Park Tail fuse melting box?

[svwilbur]

Over the years I have seen far more wires,terminal blocks, etc. melted from loose connections than from overloads. Many pieces of equipment needed to have all of the connections tightened up after installing because either they did not get them tight at the factory or they loosened during shipping.

THIS IS CORRECT. LOCALIZED MELTING IS NOT A OVERLOAD PROBLEM......Put away your amp meters, what you need is an OHM meter or your fingers....LOL

When the circuit energized, just touch the different connection spots. If its localized "warm" you have a bad connection. If it hot you have a very bad connection.

so your saying the fuse did not blow because it did not short or overload, it had a bad connection and over headted?

but it over heated at the fuse so does that mean it had the bad connection at that side of the fuse connection rivet ?

or would it heat at the fuse from a bad connection at lets say a head light connector or a bad ground on the chassis near the park light in the rear?

would the bad frame ground in rear head up the fuse at that fuse connection?

[mraitch]

+1 in printing and laminating - had mine blown up to about 3' x 2' - then you can use dry erase markers to track wires.

[fj20spl311]

so your saying the fuse did not blow because it did not short or overload, it had a bad connection and over heated?.....CORRECT

it over heated at the fuse so does that mean it had the bad connection at that side of the fuse connection rivet ?......CORRET

Would it heat at the fuse from a bad connection at lets say a head light connector or a bad ground on the chassis near the park light in the rear?

would the bad frame ground in rear head up the fuse at that fuse connection?...NO...

It always overheats at the BAD CONNECTION

I THINK HE'S GOT IT.....

[jrusso07]

Heat came from poor connection at rivot where fuse clip mounts to buss bar on back side of fuse. Rivot is either loose or has corrosion in the joint. This causes arcing or high resistance (corrosion) which makes localized heat. (voltage x resistance = power, power = heat)


Bad ground would cause no light or dim light. It typically won't get warm because the frame acts like a heat sink.

In fuse box, there is no heat sinking except for the brass and brass transfers heat fast..and melts plastic.

[svwilbur]

STG switch is in the ignition and closes when key is inserted. Assuming buzzer and door switch are not disabled, when you open door with key in ignition, the buzzer sounds (don't leave key in ignition before you get out!).

Suspect fuse attempting to blow is due to heat, not due to short somewhere. Heat likely due to loose or corroded rivet as Phil suggest. Been there, done that.

I think fuse box cover is common to other Datsun models. My 510 had the same cover...think that is where the AC comes in to play.

I had a problem in my dimmer rheostat where the full on spot on the rheostat (read variable resistor) actually shorted it to ground and would cause the fuse to blow. The fact that your fuse isn't blowing likely means your circuit is ok. other indicators of bad circuit would be a dark, dim or bright light bulb as compared to others.

If you can't make measurements as suggested, you can chicken test with lower amp fuses. Start with an 8 amp or 10am and see if it blows. If not, suggest heat in rivot is the problem. Replace fuse box or wire in a in line type fuse for temporary fix.

You said "other indicators of bad circuit would be a dark, dim or bright light bulb as compared to others." I am assuming hou mean any light bulb in the circuit.

but one thing I have noticed is the head lights always seemed very dim. I assumed that was normal but maybe is an issue. both are equally dim. I can see them like when I drive into the garage to park it during the day. and I can see enough to drive at night but they are not like todays vehicles. and looking at them on in the sunlight you can hardly tell they are ON. is that normal for a roadster?

I may be afraid to disconnect that connection on the headlight as those seem to be prone to failure, connections got brittle on my older 57 chevy truck (for it I was able to buy a complete new reproduction wire harness for a couple hundred dollars and just replaced it all, it had real hard wiring and brittle connectors everywhere, which is why I replaced it. that and fear of a wire fire. never had any melting issues though.

[svwilbur]

I might get to this project later this afternoon. I have to finish my tach pinion project, try to lube tach cable and change my oil filter and refill oil before moving on to this wiring issue. and for the wirering issure (melted cuse box) I need to search my datsun parts stash for another fuse box and cover, that will take a while as it is "orga ized" all over the garage shelves in tuberware boxes that I have to look into to see if it is there. I have about 20 datsun ones. if I find it, I think I have two from my memory but I may be imagining it, then I can inspect it for loose ri ets, exchange it and test for a continued problem.

I see several on ebay right. ow. used ones and half of them have melted covers on that fuse! I did not see any melted connections in them though.

also of those reported as 69 or 70 fuse boxes many had different wiring on back or differed AMPS listed on front. same word but differed AMPS. more 10 AMP on left.
Are there really that many different 1970 style fuse boxes?

