gauge silliness
#665333
04/09/10 04:18 PM
04/09/10 04:18 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Okay, interesting problem in the 71 Demon. I have five Auto Meter gauges in my panel - voltage, oil press, fuel level, speedo, water temp. No problems with water temp, speedo, fuel level. But some interesting silliness with the oil pressure and voltage. You see, everything works out beautifully when the car starts and runs. All gauges show correct. But when I pull the light switch to either parking lamps or headlights, my oil pressure and voltage cease to work. Oil pressure buries itself past 100 and my voltage zeros out. No instrument lamps go on in these gauges either. Additionally, the dimmer switch on the light switch can be used to change the values of these gauges. At this point you're probably saying, "haha, this problem's easy! You have it on the instrument lamp circuit!" But that's where I can't figure this out. You see, my instrument lamps and my +12V leads to the gauges are on completely different circuits. Further, and here's the kicker, all the instrument lamps are in parallel with each other, as well as the +12V leads on a separate wire(see photo 1). So you'd assume that if two were having problems, the other three would be, too, because they get their power from the same place. So I decided to trace it - maybe I wired it wrong somewhere? I traced it back, and all of my +12V are going to the Dark Blue with tracer wire (DB* on the chart in photo 2). So not sure what's going on. Maybe a bad ground? Maybe something else. Any ideas as to how to test this?
|
|
|
Re: gauge silliness
[Re: sharpie]
#665334
04/09/10 04:19 PM
04/09/10 04:19 PM
|
Joined: Dec 2007
Posts: 7,759 So Cal
HealthServices
Why would you even post that?
|
Why would you even post that?
Joined: Dec 2007
Posts: 7,759
So Cal
|
Sounds like a ground issue.
Allen
Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first.
Life was a little easier when I was just a wrench.
|
|
|
Re: gauge silliness
[Re: HealthServices]
#665335
04/09/10 04:23 PM
04/09/10 04:23 PM
|
Joined: Dec 2007
Posts: 7,759 So Cal
HealthServices
Why would you even post that?
|
Why would you even post that?
Joined: Dec 2007
Posts: 7,759
So Cal
|
How are the headlights grounded?
Headlight switch?
The engine block has a good ground to the firewall?
How about the instruments?
Allen
Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first.
Life was a little easier when I was just a wrench.
|
|
|
Re: gauge silliness
[Re: HealthServices]
#665336
04/09/10 04:27 PM
04/09/10 04:27 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Quote:
How are the headlights grounded?
Dunno
Quote:
Headlight switch?
Dunno
Quote:
The engine block has a ground to the firewall?
The block has a ground to the battery (-)
Quote:
How about the instruments?
The instruments ground through an extra opening in the bulkhead connector and attach to a wiper motor nut/stud. My bulkhead connector may be bad, as could be the grounding point on the wiper motor, I suppose.
But why wouldn't they all have issues then?
|
|
|
Re: gauge silliness
[Re: HealthServices]
#665341
04/09/10 04:45 PM
04/09/10 04:45 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Quote:
I mean how does your system get ground if there is nothing going back directly to the battery? You have power going to everything but you don't have ground going to everything.
Good question. I am not sure. I guess it grounds to chassis then chassis to engine then engine to battery?
|
|
|
Re: gauge silliness
[Re: sharpie]
#665342
04/09/10 04:48 PM
04/09/10 04:48 PM
|
Joined: Dec 2007
Posts: 7,759 So Cal
HealthServices
Why would you even post that?
|
Why would you even post that?
Joined: Dec 2007
Posts: 7,759
So Cal
|
Quote:
Quote:
I mean how does your system get ground if there is nothing going back directly to the battery? You have power going to everything but you don't have ground going to everything.
Good question. I am not sure. I guess it grounds to chassis
Yes
Quote:
then chassis to engine
How?
Quote:
then engine to battery?
Yes, yes, and yes.
You can help it by installing a ground from the chassis to the battery [-]
For the gauges to work properly you need a good ground from the chassis to the engine.
This would be a good start.
|
|
|
Re: gauge silliness
[Re: HealthServices]
#665347
04/09/10 05:08 PM
04/09/10 05:08 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Quote:
Quote:
there's actually two separate grounds for the gauge panel. One is for all of the lights including the signals and hi-beam lights, the other is for all of the gauges. Each runs through the bulkhead and out to the chassis ground inside the engine bay on the wiper motor.
So there is a ground from the battery to the chassis? Or how is the ground getting back to the battery [-]?
Through the engine itself, I would think. Let me doublecheck my photos though.
|
|
|
Re: gauge silliness
[Re: HealthServices]
#665349
04/09/10 05:12 PM
04/09/10 05:12 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Quote:
Quote:
Through the engine itself, I would think. Let me doublecheck my photos though.
Hopefully not thru the motor mounts.
why is that bad? the bolt touches each side, no?
|
|
|
Re: gauge silliness
[Re: stumpy]
#665352
04/09/10 05:33 PM
04/09/10 05:33 PM
|
Joined: Sep 2007
Posts: 5,037 hi
sharpie
OP
Moparts Linguist
|
OP
Moparts Linguist
Joined: Sep 2007
Posts: 5,037
hi
|
Quote:
Motor mounts are rubber and don't ground to the frame. You diffenately need a ground from the block to the body and to the frame.
What I don't understand here is the car runs fine, charges fine, and even has voltage to spare. It's just the gauges.
|
|
|
|
|