skidoo_j Posted February 25, 2014 Share Posted February 25, 2014 The Purpose of the extended Idle was in police vehicles when sitting still using extra accessories to prevent too much strain on the motor. For post 93 jeeps there are a plethora of how to pages on how to add this feature Why would you want extended Idle or a higher idle? well many reasons, winch recovery, lights, On board air, overheating (assume good clutch fan) After several hours of research all that I've found for doing the extended idle was for post 93 vehicles where a police version was available. After reading pages and pages of forums discussing the post 93 and people just begging for how to do it on pre 93 vehicles but I was unsuccessful in finding it. I acquired a 90fsm and searched it my self and found no direct options listed. But then Blue88Comanche suggested piggybacking the up idle from the ac circuit. Yeah it's not a true extended idle and the idle isn't increasing to 1k rpm like the extended idle but 300-400 rpm increase is plenty for my purposes. Again Back to the wire diagrams I went.... What I found:There are two inputs to the ecu for the A/C. One from the physical switch giving power to the a/c circuit then a second that comes off the a/c thermo. The ECU looks for voltage on these two contacts then increases the Idle expecting the draw from the ACpump. Connections c2 and d2.An attempt to further explain the a/c electrical: when a/c is selected power goes to the low pressure switch at the condenser, comes back into cab and is split; one of these splits goes to the ecu at d2. A second split goes to the a/c thermo then runs back to ecu at c2. a third leg supply power at the a/c relay for both the aux fan and the compressor, but this power is controlled through a relay by the output of ecu a12. when c2=d2(12volts) idle increases expecting the load and at the same time a12 powers the relay in engine compartment closed and the compressor is activated with the fan. I don't have A/C So I was not concerned with what I did. And alot of the A/C circuitry is not there just stuff in the factory loom... If you have a/c and want to retain the use of a/c a few relays maybe needed to break different circuits, and probably cutting and tapping into wire as they enter the ecu rather than tying into them down stream in the harness like i did. Wire diagrams referenced are from the 90 fsm 22,74, 75, 76I did this to an 89 4.0 although based on the wire diagrams for the 2.5 it should be the same too, but different pins on the ecu, connector behind the fan switch listed below is the same though. The HOw: It's pretty simple, Remove dash bezel, remove stereo, loosen the heat controller. Look for this six pin plug behind the fan controller. Mine had 5 wires on the female side and only 2 or 3 on the male side Decide your location for your high idle switch and your 12 volt source (I used a tap off cig lighter as i already have a modified circuit controlling that power). You'll run the switched power to the connector and connect it to pins a and b a light green wire and a light brown wire. I got two jeep connectors from a male donor plug and wired it in the the male side of the factory plug so it's clean: (this is a soldered connection heat shrunk with dual wall then I wrapped with electrical tape for stress, anal or overkill you choose)I fed these contacts off a "fan diode assembly" that was a donor from the jy with a/c. There are three connections on these the two outsides are source in and the middle is output. They do not allow back feed and are rated to 1.5 amp (since everything is on relays and just the ecu no worries) anyways on one leg I tied my manual aux fan switch and the other leg to my future elocker switch. When I use these I clean them, and change the gray and orange wire so that the two inputs are the same color, when this is in the factory position the grey wire comes from the thermostat in the radiator, the orange "in" is from the a/c circuit and the orange "out" controls the fan relay.nice and finished and works flawlessly: Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted February 25, 2014 Share Posted February 25, 2014 Video of this in action, please! :bowdown: :bowdown: :bowdown: Link to comment Share on other sites More sharing options...
Keyav8r Posted February 25, 2014 Share Posted February 25, 2014 Well written "how to do it"! I'm electrically challenged but could follow this easily. Good work, Skidoo! Link to comment Share on other sites More sharing options...
Spectormj Posted February 25, 2014 Share Posted February 25, 2014 Onlyinajeep is right we need to see this on video might help all of us here Link to comment Share on other sites More sharing options...
skidoo_j Posted February 25, 2014 Author Share Posted February 25, 2014 Alright here's a quick half @$$ video. Was shot with engine warm. Again this was done on an 89 4.0 that has been very unmolested and no previous wiring issues, so anyone who attempts to follow what I did its on you to do your own due diligence. This includes following the wiring schematics yourself and ensuring your wire loom has not been hacked up already. You can or could fry ... if your loom is messed up. http://www.flickr.com/photos/skidoo_j/12776209564/ anyone wants to edit the post to embed the video that's fine www.flickr.com/photos/skidoo_j/12776209564/ Link to comment Share on other sites More sharing options...
Blue88Comanche Posted February 27, 2014 Share Posted February 27, 2014 Nice write up! Link to comment Share on other sites More sharing options...
Blue XJ Posted March 19, 2014 Share Posted March 19, 2014 Nice writeup, I'll have to give this a try. It'll come in handy when using my on board air. Link to comment Share on other sites More sharing options...
danbyrambler Posted March 20, 2014 Share Posted March 20, 2014 IF the truck has AC could you just toggle/rocker switch the compressor clutch ground? RPMs up - Fan runs - Just a thought Link to comment Share on other sites More sharing options...
skidoo_j Posted March 20, 2014 Author Share Posted March 20, 2014 IF the truck has AC could you just toggle/rocker switch the compressor clutch ground? RPMs up - Fan runs - Just a thought If I had a/c.... I'd cut a12 out of the ecu. install a relay with pins 30 connected on ecu side and 87 to the truck side. would also wire c2 at the ecu probably with a diode contact a to truck b to ecu c to switch then cut wire d2 and attach a diode with contact a to the truck spliced to pin 85 of the relay. contact c to the diode do your switch and output ( B) to the ecu. final wire to pin 86 to ground. what this would do would allow the override to lock the ecu in constant high rpm with out runing the a/c pump constantly, but would still allow the a/c pump to cycle with the thermostat as designed. If really needed i can draw out a schmatic of this idea and others could comment or use it. Let me know if it's desired. Link to comment Share on other sites More sharing options...
Blue88Comanche Posted March 20, 2014 Share Posted March 20, 2014 IF the truck has AC could you just toggle/rocker switch the compressor clutch ground? RPMs up - Fan runs - Just a thought If I had a/c.... I'd cut a12 out of the ecu. install a relay with pins 30 connected on ecu side and 87 to the truck side. would also wire c2 at the ecu probably with a diode contact a to truck b to ecu c to switch then cut wire d2 and attach a diode with contact a to the truck spliced to pin 85 of the relay. contact c to the diode do your switch and output ( B) to the ecu. final wire to pin 86 to ground. what this would do would allow the override to lock the ecu in constant high rpm with out runing the a/c pump constantly, but would still allow the a/c pump to cycle with the thermostat as designed. If really needed i can draw out a schmatic of this idea and others could comment or use it. Let me know if it's desired. That sounds like an awesome idea for us with AC. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted March 20, 2014 Share Posted March 20, 2014 I've thought about up the idle by creating a vacuum leak that I can control from the cab somehow... maybe that's a bad idea but just a though... simple too. Link to comment Share on other sites More sharing options...
skidoo_j Posted March 21, 2014 Author Share Posted March 21, 2014 I've thought about up the idle by creating a vacuum leak that I can control from the cab somehow... maybe that's a bad idea but just a though... simple too. I like that idea. connect it to an electric valve and into the post filter air. Link to comment Share on other sites More sharing options...
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