Front Turn Signal 356C

[James Learmonth]

I have replaced the left front turn signal and park light assembly to correct a front left turn that didn't signal. After reassembly the left front park light is inop. The left tail light and right license plate light are also out. Fuse No.8 is blown. Checked the wiring and have found no obvious shorts. Must go to Autozone and renew my supply of fuses. Many trials and errors have used up all my spares. Turn signal works as advertised but not the left side park and tail lights. Any thoughts on what I have missed here? Help!!!!

Jim Learmonth
1965 356C
Houston, TX

[Jeffrey Leeds]

The usual best place to start with 98% of electrical problems is bad ground(s). Whenever I am doing anything electrical I try to attach every ground wire with a star washer under the bolt or screw head in the expectation that the washer serrations will get a better bite than a common flat washer.

Jeff

[Sebastian Gaeta]

Jim,

Besides Jeff's great advice on grounds (which it will probably end up being the culprit), also check the bullet connectors from the wires coming off of the turn signal switch that go into the junction block under the dashboard. If any of these are not well connected, you will run into issues like this.

[Jeffrey Leeds]

Thanks Sebastian.

I'd add one thing thing to your recommendation. More and more I'm using a product called Deoxit D (Amazon and other's) especially for bullet type connectors and grounds. No affiliation - just satisfactory experiences.

Jeff

[Jim Alton]

Your description of the problem begs some questions. Does the # 8 fuse blow every time you replace it or did you blow your last fuse and stop?

Blowing a fuse takes a lot of current--that pretty much has to be a short circuit.

Intermittent Short
One likely cause: you had the circuit energized while installing the turn signal and the hot wire/connector touched ground, shorting the circuit and blowing the fuse. If that's the case, you just need to replace the fuse.

Defective Turn Signal Unit or Bulb
Maybe there's some defect in the turn signal unit or light bulb causing a short circuit. I know you inspected everything and didn't see an obvious short but maybe it's not obvious.

You might put an ohmmeter across the terminals of the turn signal unit. Without a bulb you should see an open circuit i.e. ∞Ω. A very low resistance implies a bad turn signal unit.

With the bulb in place you should see low resistances. A 21 watt 6 volt filament would be about 1.7 Ω and a 10 watt 6 volt filament should be about 3.6 Ω. Ohmmeters aren't usually accurate at these low resistances but a difference between 0 Ω and these values should be apparent.