Speedo only turns on when key is turned to Park

[rywilly]

Anyone know why this new GPS speedo I've installed only turns on when I turn the key past the on position to the park position?

Maybe my wiring diagram isn't correct? Does anyone have a better one?

Its installed on my 78 GS550.

 

[Big T]

Well, what wiring diagram do you have?
The one on the factory service manual?
Obviously, you're connected to the wrong wire

 

[rywilly]

Found one online - I don't have a service manual and it hasn't been easy finding a high resolution one on the web. I think this one might be from 80s? Nothing is marked well.

 

[chuck hahn]

http://zeus.mtsac.edu/~cliff/storage/gs/GS550_77-82_all.pdf

 

[Steve]

Some wiring diagrams are incorrect, especially around the ignition switch area.

What wire did you connect to? At the ignition switch, there are four wires: Red, Orange, Gray and Brown.
The Red wire is connected directly to the battery (through the MAIN fuse), it will always be "hot".
The Orange wire is right after the ignition switch, it sends power to the fuse box.
The Gray wire is powered from the lights circuit.
The Brown wire is fed from the Red or Gray wire, depending on key position (Park or Run, respectively).

You could tap into any of them except the Red one for switched power. However, ... if you use the Orange wire, you should install a separate in-line fuse for the speedo, so you don't rely on the 15 amp MAIN fuse. If you use the Gray or Brown wires, you will be downstream of the LIGHTS fuse. If you blow that fuse, your speedo will quit, but you will also know that your tail light is not working. :encouragement:

.

 

[Sandy]

You maybe connected to the brown wire inside the headlight shell which is only activated when the key is in the park position???

 

[Gorminrider]

^ excellent guess! a lot of bikes have an empty socket there for English parking lights. Usually grey wire powers gauge back-lights....

 

[rywilly]

Connected it to the brown wire, this is helpful! Thanks!

Some wiring diagrams are incorrect, especially around the ignition switch area.

What wire did you connect to? At the ignition switch, there are four wires: Red, Orange, Gray and Brown.
The Red wire is connected directly to the battery (through the MAIN fuse), it will always be "hot".
The Orange wire is right after the ignition switch, it sends power to the fuse box.
The Gray wire is powered from the lights circuit.
The Brown wire is fed from the Red or Gray wire, depending on key position (Park or Run, respectively).

You could tap into any of them except the Red one for switched power. However, ... if you use the Orange wire, you should install a separate in-line fuse for the speedo, so you don't rely on the 15 amp MAIN fuse. If you use the Gray or Brown wires, you will be downstream of the LIGHTS fuse. If you blow that fuse, your speedo will quit, but you will also know that your tail light is not working. :encouragement:

.

 

[Redman]

Connected it to the brown wire, this is helpful! Thanks!

(If like the Gs that I m familiar with, and I think it is) Brown wire is tail light (and tail light only, not any marker lights, not tag light, not instrument lights) and that should be powered in the ON position and in the PARK position.
To say a portion of that again, in different words: THe brown wire should be powered in the On position AND in the Park position.

(That is what Park position is, power the tail light and tail light only, powered by Main fuse Red Wire.)

So....in addition to your original concern.... : Do check to see if you have a tail light when in ON position. Well, only if you think that is important.



.

 

[Redman]

.
Maybe my wiring diagram isn't correct? Does anyone have a better one?
..

The function chart of early edition Clymer manauls schematics (again, for the Gs that I know)were hard to interpret or outright wrong on the function of the ignition swtich. Schematic wiring diagram okay, wire from here to there, but it was the little chart for what connects to what inside the switch what key position that was suspect (wires in reverse order I think I recall).

I can describe the wires and the switch functionality all verbally if you want,.....

Later note>> Now I see that Steve has described wires and the switch function.
I would say about the same thing.
Let us know if you have any further questions about that.

.

 

[Steve]

... the brown wire inside the headlight shell which is only activated when the key is in the park position???

Not quite. :-k

True, the brown wire only powers the tail light, but it is active in PARK and RUN.

.

 

[Gorminrider]

must be the "-" then. Don't just "ground" it to the headlight bucket-attach it to a black+White wire..polarity of the speedo's bulb wires doesn't matter unless it's an led.

 

[Redman]

must be the "-" then. ....

He says it comes on when in Park, so the problem isnt the negitive.

 

[Redman]

ry,

THe problem isnt that you are connected to the brown.
THe brown should have power in ON and in Park.
THe problem is that there is some problem that dont have power on the brown in the ON position (and as such, you probably dont have a tail light in the ON position).

Lets talk more about the function of the key swtich:

In ON (Run):
THe swtich should connect the Red (from Main fuse) to the Orange which then goes to power the Head and the Signal and the Ignition fuse.
And it also should connect the grey (from Signal fuse circuit that powers all the other instrument lights ) to the Brown wire to the tail light only.

In the PARK position:
All THe switch does is connect the RED (from main fuse) to the brown to light the tail light and tail light only.
Does nothing with the Orange wire for Head, Signal and Instrument fuse.

So: You need to see why dont have power on the brown in the ON position.

Let me print out your schematics.

 

[Redman]

A 78, right....?
Looks like the gray wire gets powered by contacts in the headlight switch.

 

[Gorminrider]

yes,backlight bulb just needs connection to grey (gauges+) and black/white stripe (ground-) . but so often aftermarket gauges come with a passel of wires in a different colour code...maybe Honda is their usual choice? green =ground-, black , red,grey or ? =+