I have been working on a freinds 66 impala....sorry not chevelle this time but close.ive been jumping back and forth from different projects. i just have a few questions. i have upgraded to a internal regulated alternator 3 wire. ( one wire to horn relay, one to dummy light and one to power for voltage sensing) i also swapped a 350 trans into it. the problem is that sometimes the car starts and everything is cool. but somtimes its completly dead? no power at fuse box horn relay, no lights ect.....it was getting late and not enogh time to look at every thing but i was thinking if it were a fusable link, it would not come on and off every so often.so i think it has to be between the horn relay and the neutral saftey switch....is there a way to test horn relay? also what about a way to eliminate or upgrade the neutral saftey switch. the one on it now is from a pgtrans. now its got th350. what do you guys think.
any suggestions would be appreciated. thanks

The horn relay only acts as a junction point for the wires. It could be melted inside and the car would start. A better place to check if power is coming inside the car would be the BAT terminal on the fuseblock.

Neutral safety switch shouldn't cause "no lights" since it only iterrupts the power to the starter's "S" terminal.

ok thanks guys i will let you know what i find out in next couple of days if weather permits... thanks again