monorfolk Posted August 15, 2023 Share Posted August 15, 2023 Hi, I have a P reg Defender 90 300Tdi. I had some problems with the coolant temp gauge so replaced the rad, temp sender and meter to modern versions. All is now good (not overheating) but when I switch on the headlamps the temp gauge rises from 90 degree to 100, indicating a grounding issue. An extra ground cable has already been added from the bulkhead grounding point (that goes to the instrument cluster) to a bolt just under the air filter, as the engine ground is OK, zero resistance to the -ve battery terminal and starts fine, but the issue still remains. There is about a 3 Ohm resistance from there to the engine which I think is the issue. Any suggestions on where on the engine can I route the extra bulkhead grounding cable to ensure a good earth return? I would assume where the starter motor is grounded but somewhere more convenient would be good. Quote Link to comment Share on other sites More sharing options...
monkie Posted August 15, 2023 Share Posted August 15, 2023 The short answer for a quick and convenient fix would be to send an earth via nice thick cable to a bolt holding an engine lifting eye to the engine, ensuring the bolt etc are all clean. A better place with slightly more work could be one of the bolts holding the bell housing to the engine. The best thing to do with earths (the best thing I have ever done to my 110) is to have a number of dedicated earth points located in each corner of the vehicle (for lights) and then on the bulkhead (for the other stuff), which all in turn are earthed straight back to the battery negative terminal by a nice thick wire. That way you are bypassing the reliance on the 25+ year old factory earths and ridding your land Rover of potential earthing faults for a long time. What ever you do, follow the original wiring colour codes to help you in the future with any wiring problems 1 Quote Link to comment Share on other sites More sharing options...
western Posted August 15, 2023 Share Posted August 15, 2023 Clean all the earth wires at bulkhead bolt adjacent to clutch pedal assembly Quote Link to comment Share on other sites More sharing options...
Ibex94 Posted August 15, 2023 Share Posted August 15, 2023 I'm surprised a lighting earth is affecting the temp sender, but earths and cars are strange things. You will get a good continuity reading with a light piece of cable which when loaded will generate a potential drop. Also a poor or corroded connections will also affect the quality of the earth. The battery earth usually bonded to the chassis and then to the back of the transfer box. Worth a check and a bit of clean up. Then look at the bulkhead earthing stud and potentially clean up the contacts if necessary. From memory the light earth earths run back to there. I added an engine earth from the near side chassis leg to the block beneath the alternator, just to make sure the engine was well earthed. Quote Link to comment Share on other sites More sharing options...
monorfolk Posted August 15, 2023 Author Share Posted August 15, 2023 Hi, Thanks for all the suggestions. On further measuring the extra bulkhead instrument cluster grounding point to the grounding point on the engine seems good. Possibly its an engine to battery ground fault but I would have assumed in that case the starter motor would have issues due to the large current draw therefore voltage drop. Looking back at previous posts monkies suggestion to create a few new grounding wires seems the way to go. Thanks again.. Quote Link to comment Share on other sites More sharing options...
monorfolk Posted August 15, 2023 Author Share Posted August 15, 2023 I'm tempted to run a new earth cable from the bulkhead grounding point (therefore the engine with the extra wire) direct to the battery but am worried if the engine ground IS dodgy, the starter motor current will prefer to use this route and burn it out. I shall first check out the engine ground cable if I can find it.. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted August 15, 2023 Share Posted August 15, 2023 I ran an earth from the battery to the chassis and another from the same point on the chassis to the engine block right by the starter…. then a smaller dedicated earth from the battery to the bulkhead earthing point. Perhaps something like that would work. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 16, 2023 Share Posted August 16, 2023 I'm confused by your description of the various grounds... "Bulkhead to air filter" ground is OK? Engine to battery -ve is OK? Which one has the 3ohm resistance "from there to the engine"? I do Monkie's system - a dedicated earth wire to each corner as well as a chunky one to the engine (my engine earth is to one of the starter motor mounting bolts) and in my case a chunky one up into the dash to a small buss-bar where I can earth everything back there, otherwise it's all just relying on bodywork/chassis connections to get back to the battery. 1 Quote Link to comment Share on other sites More sharing options...
