[allen smith]

Fixed the problem, a bad light switch, and thanks. Everything working on the car, but the horn.
As noted earlier, previous owner said he replaced all wires from a 1972, including the dash, intermediate, engine, front lights. I did replace the front with a new correct `70. Now I am unsure if the horn should work OK, and I hear a clicking at the steering wheel when pressing the horn, which was the case PRIOR to replacing with the new harness. The new harness has two connectors for the relay that WAS on the firewall. The current relay is somewhere under the dash from a `72. I have several relays in the garage from a `69 & `70. Should my horn work without the two firewall relay plug ins, or do I simply mount one of my `70 relays and the 2 plug ins? Again, prior to changing the harness the horns were not operating, and they are original. I would really like to see a `72 relay and understand what wire does what, and where it goes. thanks

[robz]

Originally Posted by allen smith

Fixed the problem, a bad light switch, and thanks. Everything working on the car, but the horn.
As noted earlier, previous owner said he replaced all wires from a 1972, including the dash, intermediate, engine, front lights. I did replace the front with a new correct `70. Now I am unsure if the horn should work OK, and I hear a clicking at the steering wheel when pressing the horn, which was the case PRIOR to replacing with the new harness. The new harness has two connectors for the relay that WAS on the firewall. The current relay is somewhere under the dash from a `72. I have several relays in the garage from a `69 & `70. Should my horn work without the two firewall relay plug ins, or do I simply mount one of my `70 relays and the 2 plug ins? Again, prior to changing the harness the horns were not operating, and they are original. I would really like to see a `72 relay and understand what wire does what, and where it goes. thanks

Glad to hear you resolved one of your gremlins...As for the horn, simple test:

Try isolating horn, by unplugging it and feeding it a 12v source directly along with a good ground...if it works, diagnose backwards in harness/relay...

[allen smith]

For some strange reason my park light fuse is blowing again. Strangest thing I ever saw. Just out of the blue it started doing it again. Ive unplugged from the fuse block my aftermarket radio, hood tach, and it still does it. No rhyme or reason to me. I replaced the switch a while back and cured it. Surely the switch has not gone bad already?

[allen smith]

Just picked up an "Auto Zone" switch, life time warranty, but before I plug in my 3 accessory wires to the fuse block, does it matter which side of the block, left or right? For instance, the park light fuse is on the left side and the radio is on the right side. Also should they all 3 be placed into the same fuse location, such as "RADIO"? The 3 wires I have are for the aftermarket radio and one is for a CD changer. Also wondering if it matters which side (left or right) of the fuse end they are plugged into, if the "RADIO" designated fuse is used?

["QUICK-SILVER"]

You said you have three wires but only listed two accessories.

Where you put them depends on what kind of power supply you need. Hot all the time or hot with switch on.

'Generally' speaking one side of the fuse box is hot at all times and the other hot with ignition switch on.
Need to pull a fuse out and see which fuse clip is hot from switch (or battery) and which side goes out to it's respective component. If "your" accessory wires have in-line fuses....you can hook to the hot side of the fuse in box. If it needs to be protected by the fuse box....hook to the other end of the fuse. So power goes through the fuse before going out to accessories.

Headlight switch going bad was an odd ball first time around. It'ld really be odd if it's happened again.

Inspect the connector/plug-in to the headlight switch for melted/hot spots that might be letting terminals touch.

Not sure what else to say now.
Definitely keep us updated with whatever you find.
Good Luck

[allen smith]

Now I notice with those 3 accessory wires (radio, CD changer) unplugged it still blows the park light fuse. Thinking about unplugging the forward wire harness as Ive already checked the forward connectors. If I unplug the forward harness at the fuse block and then no fuse blows when the switch is turned on that would mean the trouble is somewhere in the forward harness???

[robz]

Allen, I had a similar things years ago on my H/T...Whenever I turned on parking lights, fuse blew...After many tests/visual inspections under dash, ended up being my front light harness had one wire (parking light)crimped under fender/rad support with a few strands sticking through and shorting out...Very hard to see unless you pull out harness and inspect thoroughly under good lighting... Try isolating front/back parking lights and test to see which side problem comes from and work from there...

