LMTV - Brake lights stopped working (Troubleshooing) Follow-Along

[j_boucher]

So I checked the K10 86 and 85 and 86 does have 12V when the pedal pushed / relay clicks as well when installed .

 

[Ronmar]

in the drawing I attached that same 12v should also be on k10 pin 87 and is what feeds thru the relay to pin 30 when k10 energizes, to light the brake lights. it may be you have a bad connection somewhere along the source path from K6. it delivers measurable voltage unloaded and enough current to energize k10, but not enough to light the rear lights like the flasher does. IE: voltage is not good until it measures good under load.

You can wrap a small bare wire around K10-30 that sticks out from under the relay far enough to sample the voltage of the intact circuit when you step on the pedal with the normal load applied. What does that voltage look like?

You can also do the same bare wire test to measure voltage on the loaded circuit at K6-87 and D-1A... This might show where the circuit is breaking down and not flowing enough current to maintain full voltage under load.

 

[j_boucher]

in the drawing I attached that same 12v should also be on k10 pin 87 and is what feeds thru the relay to pin 30 when k10 energizes, to light the brake lights. it may be you have a bad connection somewhere along the source path from K6. it delivers measurable voltage unloaded and enough current to energize k10, but not enough to light the rear lights like the flasher does. IE: voltage is not good until it measures good under load.

You can wrap a small bare wire around K10-30 that sticks out from under the relay far enough to sample the voltage of the intact circuit when you step on the pedal with the normal load applied. What does that voltage look like?

You can also do the same bare wire test to measure voltage on the loaded circuit at K6-87 and D-1A... This might show where the circuit is breaking down and not flowing enough current to maintain full voltage under load.

So again you show you are the master , I tested K10 87 12.2 volts then tested K10 30 … zero volts although it clicked no voltage to PIn 30 swapped in a new relay and bingo K10 30 had 12.2 volts and my brake lights work again. I ordered some bosh relays both 12 and 24v and fuses going to start swapping them out this week . Thanks again for your wisdom greatly appreciated

 

[Ronmar]

Wow, an actual bad relay! Cool, that doesn’t happen very often