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Old 7th July 2020, 10:18   #11
SD1too
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Quote:
Originally Posted by raykay View Post
As I read post 4, the switch contacts were 'bridged', rather than connected to Earth.
Ah, thanks for pointing that out Ray. I was going by Harry's preceding post no. 3 but you are right.

So as I understand it James, the LH reversing lamp from C0296-17 works but the RH (from C0286-15) doesn't. You say the earth connection is shared by both.

When you're measuring the voltage at pin 15 with bulb fitted (0v) and removed (12v), is the voltage at pin 17 (LH bulb) constantly 12v?

Please continue to use your voltmeter for this test.

Simon
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Old 7th July 2020, 11:31   #12
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Think i've made progress today.

Removed the glovebox again for access to K109. Connected a test bulb to pin 19, gearbox into reverse and ignition on. Not a flicker.

Bridged the reverse switch connections and repeated test. Bingo we have light.
Tested again with switch removed and connected, nothing.
Removed the switch and cleaned the plunger, again testing it off the car and it worked. Back in the car nothing happening.

So i'll change the switch and see if that improves things

Thanks all for the advise, every day's a school day
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Old 7th July 2020, 12:17   #13
SD1too
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Removed the switch and cleaned the plunger, again testing it off the car and it worked. Back in the car nothing happening.
So i'll change the switch and see if that improves things.
James,

If the switch worked off the car, how will buying a new one help?

Simon
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Old 7th July 2020, 12:58   #14
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As in post 3, "The switch in the manual car is a common problem - it works fine if you remove it and test it, but putting the car in reverse, the switch is often not pushed hard/far enough to put the lights on."
A replacement switch may cure the problem.
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Old 7th July 2020, 13:09   #15
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Quote:
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Bridged the reverse switch connections and repeated test. Bingo we have light.
Check if the reversing lights work if you bridge the switch, if they do, you may have found the cause of the problem.
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Old 7th July 2020, 15:49   #16
HarryM1BYT
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Originally Posted by SD1too View Post
James,

If the switch worked off the car, how will buying a new one help?

Simon
The switch plungers are not thrown or pushed far enough, when reverse is selected. Maybe a combination of wear of the gearbox and wear in the original switch. A new switch, adding a blob of solder to the nose of the plunger or turning the hex down in a lathe can all help fix the problem.
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Old 10th July 2020, 10:47   #17
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All,

Managed to fix the reverse light problem. It was the switch after all. The old one must have been been playing tricks with the circuit and tests I tried. Electrickery can be challenging at times.

Interestingly the new switch from plunger tip to nut is slightly shorter than the original.

Big thanks to all that helped, and its another example of switch failure to add to the list
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Old 10th July 2020, 19:53   #18
HarryM1BYT
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Quote:
Originally Posted by jwykes View Post
All,

Managed to fix the reverse light problem. It was the switch after all. The old one must have been been playing tricks with the circuit and tests I tried. Electrickery can be challenging at times.

Interestingly the new switch from plunger tip to nut is slightly shorter than the original.

Big thanks to all that helped, and its another example of switch failure to add to the list
Post #3, above

The new switch will operate with the plunger further out, than the old one.
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Fix a poor handbrake; DIY ABS diagnostic unit; Loan of the spanner needed to change the CDT belts; free OBD diagnostics +MAF; Correct Bosch MAF cheap; DVB-T install in an ex-hi-line system; DD install with a HK amp; FBH servicing.

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