Pete Lewis Posted June 9, 2022 Report Share Posted June 9, 2022 nah i would sooner have a coffee or drive the car in the sun we have enough problems at 21 you need to know why at 76 you just need to fix it ha ! Pete Link to comment Share on other sites More sharing options...
Chris A Posted June 9, 2022 Author Report Share Posted June 9, 2022 1 hour ago, cliff.b said: I think this has got past the point of fixing it now and into the realms of trying to understand why it's doing it lol 49 minutes ago, johny said: yes we want a definite fix as it may come back to bite again but trouble is if Chris runs a new wire we will never know if the problem was an earth fault or induced current😭 That is where I am as well, I like to know 'why' in general and hopefully understand. If all goes to plan I should have the time later this afternoon to have another look at it in 3 steps. 1. Careful inspection under the dashboard for any faulty wires. 2. Fit a filament bulb in place of the LED. 3. Make a test lead with a bulb and run it a live feed (probably the battery) via the bulb ( if I can find my old soldering iron & solder in my 'archives' to the sensor. I will of course report back. Watch this space. Thanks to all for the help & suggestions A bientôt Link to comment Share on other sites More sharing options...
Chris A Posted June 9, 2022 Author Report Share Posted June 9, 2022 1 minute ago, Pete Lewis said: nah i would sooner have a coffee or drive the car in the sun we have enough problems at 21 you need to know why at 76 you just need to fix it ha ! Pete Well, I'm aged between 21 and 76 so I will have that coffee then go for a drive in the sun and on return fix it ( I hope) or ignore it. Link to comment Share on other sites More sharing options...
cliff.b Posted June 9, 2022 Report Share Posted June 9, 2022 1 hour ago, NonMember said: Yes, which is why I queried the capacitance issue. If you induce voltage in a wire then it appears at the free end, not the bulb. Actually, you don't "induce" voltage, you induce current. You can get voltage from capacitive coupling, and the induced current can flow as long as there's somewhere for the charge to collect - i.e. a capacitance. Rather like you, I instinctively don't think this explanation holds water. However, stray capacitance and inductance are the bane of many a sensitive electronic circuit and LED bulbs are potentially quite sensitive. Ok, I felt compelled to carry out a bit of testing on my own car. I connected one lead of my meter to the +ve terminal of the battery and the other to a random spare length of wire, connected to nothing. The meter showed a background reading of about 0.005v I then started the engine and the meter was reading 0.3v to 0.5v depending where I placed the wire (near HT leads was highest) and how fast the engine was running. I then connected an led bulb (12v but not a car one) across the meter terminals, so I now had an led connected by one terminal to the battery, the other terminal to a loose piece of wire and a meter across it which was now showing about 0.05v I started the engine again, repeated my wire waggling and was now seeing up to nearly 6v on the meter. The led did not flicker that I could see, but clearly there is a potential difference here and the behaviour may be down to the individual led behaviour. Interested in thoughts/explanations🤔 1 Link to comment Share on other sites More sharing options...
Chris A Posted June 9, 2022 Author Report Share Posted June 9, 2022 1 hour ago, cliff.b said: I started the engine again, repeated my wire waggling and was now seeing up to nearly 6v on the meter. The led did not flicker that I could see, but clearly there is a potential difference here and the behaviour may be down to the individual led behaviour. Interesting. When I tried 2 leds with different power consumption I did get the flicker, although the lower rated bulb was less visible, as would be expected. Lunch break nearly over so I'll soon be able to go and have another look. I'll report back at tea break time. Oh, yes been here nearly 30 years and still have a tea break in the afternoon, some habits can't/shouldn't be broken. Link to comment Share on other sites More sharing options...
cliff.b Posted June 9, 2022 Report Share Posted June 9, 2022 25 minutes ago, Chris A said: Interesting. When I tried 2 leds with different power consumption I did get the flicker, although the lower rated bulb was less visible, as would be expected. Lunch break nearly over so I'll soon be able to go and have another look. I'll report back at tea break time. Oh, yes been here nearly 30 years and still have a tea break in the afternoon, some habits can't/shouldn't be broken. Would be interesting to connect your most flickering led in the same way that I did and if it still flickers, I think that would probably prove that it's not a fault with the existing wiring. Probably wouldn't need to solder anything, just strip an inch of insulation off the spare bit of wire and wrap around the thread of the led bulb, then hold the centre contact against the battery +ve terminal. Your free hand then free to waggle the dangly wire about. Link to comment Share on other sites More sharing options...
