected. Those old GMs with side mount battery terminals are NOTORIOUS for battery acid seepage into the terminals and wiring.


----------



## sb47 (Jul 24, 2021)

J D said:


> The gauges can be regulated at just about any voltage depending on what the manufacturer wants to do to keep their stuff proprietary. I would suspect the gauges & flasher are all powered by the same circuit & when the indicators are on it's drawing more current than the wiring can supply. Unlikely to be a faulty component as the amount of current to cause a voltage drop on good wiring would cause the fuse to blow.
> Start by finding said fuse (it may even be the problem). Take a multimeter set to volts & measure the voltage on the fuse whilst the fault is present. If normal (12V) then wiring to fuse is good... Test wire leaving fuse... Wire entering dash... Etc... Etc...
> Alternatively you can test the earth side of the circuit the same way, but you'd be looking for Voltage that shouldn't be there on what should be an earth wire.
> The most likely scenario is that there is a poor earth to the guage circuit & it is finding earth through the blinker bulbs instead, when the blinkers are powered that earth disappears & your gauges play up. Do the blinker lights on the dash light up as brightly as they should?


Yes the indicator lights flash normally as they always have however, The clicking noise that a typical blinker makes is weak and I can barely hear it.I am old and hard of hearing but that may be indicating the flasher module is weak or going bad. A new flasher module is a cheap thing to try and I will do that on my next trip to the auto parts store. 
It started with just the fuel gauge doing the dip dance but now the oil and speedo are starting to do it as well. That tells me the problem may be getting worse.


----------



## CentaurG2 (Jul 24, 2021)

What? A GM instrument cluster not working right? Say it aint so. On my truck, all gauges are intermittent. It depends on the trucks mood what gauges it wants to have working on any given day or time. I would replace the turn signal relay. If that don’t fix it, it is most likely in the cluster itself. If you pull the panel out, there are companies that repair newer trucks for $75-150. I don’t know of a company that works on older stuff but they might be out there. I probably would just put up with it.



GM Gauge Cluster Repair, GM Instrument Cluster, Speedometer Repair (gmgaugerepair.com)


----------



## cookies (Jul 24, 2021)

The older clusters rarely ever failed but 99 and newer are junk, thats why I suggested checking the cables, terminals and grounds. I would also suggest getting that new alternator tested for a failed diode. Its also not uncommon to have a failed fuel level sending unit but multiple wonky gages points to what I first suggested.


----------



## holeycow (Jul 24, 2021)

I worked with a cat foreman in the bush who had his instrument cluster in his lap about 4 times on one job, This was about a 1 or two year old pickup in about 2006? Cluster failures were common. The boys had them figured after some trial and error. PITA.

So I concur with cookies. 

I like cookies!


----------



## J D (Jul 24, 2021)

If the alternator or battery/terminals was the issue you'd have issues whenever any high drain load (lights/heater/wipers/ect) was in use


----------



## cookies (Jul 24, 2021)

J D said:


> If the alternator or battery/terminals was the issue you'd have issues whenever any high drain load (lights/heater/wipers/ect) was in use


not necessarily, I fixed plenty of crusty battery terminal bolts, eyelits and replaced cables on chevys that would crank and run but had wonky gages, flickering lights, fluxuating blower motor output etc that solved the gremlins...those side post batteries caused electrical problems because batteries vent around the terminals and when mounted on the side its much worse.


----------



## siouxindian (Jul 24, 2021)

sb47 said:


> Already checked that. I even added more grounding points awhile back. No change.


yes . well you got a bad ground... you got a bad ground. old people know but sometimes we wrong also .you got a bad ground. check the back of the gauge panel . seen it before .


----------



## J D (Jul 25, 2021)

cookies said:


> not necessarily, I fixed plenty of crusty battery terminal bolts, eyelits and replaced cables on chevys that would crank and run but had wonky gages, flickering lights, fluxuating blower motor output etc that solved the gremlins...those side post batteries caused electrical problems because batteries vent around the terminals and when mounted on the side its much worse.


Maybe I should have said "unlikely".
I do agree with you when it comes to newer vehicles where everything is microchip controlled talking can-bus, the voltage fluctuations caused by poor connections can create havoc. I'm not particularly familiar with the Silverado but would expect it to be more of a "traditional" type of dash.


----------



## sb47 (Jul 25, 2021)

cookies said:


> The older clusters rarely ever failed but 99 and newer are junk, thats why I suggested checking the cables, terminals and grounds. I would also suggest getting that new alternator tested for a failed diode. Its also not uncommon to have a failed fuel level sending unit but multiple wonky gages points to what I first suggested.


My 12v charger has a battery check function and a alt check function, both check out ok. I'm not going to dig to deep into it until the summer heat wave settles down a bit. 100+ right now. To freaking hot to dig into something that can wait a bit.


----------



## cookies (Jul 25, 2021)

I feel ya on the heat, yesterday was a 108 heat index. This time of year I have to do things a few hours after dark when it cools off 20+ degrees. see if the problem persists if you use the hazards switch instead of the turn signal switch.


----------



## blades (Jul 26, 2021)

gauge cluster circuit board- delay timing solid state relay- when they start to go south all kinds of weird things happen. Not limited to gm industry wide. and yep like eveyone else has mentioned grounds- but one has to remember that the computer systems operate on their own circuits not chassis ground. All components have constant supply voltage on one side, the other side is switched ( you can call it the negative leg if you want) by the computer or various relay/ switch combinations which still feed back to various control modules. What this means is that everything operates above chassis ground. The various body components, frame, and Eng. ground are still important as some signals use these conections in a mutiplexing fashion. ( which I absolutely detest)


----------



## Okie (Jul 26, 2021)

*Have you checked the blinker fluid????*
O'Reilly parts counter will sell you some. You may have to tell them the color of your vec and the vin #. They will match the color of the fluid to the color of your vec.
If blinker fluid does not correct
TRY TO FIND THE DASH cluster VOLTAGE REGULATOR. It's usually replaceable and mounted on the dash Printed circuit board for the gauges.


----------



## Den (Jul 26, 2021)

Check for rodent damage. Chewn wires, connectors, etc.
Check the contact points inside connectors for corrosion. Put a dab of dielectric grease on each metal contact point while it's apart.
Alternate advice: Kick dashboard repeatedly/violently, and observe trucks reaction. This method works on computers also.

.


----------



## GeorgiaVol (Jul 26, 2021)

Bad grounds do funny things.
My cig lighter loses power when I open the door for some reason.
Not sure what yours is like, but the gauge light dimmer mechanism might be faulty. Mine acts up sometimes.
Of course if the bad ground is at the turn signal light itself, it might explain why there is a power drain when the bulb lights up.


----------

