Hello; I bought my 69 conv last year and the horn and wipers do not work. Any suggestions on the best way to isolate the problem? An electrician suggested I start off by replacing the wiper motor first....

Thank You,

First get a test lamp and download the wiring diagrams. Then test the wiper motor wires. Do you have power there?

If so, the next thing you could do is remove the wiper motor, use test leads and wire it directly to the battery. If it does not work, then look into replacing it.

Do the same for the horns. Start backwards by wiring the horns directly to the battery to see if they work. Then test for power at the horns, then the horn relay.

jms, yes get a test lamp or VOM (voltage ohm meter). the first place to look is the fuse block. Make sure that you have voltage at the fuse, then turn the ignition switch and wiper switch on. Then test to see if you have voltage at the wiper motor connection.

Sal described the way to check the horns. Let us know if ya get stuck on anything.

I can tell you the usual suspects with these two accessories;
With the horn it's usually the relay or hotwiring was attempted, or both.
With the wipers, and particularly on a 69, the switch is touchy. Half the 9's I've owned have had bad switches and the other half have had touchy switches. It's a defective part.