Voltage drop

[saildrive2001]

I was looking to find why my air horns don't always work & started to check the voltage at various places. When I check the voltage at the starter solenoid & then check the voltage at the fuses I am getting a 1 volt drop. The harness was replaced 10 years ago when I did the rebuild. I would really like to check the voltage at the ignition switch but can't get to it without partially removing the dash. I was wondering if any of you are getting the same voltage drop?

[rgh0]

The ignition switch is marginal in its capacity ot handle the original loads imposed on it when new. Corrosion and dirt on the contacts inside the swtich can cause a signficant voltage drop when loads are applied in the circuits it switches. And as you observe removing it for cleaning or replacement is not a trivial exercise

When I redesigned the wiring on my Elan many years ago i added relays for the horn and other loads so the ignition switch is just carrying current for the relays it controls.

Recently i have added a relay for the preengage starter which I change to after i did the re wiring. The current drawn by the preengage solenoid on the starter is around 10 amps which is to much for the igntion switch directly.

cheers
Rohan

[saildrive2001]

I have had air horns on my car almost from new & they use a relay. The problem is that even using a relay the power to the relay comes through the ignition switch & the fuse. The relay only means the horn button carries a small current to activate it. If you look at the circuit diagram almost everything comes through the fuses & the ignition switch. I should have checked the ignition switch when I did the restoration, a good point for anyone doing a rebuild to check.