Choke Light?

[plumtruckerd]

I took my '86 GMC 3500 out for a drive and noticed an orange light come on in the instrument panel. It stayed on for just a second and flickered and faded out. Did it a few times, mostly when going up hill. I never knew there was such a thing as a choke light, not sure what triggers it? It does have a mechanical electric choke, that appears to be working properly. What do I look for?

 

[EvilGenius]

The "Choke" light circuit should only ever be on at the key on position without the engine running. It indicates that the electric choke is on and is not going to turn off in it's current state. The way it is wired is thus:
-When key is on 12v is applied to one side of an engine oil pressure switch (not sender)
-With no oil pressure, voltage is directed through the choke light circuit to turn on indicator
-When oil pressure is present, voltage is instead directed to electric choke circuit (which then opens over time if choke is set up properly) (Light is not on in this path)

So if your choke light is coming on intermittently you could have a large problem or a small one. The more likely scenario is that the oil pressure switch is on the way out. This is usually located either under the distributor or in a port directly above the oil filter. The unlikely but scary problem is your oil pump is going out or something else is causing you to lose oil pressure. If you have an oil psi gauge you can probably verify this when the light is flickering.



Take all this with a grain of salt as this is one of the commonly modified circuits people love to cut up. If your truck has ever had an aftermarket carb put on it people almost never hook this circuit up the way the factory put it. This is also model year dependent I believe. Look up the wiring diagrams for your year. Should be straightforward to verify.

 

[plumtruckerd]

I do have an oil pressure gauge, and it is running at normal pressure, so that shouldn't be the issue. I did recently replace the valve cover gaskets, maybe something is a little loose from doing that. I'll have to check the switch. Thanks for the info