I pulled this out and measured voltage at the sensor and like you guessed none showed. Wouldnt this be the best way to disable the fuel heater and leave it pluged in. Does this control something else on the vehicle.

This is what I do during the summer, rather than have dust get in the plug.

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05CRD: GDE Hot ECU & TCM tunes, Provent, Cat filter, Facet lift pump, TransGo kit, Florida TC, Samcos, stainless brake lines, HDS thermostat, Renegade light bar,
RL super sliders, Bilstein adjustables, Al's Gen 4.5 Arms, 235/85-16 Duratracs, DTT rear, Elocker front, EVIC+TPMS, Turbo timer, McNally pillar gauges, Weeks Stage II kit.

I made another relay without an armature. The cover of the relay pops off - the armature rips out. That keeps something in the relay socket and keeps it clean also.

Made it through last winter without needing it. If I have problems, pop in the 'real' relay and it's on again.

I also did the same for the viscous heater clutch.

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2005 CRD Limited Flame Red w/ Renegade rock rails & light bar, AirLift 1000. 225/75R16 MT/R's on cheap black steel wheels, dual MOPAR subwoofers, Ipod kit & seat covers, Samco hoses - totaled and gone. 2008 WK Laredo 3.0L diesel - AirLift 1000, wife won't let me mess with it much. 2013 JK Sahara on order.

Why not just pull the fuse for the fuel heater?

Gary

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'05 Lt. Khaki Sport; 245/75R16 Goodyear Wrangler Duratrac Tires
Fumoto/Shell Rotella 5W40/Napa Gold oil & fuel filters, Dodge Cummins Lift Pump
SEGR, GDE Hot Tune & Transmission Tune, Aux. Transmission Cooler, Euro TC
front receiver hitch pending,
Factory Skids
Frankenlifted

... that switches the relay ground off when it is warm.
All I need to do now is adjust it so it comes on in colder weather instead of 40f.
I will try to set it so it comes on at 10f and lower.

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2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle

Hmm, interesting idea. Got a parts list? I might play on Grainger later to see if they have any temp-controlled switches that might work too.

Got mine from ACE Hardware, they use them in crawl spaces to keep pipes from freezing up in the North. In the not so deep South, house trailer water hook up are popular. Thermostat is in the end of the Heater tape.

My pics: http://picasaweb.google.com/warp2diesel ... oTalMrhbw#

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2006 Pearl Green CRD
Magnaflow 2 1/2" Cat Back
KJ Extra Leg Room Brackets, Carter Lift Pump, V6 Airbox, ORM
Fuel cooler, Oil Separator, Progard 7
Gauges EGT Boost Trans Temp Oil Pres, Michelin LXT AT2 245 70 R16
7,000# Draw Tight hitch, PML EX Deep Trans Pan
Centrifuge, SunCoast, Transgo, RAM TCM, InMotion Stage 2
Wife's 99 TDI VW Beetle