[allen smith]

I went out to the garage this morning and unplugged the front light harness, and still blows the fuse. So I then unplugged the rear light harness in the trunk, and still blows the fuse. Now Im thinking this short or wire break probably in the dash area.

This whole problem originated when the car came back from the body shop back in the spring. My carpet and interior stayed in tact. My theory is they let a mouse get to my dash, based on the scenario there at the shop. Whats so strange is that after I replaced the headlight/ park switch several months ago, the problem was resolved. I did replace another switch over this past weekend, and even did it twice, just incase I got a new "bad" one.

I assume there is a way someone with electrical experience can isolate the problem, and without removing the dash? Trace the wires one by one from the switch??

[robz]

Seem to recall from earlier posts/thread that the dimmer switch supplies 12v to headlight switch, but that may be only for the headlights and not parking lights...Your headlights work fine, right? Just a thought if you have a spare dimmer switch (unless someone chimes in that it shouldn't affect the parking lights)...

[allen smith]

Yes robz, the headlights work fine. I wish I had the experience to locate the short which now appears to be within the dash or intermediate harness. A friend called me this morning and said he had this problem yrs ago with a `70 Nova and discovered a break near the heal pad area (under the brake and accelerator) under the carpet, in the intermediate harness. Thanks for any additional advice, as Im still scratching my head on this one. How hard is it to test and I assume you can test from the wires going into the switch??

[LPete]

What I do is substitute a lamp for the fuse (I use a headlamp with leads on it). When the short is occurring the lamp is very bright; when the short is gone the lamp goes dim. This allows me to wiggle wires and disconnect connectors while watching the lamp -- it's very apparent when the short is gone.

[allen smith]

Thanks LPete, so if I attach the terminals of a spare headlamp to each end of the park light fuse, to make the connection then I can do as you stated and wiggle wires until the light brightness flickers or goes dim. Is there any chance of burning up wires doing this with the fuse out and a headlight in its place?

[LPete]

No chance, as long as you don't short across the fuse terminals accidentally. The short basically becomes the switch in the circuit, with the lamp as a load. When you turn the "switch" off, the lamp goes dim (doesn't go out, because you still have current flowing in the circuit).

[allen smith]

Im going to give this a try this weekend. Ive just been scared to death of burning up wires. Im totally out of the understanding on electrical issues, so as long as it's a headlight Im using and I dont let the terminals touch each other, then no over heating / melting wires.

[LPete]

Originally Posted by allen smith

Im going to give this a try this weekend. Ive just been scared to death of burning up wires. Im totally out of the understanding on electrical issues, so as long as it's a headlight Im using and I dont let the terminals touch each other, then no over heating / melting wires.

That's correct. The headlight acts as a resistor that limits current flow in the circuit. You could use a lower-wattage bulb -- I like a headlight because I can aim it at the ceiling and see it from all over the car.

[robz]

Or use a horn if that's easier...but it may shock you every time it goes off...LOL!

[wytnyt]

nothing more irritating than fuses blowing
dam qu.eer electrodes

[allen smith]

Just started my initial test, but when I turned on the switch the headlight i was using for a tester blew immediately. It was wired up very cautiously with all wiring kept seperate at both ends, wires kept seperate and taped off at the fuse block too. I used an old T3 lamp that I tested off the battery and it worked fine.

Before I procede, should I have used a halogen?

["QUICK-SILVER"]

It was just time for the old bulb to go.
A plain old 12 volt test light has always worked fine for me, for this kind of testing.
Front and rear harnesses need unplugged (or all bulbs removed). Then probe wires individually at the headlight switch to see which one is shorted to ground. You could also use your multi meter and check resistance to ground on each wire.
Front and rear tail light/park light feed wires, and the dash light wire going to fuse box are what need tested.
Need to narrow it down to one wire then start looking for where the actual short is.

[allen smith]

So without the tail light harness unplugged and front park light bulbs removed, then use a test light from what each wire at headlight switch? So is this possible without the fuse in place? With a new fuse in place it blows immediately upon turning on.