What is this??

[Nategill04]

Sorry if this isn't the right section. Never posted on forum's before. Need help identifying what this is in my 82 c20. The box with the five wire connector going to it. It was hanging by the manifol when I bought the truck, I screwed it to the fire

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wall.

 

[Ricko1966]

Its a relay,is it on a factory socket or has this been added.

 

[newguy11]

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[Finkaire]

Blower relay?

 

[75gmck25]

If you have dual batteries, it could be the battery relay. On my K20 it connects the 2nd battery when the engine is running, so it will chsrge, and then disconnects it when you turn off the ignition, so it can power a camper.

 

[Craig 85]

Do you have one of these factory aux fans behind the grill? If so it could be the relay to that. There's a sensor on the passenger head that triggers the fan. I added it to mine, but it is the correct location using a Napa parts.

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[Rustisbest]

Flux capacitor. Keep it under 88 mph.

 

[mrdap]

That is called the speed switch.
454 only. It's essentially a relay that's activated by RPM as sensed from the distributor. At 1,900 RPM, the relay contacts close, activating the speed switch valve.
Reference Figure 8C-45-CK Series wiring page 2 of 29, from the 1982 service manual, page 8C-53.
To tell you what that speed switch valve actually does, I'll have to go out and look at my '82 K20 454. My guess is it's an electrically controlled vacuum switch related to emissions control.

 

[Radiohead]

So that's what is on the schematic that no one else has ID'ed.. yet.

Kewl!

 

[mrdap]

Okay, this is part of the throttle return control (TRC) system.
See pages 6E-2 and 6E-26-6E-28.
Only exists on HD emissions equipped vehicles.
Essentially it's an electro-vacuum system that operates above 1,900 RPMs (1,890 RPM to be exact).
Above 1,900 RPM, the system actuates and prevents the throttle blades from snapping closed too quickly when you take your foot off the throttle.
On my 1981 K30, the speed switch is attached to the firewall.
On my 1982 K20, the speed switch is attached to the left hand valve cover.
The electro-vacuum switch is located just to the left of the thermostat housing.
And then there's a vacuum actuator that's attached to the carburetor.
These parts are very difficult to find nowadays.
Most people just rip them off and forget about it.

 

[Craig 85]

Okay, this is part of the throttle return control (TRC) system.
See pages 6E-2 and 6E-26-6E-28.
Only exists on HD emissions equipped vehicles.
Essentially it's an electro-vacuum system that operates above 1,900 RPMs (1,890 RPM to be exact).
Above 1,900 RPM, the system actuates and prevents the throttle blades from snapping closed too quickly when you take your foot off the throttle.
On my 1981 K30, the speed switch is attached to the firewall.
On my 1982 K20, the speed switch is attached to the left hand valve cover.
The electro-vacuum switch is located just to the left of the thermostat housing.
And then there's a vacuum actuator that's attached to the carburetor.
These parts are very difficult to find nowadays.
Most people just rip them off and forget about it.

Good catch. I didn't look close enough at his picture to see it's the driver's side. My '85 K30 has it on the driver's valve cover too. Here's the some pics of the other related items.

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