A new electrical problem most of us have

[danno 128]

I think I am probably the first to announce I discovered a new problem that I think most of us have.  Maybe I have not discovered it, but at least  I am revealing it.

 

The problem is that when the car is running (or not), and the heater is on fast speed or the AC is on, the turn signals slow way down, if not stop.  I have noticed this before, but in a convertible I do not need the fan on that much.   It was worse this fall when I had to run the heater.   I turn the fan on high speed, and the turn signals slow way down.

 

The problem is the same as the headlight issue and why you need the headlight relay to get brighter lights.  When the blower is on at high speed, it takes about 14 amps.  The resistance in the wires and connectors from the battery to the ACCY side of the ignition switch is so high that the voltage is much lower when it gets to the turn signal lights. I measured about 13.4 volts on my battery when the motor is running ( which is a bit low), and 13.0 volts on the ACCY wire when the fan is off.  I turn the fan on to high speed, and the voltage at ACCY drops to 12.0 volts. It drops a bit more to the turn signals, so they slow down a noticeable amount. So I have a high resistance in the wires and connections, the drop of 1.4 volts for about 18 amps is just under 0.1 ohm.

 

The solution is to either increase the voltage to the battery when the car is running, or clean all the wire contacts, or install a relay for the heater and AC like we do on the headlights.

 

Those of us with aftermarket wire harnesses will not see this problem. It could be worse for those of us without the headlight on relay, but maybe not?

 

Who else has this problem?

[Midlife 814]

Unfortunately, the turn signal switch power derives from the headlight switch, which is tied into the BAT side of the fuse box, not the ACCY side.  However, you have correctly diagnosed the issue: high current draw on the system drains the voltage level at the battery and thus all other systems.  Your alternator should accommodate the voltage drop by constantly feeding in 14.5V or so to the battery.  You probably have higher resistance throughout your system than normal: probably corroded contacts or poorly crimped pins.