defender dinky Posted October 18, 2021 Share Posted October 18, 2021 Hi all, range rover classic efi 3.5 v8 flapper 1989, removed temp sensor the one that talks to ecu, done some tests have no resistance, tried sauce pan test boiling water slowly but nothing, part number says, lucas 33704A, but googled it but throws up 73355A, which I have but thread size is to small, also nut size on original one is 24mm, new type 19mm, where can I get lucas one, or is there an alternative? Need the brown one which is made in west Germany, dd Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 19, 2021 Share Posted October 19, 2021 In flapper EFI you have two sensors - the one on the left is a cold-start switch ONLY, the one on the right is a resistive temperature sensor for the ECU.... oh and there's one for the dashboard gauge too, that's only got 1 wire. Quote Link to comment Share on other sites More sharing options...
defender dinky Posted October 20, 2021 Author Share Posted October 20, 2021 Yh I know that, but I couldn't find a replacement for the faulty sensor, 33704A the brown one, so I found a bolt to fit the thread in the housing, then drilled hole through centre of bolt, then tapped it with the same thread as the new type 73355A, all fits nice and snug, just waiting now to test it, dd Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 20, 2021 Share Posted October 20, 2021 You don't seem to understand, the "old" brown one is a SWITCH not a SENSOR, replacing it with a sensor will not work. Quote Link to comment Share on other sites More sharing options...
defender dinky Posted October 21, 2021 Author Share Posted October 21, 2021 I think I've done it right, the one I done is brown one etc8496, in which I think has been superceded with 73355A, have I done this correctly, dd Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 21, 2021 Share Posted October 21, 2021 Sorry but nope, you're looking at the later Hotwire EFI system that doesn't have the thermo-time-switch, this is the flapper EFI setup: #12 is the temperature sensor (single-wire) for the dashboard gauge #14 is the thermo-time switch #15 is the ECU coolant temperature sensor #32 is the fan switch for the AC fans Although you may not notice any actual difference, replacing the thermo-time switch with a regular sensor will either stop the 9th injector working during cold-start and/or burn the new sensor out. Replacing the ECU sensor with a thermo-time switch or indeed with a different sensor (EG the gauge one) will just confuse the ECU into thinking it's colder or hotter than it is (so over or under-fuelling). If the old ECU coolant temperature sensor has been superseded it's OK to fit the new part. The sensor you originally removed appears to be the thermo-time switch which would probably test open-circuit at room temp anyway and is probably fine - put it in the freezer and test it again later. Edit: Found it in Ye Olde Almanac of Bosch EFI systems: And you can see the two switches and the 9th injector in this family photo: Quote Link to comment Share on other sites More sharing options...
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