Chris A Posted June 9, 2022 Author Report Share Posted June 9, 2022 4 hours ago, Chris A said: If all goes to plan I should have the time later this afternoon to have another look at it in 3 steps. 1. Careful inspection under the dashboard for any faulty wires. 2. Fit a filament bulb in place of the LED. 3. Make a test lead with a bulb and run it a live feed (probably the battery) via the bulb ( if I can find my old soldering iron & solder in my 'archives' to the sensor. Right then, 1. nothing untoward, other than a bit of a mess that could do with a tidy up. 2. Before trying a filament bulb I got the engine running and the oil pressure up to the light going off. Blipping the accelerator didn't get the led to flicker. So went to make a test wire and bulb, which will always come in handy. On return started car and this time gave it some real heavy foot, it did flicker. Fitted a filament bulb that was tested to be 100% sure it worked. No flicker! (I can hear Mr Lewis laughing 'I told you so'). Refitted led flickering returned. 3. Used the test wire which was fitted with a led connected to battery and all the wire and bulb placed on top of the coil. Yes I did make sure it was connected the right way round and not 'back to front' Ran engine and reached across to the carb to give it some welly. No flicker! Fitted filament bulb and went for a run 'round the block', all as it should be as far as I could see. For the time being I'll stick with the normal bulb even though I would like something brighter. When I get bored and have nothing else to do (what really?) I might make up a replacement wire with a led and run it well away from the coil, ht cables etc to see what happens. Thanks to all for your thoughts and suggestions I would have liked to have been able to find a 100% sure reason for the effect. Link to comment Share on other sites More sharing options...
johny Posted June 9, 2022 Report Share Posted June 9, 2022 oh dear as you say still not sure its conclusive because a high resistance earth fault on the wire from the LED could cause it to flicker but not pass enough current to do the same to a filament bulb! Pity you couldnt get the same effect with the test wire and LED😖 Link to comment Share on other sites More sharing options...
Wagger Posted June 9, 2022 Report Share Posted June 9, 2022 Actually, you have foiund the reason. It is called Radio Frequency Interference, or Electro Magnetic Interference. RFI and EMI. It cannot be seen until it lights something up! Fitting even more suppressors can reduce it, but why bother when filament bulbs do not show it up. Just worry when they never light up. Link to comment Share on other sites More sharing options...
Wagger Posted June 9, 2022 Report Share Posted June 9, 2022 A pal once had his bonnet open with the engine running. His radio was crackling awfully and he was trying to tune it and adjust the matching device for the antenna, add suppressors etc. I shut his bonnet, all interference stopped. He'd wasted a whole dinner break before I turned up. A similar phenomena, also invisible. I'd not skipped my lunch. Link to comment Share on other sites More sharing options...
cliff.b Posted June 9, 2022 Report Share Posted June 9, 2022 18 minutes ago, johny said: oh dear as you say still not sure its conclusive because a high resistance earth fault on the wire from the LED could cause it to flicker but not pass enough current to do the same to a filament bulb! Pity you couldnt get the same effect with the test wire and LED😖 Yes, unless it flickers on a new circuit I don't think it will be possible to conclusively prove the cause. Which is frustrating but fortunately doesn't really matter lol 1 Link to comment Share on other sites More sharing options...
Chris A Posted June 30, 2022 Author Report Share Posted June 30, 2022 Well at long last I have replaced the cable from the pressure sensor to the warning light. The order I was waiting for finally arrived once the out of stock item was received by the supplier. The result is : No flicker with a LED. Not when the car is stationary at least, it did flicker before when stationary. The real proof will be when I get to take it for a proper run. That could be tomorrow or failing that won't be until at least Tuesday of next week, I have to prepare for a big event this weekend - no not the Classic Le Mans happening an hour away from me but taking Mrs. to the far opposite end of the department for her 3 week thermal cure (3 weeks freedom for me also). I am quite pleased with myself as I de-soldered the old wire from the bulb holder and soldered in the new wire rather than just cut and fit a bullet connector or such. As I'm here, how tight should the pressure sensor be when done up? The one fitted is very tight! I have a higher pressure sensor that I want to fit - so I get to see the bright green light a bit longer on starting the engine 😁 Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 30, 2022 Report Share Posted June 30, 2022 just hand tight with the appropriate spanner no gorilla fingers needed Pete Link to comment Share on other sites More sharing options...
Chris A Posted June 30, 2022 Author Report Share Posted June 30, 2022 34 minutes ago, Pete Lewis said: just hand tight with the appropriate spanner no gorilla fingers needed Pete In that case it must have been tightened by a very big gorilla! The one fitted needs a 1/2" spanner and I couldn't move it with normal pressure on it. Can't use a ring spanner or socket due to design and situation. So double rations of spinach next week. Link to comment Share on other sites More sharing options...
cliff.b Posted June 30, 2022 Report Share Posted June 30, 2022 3 hours ago, Chris A said: Well at long last I have replaced the cable from the pressure sensor to the warning light. The order I was waiting for finally arrived once the out of stock item was received by the supplier. The result is : No flicker with a LED. Not when the car is stationary at least, it did flicker before when stationary. The real proof will be when I get to take it for a proper run. That could be tomorrow or failing that won't be until at least Tuesday of next week, I have to prepare for a big event this weekend - no not the Classic Le Mans happening an hour away from me but taking Mrs. to the far opposite end of the department for her 3 week thermal cure (3 weeks freedom for me also). I am quite pleased with myself as I de-soldered the old wire from the bulb holder and soldered in the new wire rather than just cut and fit a bullet connector or such. As I'm here, how tight should the pressure sensor be when done up? The one fitted is very tight! I have a higher pressure sensor that I want to fit - so I get to see the bright green light a bit longer on starting the engine 😁 Glad the plan appears to have worked 👍 Link to comment Share on other sites More sharing options...
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