KC John

I finished installing my new harness and dash. I was going to ask on this forum if there was any way to test that everything worked before I put everything back together. I was too anxious to wait and finished up, then cleaned up and put everything away. Then I hooked up the battery to test out my lights and they came right on, then the warning light for the lights stated to blink, so far so good. Next I turned on the radio and it was fine so I tried the blower on the heater and both speeds worked, but when I shut it off it continued to run on low. I had to giggle the **** back and forth to get it to go off. It looks like I might have to pull that apart and repair or replace it.

But then I tried the dash lights and the fuse for the dash blew, the one reason I decided to change out the harness and refurb the dash in the first place. I called tech support at LL and they told me I had a dead short (which I knew). He said I might have a power wire connected to ground or I might have a bad gauge that is back-feeding the circuit. I knew the Battery gauge didn't work before, but I was hoping it was because of the old harness. So I unplugged the gauge and tried again. Nope, blew the tail light fuse this time, but the dash fuse was not blown.

I knew my light switch was very old and thought it might be the problem. Did you ever take one of those apart? It explodes once you pull the two halves apart and it took me about 10 minutes to figure out how to get it all back together. I didn’t see anything fixable, so I bought a new one, installed it and still no dash lights.

I moved on checking things and my windshield wiper didn't work and it used to before I changed out the harness. It was so hard to get those 2 plugs in behind the distributor, I might have them on incorrectly because I had to do them blind. I’ll check that out tomorrow also.

I wish I found the short problem before I went through all the trouble of replacing the harness, but it really needed to be done anyway. The new harness wires are so short I don't know how you guys were able to install just the dash after the harness was already in the car. I hooked up everything on the bench and then installed the dash. That seemed to go very well, I only knocked one dash light out of the socket, but was able to reinstall it without any trouble.

Now I have no choice but to get out all the padding to make the floor level, remove the steering wheel and the driver's seat again. Then I can take my borescope (that I've owned for 3 years and have never found a use for it that was worth the trouble) and lay under the dash and video as much as I can to see if the problem is easy to spot.

I'm not sure why the tail light fuse blew out but the dash fuse didn’t, once I removed the plug from the Battery gauge. Sorry for this long post, but if anyone has any ideas of what I might have wrong, please save me from having to pull all the wires and dash out of the car again.

Revfan

My heart goes out to you man. Wish I had some suggestions... but I'm clueless here.

I'll follow along on our progress and hope for the best though!

Frankie the Fink

And through all that litany of woes you don't mention what year car you are working on ?

Revfan

Its not stated here... but I believe he has a '63 Vert

65GGvert

Do you have the normal bulbs, or led, or what?

KC John

Sorry for the lack of info. I have a '63 and I am using 1414 bulbs instead of 1816's.

DansYellow66

Have you replaced the entire harness throughout the car or only the dash harness?

buns

1414 bulbs draw .46 amps as opposed to the 1816 bulbs at .33 amps. .46 times 10 = 4.6 amps which is probably why you blew the 4 amp fuse. Another problem is that all the panel lamps are fed by a single 20 gauge wire which could easily fry if carrying too many amps.

65GGvert

Do you remember from your earlier thread that I told you the 4a fuse was barely enough to hold with the stock bulbs?

From post #5 in your thread titled "electrical?"

All it should take is 12v on the gray and ground on the cluster. I'm afraid when you get it all back together you'll find you'll blow the fuse because it was just barely rated high enough to carry the current to the dash lights and you just doubled the wattage multiplied by the number of bulbs.

tbarb

Also, just to add the original tail light and front parking bulbs are not #1157, they are #1034 which draw less amps.

thoyer

Pull all the fuses and measure from each fuse terminal to ground using an ohm meter. This may point you to the circuit giving you fits. Remember, bulbs have very low resistance so remove them as necessary to verify the wiring is not the issue.

Tom

cblankin

Take a look at this.

KC John

I disconnected the rear harness, my lighter and amp meter and I no longer blow the Lps fuse when I pull on the lights. The headlights come on and still no dash lights. I'd like to start installing things one at a time to see what kept blowing fuses, but I've gone through all my fuses.

Can a multimeter be used in some way to see if the fuse would blow if there was one without actually using a fuse?

As far as using an OHM meter to check things, I wouldn't know what to look for. I'm getting nervous about ever getting this thing to work.

65GGvert

I guess you don't believe me, so I'm out.

Frankie the Fink

There is a reason I never 'got in'...

KC John

I appreciate the help, but you assumed I was using a 4 amp fuse. I blew that fuse and was using a 20 amp fuse, so do you still stand by your comment.

I also pulled all but two 1414 bulbs and put back the 1816 bulbs and still blew the fuse. That is why I dismissed your post.

KC John

What is that supposed to mean?

thoyer

If you blew a 20 amp fuse then you are dealing with a direct short somewhere.

Based on the number of bulbs and the ratings that have been previously posted, the fuse should not blow instantaneously. Fuses are made to carry 100% of rated current for a long time. Their fusing performance is governed by what is called an i2t curve (I squared T - meaning current squared x time). Each fuse manufacturer has the curve available for each type of fuse. Running 4.6 amps through a 4 amp fuse will typically cause the fuse to blow around 10 seconds - see picture of a typical 3AG fuse below. (I'm not taking into account the inrush current of the cold lamps, which could be fairly significant, but still the 3Ag fuse should hold for some period of time. up to the rated fusing time)




Since you are blowing a 20 amp fuse, you have may have significant issue. Possibly a pinched wire or the insulation has been broken somewhere and the wire is touching ground or there is a mis-wire somewhere.

If you are not comfortable troubleshooting this further I would suggest you find someone that you trust to look into it.

If you have access to a 12 volt power supply that is current limited you may use that in place of the battery. You are only asking for trouble by using a battery to find a short...........

Tom

KC John

I do NOT have 12V at the bulb contact. I tested continuity from the pin on the gray wire to the contact of one bulb and it was good.

Then I hooked 12V to the pin for the gray wire and tested between the neg terminal on the battery and the metal on the dash and got 12V. As Tom mentioned, that means I have a dead short somewhere in the gray wire circuit. Right?

If so, I just can't find it.

This is how the dash is hooked up, does anyone see anything wrong?

IMG_0345 by awsum55, on Flickr

Jbabek

I have chased a lot of electrical gremlins, and find a Power Probe to be much more useful than a multi-meter. You can get one off of Amazon for about $70. I stumbled on this years ago when chasing two wires that had shorted together, but looked OK from the outside.

This will make it much easier to find the bad ground. The newer ones will also give a voltage reading, and let you know if you have a voltage 'leak', which can make all sorts of funny stuff happen.


Also, HEED TOMS ADVICE....hook to a power supply. A battery can do a lot of damage before you hear the sizzle, smell the smoke, or see the fire.