Electric Heater for Jeep Water Jacketed Intake Manifold
Good Question.....
The Jeep Alumium intake has a water jacket to maintain a heated constant temp to deliver a better air / fuel mixture. Cold weather, hot weather, damp weather... one way to make it better was a water jacket and heat it with the engine coolant. It also uses a larger electric heater when first started up till the engine coolant reaches operation temp.
This is a larger heater, I did the amp draw calc and its pretty large so a relay is needed. Do not run this heater with a direct ignition control...
So this how it works..... The red wire you show on the bottom is the 12V, the heater gets the ground from the mount to the intake, mounted to engine, mounted to block ground to battery. So it has a ground and 12V +........ we will use the 12+ for control.
ON the intake there is also a coolant switch that is NC, normaly closed, and when the coolant reaches 160F the coolant switch will open. When this opens or reaches 160 the electric heater can be shut off. Use a multi meter to ck with switch... Cold will have continuity with ground or the manifold...... at 160F+ the end will not longer show ground contact with manifold...
Control of Electric Heater...
We use a normaly OPEN relay with 20-30 amp rating....... For now we will keep it a bit simple...... The Key on will supply the 12V+ to the relay coil and close the relay. The ground to the relay coil will come from the coolant 160F switch on the manifold. The INPUT/OUTPUT POWER the relay controls will be from the battery or fuse block....... this power should be fused with a 15amp or 20 amp fuse. Sorry just do not remember the power consumption and do not have time to look up right now... Could look in the FSM, Field Manual, and see what fuse was use in the OEM hook up because we are not changing the power needs.... Either one should work fine.... so start with the 15 amp if you do not further looking...
So we turn the key on and the relay get energized with the coil closing the relay... Power 12+ from fuse block or battery will power the electric manifold heater. When engine get to temp, 160F+, the coolant switch on the manifold jacket will now open and cut off the 12V- ground to the relay coil control and then the NO relay will go to the resting state of NO and the electric heater will no longer have power....
How do we use the Oil Pressure Switch?????
Another good question.....
General guide line is not to load up the ignition key with extra AMP load and make it fail... We need the key switch to make it home... 80s Jeeps use a oil pressure switch to turn on a few aux devices so they coudl be taken off the key switch.....AND the battery draw till the engine is actually runnning. The idea was once the engine is runningn and we need lots of power / AMPs to turn over the starter/engine esp when its very cold. So..... lets take that load off the battery/key start and use a oil pres swithch to turn on some items once the engine is RUNNING and has oil pressure... Also nice because if the engine is not longer running and has oil pressure can shut off aux heater, fuel pump, and other devices for safety should turn off...
So to use this.... The Oil Pres Switch would control a relay that would turn ON/OFF another 12+ source. This system would control the 12 V+ to the heater relay control.... So what we discussed above would stay the same....... but the igntition key to put 12V+ to the heater control relay would be replaced by the oil pessure switch control relay...
The OIL PRESSURE SWITCH... controls the ground or a 12V+ supply.. Could be either one... Usually it controls ground...
A cool trick... Jeephammer showed me
A grease gun wip is 1/8" NPT threads and will thread into the block.. Run the wip to a 1/8 and 1/4" NPT manifold block. Mount block on firewall or fender and put your oil press switch, oil sender for gauge, mech pressure gauge. Takes these parts off the vibrations/heat of engine, they last longer and is a nice way to hook the stuff up.
I started with the Key controlling the relay to activate the heater.. The 70s did not have a oil switch but good idea.. I added a manifold and oil switch several months back but have not hooked it up... But good method to control aux devices like manifold heater, electric fuel pump, engine cut off control...
hope that helps
