[dataway]

I just did a full power bench test of my entire dash harness and new engine and AC harness to check for hot spots and make sure all the dash lights were working.

While it was operating I kept an eye on voltage, total amps and amps through the various components. Of particular concern to me was the blower motor harness since mine, and so many originals show signs of burning up.

If anyone is curious the decent condition OEM blower motor draws 8-9 amps on low, and 22-23 amps on high. The Master Relay which energizes the blower motor is itself energized by the Master Switch .. which is a reed switch with two connections on the AC/Heat control head. What become obvious is that if the blower speed switch is on high, the Master Relay is switching about 23 amps, if the blower speed switch is on low the Master Relay is only switching about 9 amps. It occurred to me that it would be very good practice for me, and probably anyone with a 68, to make sure they always start the AC/Heat/Defrost etc. in LOW speed, then move it to high speed after the motor is running.

If you leave the speed switch in HIGH, then every time you slide the right hand vertical slider up from the OFF position it's going to cause the Master Relay to switch the maximum 23 amps. Which can't be good for the contacts I wouldn't think on an old OEM relay.

Anyway, not sure if anyone cares, but it could probably increase the life of the Master Relay considerably. Also, I have no idea if this same situation applies to 69 cars since quite a few changes were behind the dash that year.

Total amp draw with dash lights on (LED), blower motor on high and cigarette light pushed in was about 30-31 amps. That's all I could really hook up on the bench at this point. Throw in a full set of incandescent taillights, headlights, AC clutch engaged, radio blasting and jeez, quite the load on the alternator ( I'll be running LED headlights and taillights).