jerrytr5 Posted October 6, 2024 Report Share Posted October 6, 2024 Had a good day at Prescott with the 7 sprint, just before the rain. Jumped in to drive home & no wipers. Checked fuses & blown. Replaced & immediately blew. Googled the issue & someone had similar issue & suggested starting the engine & then replacing the fuse. Christ, it worked & got me home. I can't figure how running the engine prevents the fuse blowing. Any suggestions? Jerry Quote Link to post Share on other sites
RobH Posted October 6, 2024 Report Share Posted October 6, 2024 The fuse powers a number of other things as well as the wipers (coolant level and fuel level indicators etc) so perhaps it's one of those whose state changes when the engine is running and so removes a short circuit ? Quote Link to post Share on other sites
jerrytr5 Posted October 7, 2024 Author Report Share Posted October 7, 2024 Won't be able to track this down for a week or two, so will get back when I find something. Indicators also on this fuse so a few circuits to check. Thanks for the clue Rob. Jerry Quote Link to post Share on other sites
RobH Posted October 7, 2024 Report Share Posted October 7, 2024 A further clue would be exactly when the fuse blows. Is it when the ignition is first switched on, or when the engine is cranked ? If it happens immediately when you turn on the ignition, you can find the short more quickly by disconnecting the coil (to prevent it burning out) and replacing the fuse with a small 12v bulb (not LED), which should light with the ignition on because of the fault current. Leave it switched on and disconnect each circuit in turn until the lamp goes out - showing that is the faulty one. Quote Link to post Share on other sites
jerrytr5 Posted October 7, 2024 Author Report Share Posted October 7, 2024 Fuse blew as soon as ignition turned on (quite a flash from the 35amp fuse blowing). Nice tip using a bulb, but the fuse is blowing to prevent a meltdown, so won't the test bulb create some of Mr Lucas's fabled smoke by completing the circuit? Jerry Quote Link to post Share on other sites
RobH Posted October 7, 2024 Report Share Posted October 7, 2024 No it will just light up. A small bulb ( i.e. interior festoon or similar) doesn't allow much current so there will be no damage. Quote Link to post Share on other sites
jerrytr5 Posted October 7, 2024 Author Report Share Posted October 7, 2024 So I had to move the car & expected the fuse to blow as soon as I turned the ignition on. Of course, everything now works so I'll be tracing an intermittent fault. Doh! Quote Link to post Share on other sites
stuart Posted October 8, 2024 Report Share Posted October 8, 2024 20 hours ago, jerrytr5 said: So I had to move the car & expected the fuse to blow as soon as I turned the ignition on. Of course, everything now works so I'll be tracing an intermittent fault. Doh! Welcome to the world of TR7 electrics, they were always problematical. Stuart. Quote Link to post Share on other sites
jerrytr5 Posted December 7, 2024 Author Report Share Posted December 7, 2024 I know it's been a while, but other priorities got in the way. It still didn't blow the fuse again so I hunted down the coolant level control module which it turns out is a cylindrical gadget under the dash. Then I got lucky as it seems there have been previous issues here given the state of the multiplug (photo). As the car doesn't have a low coolant indicator fitted I chose to terminate all the wires neatly (two black wires together) and see how it goes. One of the green wires powers the choke warning light and as the switch isn't fitted either was also eliminated. I was going to look at the low fuel warning, but I'm reasonably confident that the dodgy multi-connector was likely the issue. Jerry Quote Link to post Share on other sites
stuart Posted December 9, 2024 Report Share Posted December 9, 2024 On 12/7/2024 at 9:39 PM, jerrytr5 said: I know it's been a while, but other priorities got in the way. It still didn't blow the fuse again so I hunted down the coolant level control module which it turns out is a cylindrical gadget under the dash. Then I got lucky as it seems there have been previous issues here given the state of the multiplug (photo). As the car doesn't have a low coolant indicator fitted I chose to terminate all the wires neatly (two black wires together) and see how it goes. One of the green wires powers the choke warning light and as the switch isn't fitted either was also eliminated. I was going to look at the low fuel warning, but I'm reasonably confident that the dodgy multi-connector was likely the issue. Jerry TR7wiring was never its strong point Stuart Quote Link to post Share on other sites
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