Sigi_H Posted August 16, 2023 Share Posted August 16, 2023 The temp sender is connected to ground via its thread. This can be bad either if screwed in with Teflon tape or locktite. Quote Link to comment Share on other sites More sharing options...
simonr Posted August 16, 2023 Share Posted August 16, 2023 My go-to mod on all my Land Rovers is a 35mm cable from the battery -ve to one of the starter motor mounting bolts. The braided connections from the battery & engine to the chassis are not great at the best of times & the chassis is a poor conductor. I've left these in place, more to ground the chassis than provide a ground to the engine. The starter draws the most current - and benefits the most from this. Quote Link to comment Share on other sites More sharing options...
Junglie Posted August 17, 2023 Share Posted August 17, 2023 I'm going to show my ignorance here. I fully get the benefit of providing better earths - I'll be doing the same when I drop the new engine in - but 35mm cable? Is that an inch and a half across, or 35 square mm? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 17, 2023 Share Posted August 17, 2023 53 minutes ago, Junglie said: but 35mm cable? Is that an inch and a half across, or 35 square mm? I'd assume 35 square mm, about 7mm (core) dia / ~11mm OD if google is to be believed. 1 1 Quote Link to comment Share on other sites More sharing options...
Junglie Posted August 17, 2023 Share Posted August 17, 2023 Yes, in hindsight that's obvious. Note to self - must not post after working all night... Quote Link to comment Share on other sites More sharing options...
Troll Hunter Posted August 21, 2023 Share Posted August 21, 2023 I'm attempting to avoid the bad earth syndrome by providing every consumer (lights, indicators, fans) with its own earth to an earth busbar. Each busbar has a cable to the battery negative. Will it work, I'll tell you in some twenty years time. PS. I'm just gone 80 yrs old! 😄 1 Quote Link to comment Share on other sites More sharing options...
Stellaghost Posted August 21, 2023 Share Posted August 21, 2023 10 minutes ago, Troll Hunter said: PS. I'm just gone 80 yrs old! 😄 Wow, 80 and still tinkering... Hope that's me in another 20 years Regards Stephen Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 21, 2023 Share Posted August 21, 2023 2 hours ago, Troll Hunter said: I'm attempting to avoid the bad earth syndrome by providing every consumer (lights, indicators, fans) with its own earth to an earth busbar. Each busbar has a cable to the battery negative. Will it work, I'll tell you in some twenty years time. That's a lot of busbars! Quote Link to comment Share on other sites More sharing options...
monkie Posted August 21, 2023 Share Posted August 21, 2023 I have 5 bus bars for the earth points. 1 in each corner and one near the fuse box. A couple of years in and I've not had a return of the electrical issues caused by sloppy earthing. 1 Quote Link to comment Share on other sites More sharing options...
Peaklander Posted August 21, 2023 Share Posted August 21, 2023 There is an often missed earth point near the front of the transfer box. Look up from the propshaft flange. A bad connection here affected the fuel and water temperature gauges on my 300TDi Defender. Quote Link to comment Share on other sites More sharing options...
ped Posted August 22, 2023 Share Posted August 22, 2023 i have 3 main earths from the battery-or will have when i've finished building her 1 to one of the starter bolts 2 to the back of the gear box 3 to the chassis i may add others yet to the rear tub as i have so far only put provisions in for a chassis to tub earth Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 22, 2023 Share Posted August 22, 2023 19 minutes ago, ped said: 2 to the back of the gear box Curious about these, given the starter earth for starter / alternator / engine I'm not sure why the gearbox would need any extra? Quote Link to comment Share on other sites More sharing options...
ped Posted August 22, 2023 Share Posted August 22, 2023 That's where i used to earth it and i have a cable that fits it so i thought belt and braces I'll stick that on as well Quote Link to comment Share on other sites More sharing options...
pete3000 Posted August 27, 2023 Share Posted August 27, 2023 Re-doing the ones you have is also worth while. Don't rely on a crimp, fill with solder and cover with some glue lined heatshrink. Pete Quote Link to comment Share on other sites More sharing options...
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