Automatic Choke Heater Control Relay (PartTerminologyID 3140): Where Differentiation From PartTerminologyID 3016 Is the Mandatory First Listing Distinction

Written by Arthur Simitian | PartsAdvisory

PartTerminologyID 3140, Automatic Choke Heater Control Relay, is the relay that controls the power supply to the automatic choke's electric heating element through a dedicated heater control circuit that may include a thermostatic switch, a timer circuit, or an ECM output to manage the rate of choke opening during the cold-start warm-up phase. That definition covers the choke heater control relay function and closely parallels PartTerminologyID 3016, Automatic Choke Relay, from which it must be differentiated: PartTerminologyID 3016 covers the relay that directly switches the heater element power supply, while PartTerminologyID 3140 covers a relay in the control circuit that manages how the heater element is activated rather than directly switching its power supply current.

For sellers, PartTerminologyID 3140 is a narrow legacy application relay that must be differentiated from PartTerminologyID 3016 in every listing. The control relay handles lower current than the heater supply relay because it switches a thermostatic switch signal or timer output rather than the full heater element current. Installing a heater supply relay in place of the control relay will not damage the circuit but will eliminate the thermostatic or timed control of heater activation, causing the heater to activate from ignition-on continuously rather than on demand from the temperature or timer control circuit. The specific control circuit type must be identified to confirm the relay's role.

Listing Requirements

• PartTerminologyID: 3140

• control circuit type: thermostatic switch, timer, or ECM output (mandatory)

• coil and contact current for control circuit load (mandatory)

• differentiation from PartTerminologyID 3016: control relay versus heater supply relay (mandatory)

• application window: carbureted engines approximately 1965 through late 1980s (mandatory)

• OEM part number cross-reference (mandatory)

FAQ (Buyer Language)

What is the difference between the choke relay and the choke heater control relay?

The choke relay (PartTerminologyID 3016) directly switches the heater element supply current. The choke heater control relay (PartTerminologyID 3140) manages the control circuit that determines when the heater relay is activated, using a thermostat, timer, or ECM output. The control relay handles lower current than the supply relay.

What the Automatic Choke Heater Control Relay Does

The automatic choke heater control relay manages the control circuit that determines when the choke heater relay (PartTerminologyID 3016) is activated, using a thermostatic switch output, a timer circuit output, or an ECM coolant temperature output to command heater relay activation at the appropriate temperature or time condition. While PartTerminologyID 3016 directly switches the heater element's supply current, PartTerminologyID 3140 sits upstream in the control logic, switching the lower-current signal that commands the heater supply relay. The control relay handles milliampere-level signal currents from the thermostatic switch or ECM output rather than the full heater element current, and its contact rating reflects this lighter load.

Installing a heater supply relay in place of the control relay will not immediately damage the circuit because the contact ratings overlap, but it eliminates the thermostatic or timed control of heater activation. Without the control relay managing the activation logic, the heater element activates from ignition-on continuously regardless of coolant temperature or timer state, causing the choke to open immediately on every start rather than progressively over the warm-up interval. This produces lean cold-start stumble on cold mornings and wastes heater element life on warm restarts where the choke was already open.

Why This Part Generates Returns

Buyers return automatic choke heater control relays because the distinction from PartTerminologyID 3016 is not stated and a heater supply relay is delivered that bypasses the control function, the control circuit type is a timer on the buyer's vehicle and a thermostatic-switch-input relay is delivered with no timer interface, and the relay is delivered for a modern fuel-injected vehicle that has no automatic choke system.

Final Take for PartTerminologyID 3140

Automatic Choke Heater Control Relay (PartTerminologyID 3140) is the choke control circuit relay where differentiation from PartTerminologyID 3016 is the mandatory first listing distinction. The control relay manages the activation logic for the heater supply relay at lower current than the heater element load, and the two relays are not interchangeable despite both appearing in the choke heater circuit. Control circuit type identifying whether the relay responds to a thermostatic switch, a timer, or an ECM output is the second mandatory attribute. The carbureted application window from approximately the mid-1960s through the late 1980s is the third, ensuring the listing does not attract orders from modern fuel-injected vehicle buyers.

Listing Requirements

• PartTerminologyID: 3140

• control circuit type: thermostatic switch, timer, or ECM output (mandatory)

• coil and contact current rating for control circuit load (mandatory)

• differentiation from PartTerminologyID 3016: control relay versus heater supply relay (mandatory)

• application window: carbureted engines approximately mid-1960s through late 1980s (mandatory)

• OEM part number cross-reference (mandatory)

How do I identify whether my vehicle uses a control relay or a direct supply relay?

Trace the heater element wiring. If the element supply wire connects directly to the relay contact output, the relay is a supply relay covered by PartTerminologyID 3016. If the relay contact output connects to a second relay's coil or to a control module input, the relay is a control relay covered by PartTerminologyID 3140. The control relay typically carries much lighter wire gauge than the supply relay because it handles signal current rather than heater element current.

What is the symptom of a failed choke heater control relay?

Identical to a failed choke heater supply relay from the driver's perspective: the choke does not open progressively during warm-up because the heater element receives no power. On vehicles where the control relay uses a timer circuit, the additional symptom is that the heater activates at ignition-on on every start regardless of engine temperature if the timer relay is bypassed, because the timer's controlled duty cycle is lost.