Is there any way to prevent the headlights from drawing power away from the wipers and signals? They both work well until I turn the headlights on, then they slow down considerably. I have installed new wiring harnesses for the headlights and the rear wiring harness for the tail lights etc. I also installed a higher amp alternator hoping that would help out. My car is a 67 Chevelle with a big block and 4 spd. Thanx for any help!

Rick

Sounds like grounds...or poor connections on the horn relay or bad cable connection to the battery or the + post behind the battery,,,

Ron

All the connections are solid...could an old (read original) horn relay be the cause?

If all the connections are good relays on the lights would help a lot. They're not that much money and easy enough to install.

Thanx 540, could you point me in the right direction as to where I can get these relays?

Something is broke there. The old 37 amp alternators could easily handle lights, wipers, and heater motor from idle to whatever rpms the engine could turn. If yours doesn't, then look at whatever might have been "modified", "improved", or "updated". Put things back to the way the intelligent GM designers made it and it will work if you get it original and FIXED.

Relays on the lights will make things even worse as they allow the lights to draw as much current as they are capable of. That will slow you down even worse.

Something is not right,,,I'll give ya that, but the only "improved" piece is the higher amp alternator, I don't think that is causing the problem. The wiring harnesses and voltage regulator stock replacements. I'll nail it down...just gonna take a little more digging.

if you use a meter between each piece,turn one on at a time and check the voltage drop between each, the one with the higher voltage drop is probably your problem

thanx Curt...that was the direction i was headed. will post results when i get them.

I had to think this problem over for half-a-second, but you need to look at what the common link is here for items that create a 'noticable' effect when they operate, since these items will draw a little current when they are on. Headlights draw a 'high' amount of current compared to some other electrical items (the starter being the largest), but they all have to have a common 'ground' link from the battery. I would start from the negative side of the battery post to where it gets grounded to the frame or however many ground connections that are being made from the negative post, you need to look for a 'voltage drop' across a connection when these high-current devices are in use. The poor continuity of a connection will show up as a 'voltage drop' when current passes through the 'suspect' connection.
Case in point: I had to deal with someone's car that would not crank, but everything else was working fine (headlights included). Before I even bothered to bring out the jumper cables, all I did was clamp a vise grip onto one of the battery post connection that looked suspicious, and it kicked right over. The battery clamp was simply a little loose but could not be tightened down onto the post anymore & needed replacement. The starter needed the current, but the connection could not handle it, just simple case of poor continuity.
The higher the voltage drop, the poorer the continuity.

thanx JW, i'll definitely follow up on that. at the very least...it will eliminate any possiblity of loose connections.