Jeeper  Adventures Under the Hood  Jeeper

The Manifold Heater


The manifold heater's purpose in life is to heat the fuel mixture to aid vaporization when the engine is started at temperatures below 160 F. It replaces the common exhaust manifold heat riser valve. The heater itself is in the intake manifold under the carburetor. What is pictured here is the thermal switch that operates it. The switch is in the intake manifold's water jacket toward the rear. The green wire goes to a relay that is taped to the main wiring harness against the firewall. The red wire you see goes from the relay back to the heater. You should find 12 volts at this red wire, but only while the engine is warming up. The resistance between the red wire and ground is around 1 ohm, making the heater roughly a 200 watt unit. This heater is independent of the computer, and is not controlled by it.
Manifold Heater
If you dig around you will find that there are several of these relays taped in amongst the wiring harness snakepit.
Relay
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