[svwilbur]

I am also afraid if I find my spare fuse boxes and they look ok that I may burn it up a d be out of luck with no more fuze boxes.

no one makes a reproduction one for a 1970?

[svwilbur]

1. What I would do is start by removing the fuse and connecting an multimeter with the red lead to the Amp side and the common lead to the Park side of the fuse. Set the multimeter to read DC on the 20V scale. YOU MEAN 20 AMP scale? Or did you mean to read volts. If so you cant read volts inline across the fuse, you must mean AMPS?

2. With both doors closed and the parking lights off it should read 0V. If not you have a short between the fuse and the head light switch or STG switch/buzzer/ door switch, or some other item. Again you mean 0 AMP?

3. After that I would set the multimeter to read Amps. (I thought it was alread reading AMPS? ) Turn on the parking lamps, if reading is greater then 20A immediately turn it off. (MY ability to read AMPS on my Meters is 10 AMP or less)
3a. Unplug dimmer switch. Recheck ammeter reading (short under the dash or at gauges)
3b. Unplug the dash to rear harness plug. Recheck (Short in the rear harness)
3c. Unplug headlight low/high beam relay. Recheck (Relay Bad)
otherwise short is in the front circuit.

4. At this point I would disconnect the battery and use a continuity testing function of the multimeter to check each item on the offending circuit until you find the problem. i.e. connect the common to ground and stick the other probe into each light socket and touch each contact. On contact should be ground and the other(s) and will sound the meter or should go power and if there is no short will not set off the meter. When you find the power wire that sets of the meter then you know the exact wire and general location of the short.

See the RED responses above and for the continuity I could do these tests #4 as it would not toast my multimeter.

[Solex68]

Usually the fuse box melting is caused by the rivet getting loose and corrosion between the "Bus Bar" and the little spring clip the holds the fuse.
If the fuses are just getting warm, you can usually peen the rivet. You need to take a fuse box off and support the other side with something very solid. I put a punch in a vise as an anvil.

I would follow Phil's advice.
It is the most likely cause in my opinion. I had this issue and I have seen other people with the same issue. The fix is easy. Remove the fuse box, clean it vinegar or electrical cleaner and then use a punch to tighten the rivet. Put it back together. Amazingly simple! No more heat.

[Linda]

CRC Electronic Cleaner found at OReilley's and Autozone is good.

Linda

[fj20spl311]

If you decide to tackle the crusty connections at the head lamp, they are a standard connector available at any good auto parts store.
If necessary, solder the new connectors in, cover the joint and wire with a little silicone and then shrink tubing to seal.

[svwilbur]

I looked in my inventory files on my computer. It said box 31 has fuse boxes. Of course I dig box 31 out and no fuse boxes. Lots of other good stuff, even stuff i just bought because I thought I did not have any!!!

I looked in 4 other likely boxes and no fuse boxes. Then I saw a cardboard box labeled "switches, fuse boxes and relays".... SCORE!

Looking at the pictures the top left has a similar problem one fuse up from mine, it melted through.
The upper right looks ok but is different on the back lower left area (where mine had the problem) it is missing some of the brass that the others have, a different setup I guess. It also has a couple of extra wires screwed into the back? May be ok. I am not sure what setup mine has.

The bottom two look best.
The one on the lower right looks ok too but some wires are coded differently with shrink wrap on them? ran out of proper coded wire that day at the plant?

One on left has a cover and looks ok but it has an area on back top right that someone tried to solder another wire to. Looks ok though right?


Which one looks best to you guys?

Also have a closeup pic of the solder on the one pole. looks like a little solder on the brass next to it too. That is OK right?

The small pics seem to be orientated properly but when you click on them they seem to flip one way or the other or upside down. My comments are for them in the correct mode as the previews so.

[fj20spl311]

Great to hear you have spares.
Just check to see if the fuses are getting hot with your fingers a few times.
If the rivets are tight, should be no problem.

[svwilbur]

Ok thanks. I think I will use that bottom one and ignore the part where someone had soldered another wire on. Maybe I will unsolder that nub that was left on the Blue wire with white stripe

[Jdflyer]

1. What I would do is start by removing the fuse and connecting an multimeter with the red lead to the Amp side and the common lead to the Park side of the fuse. Set the multimeter to read DC on the 20V scale. YOU MEAN 20 AMP scale? Or did you mean to read volts. If so you cant read volts inline across the fuse, you must mean AMPS?

2. With both doors closed and the parking lights off it should read 0V. If not you have a short between the fuse and the head light switch or STG switch/buzzer/ door switch, or some other item. Again you mean 0 AMP?

3. After that I would set the multimeter to read Amps. (I thought it was alread reading AMPS? ) Turn on the parking lamps, if reading is greater then 20A immediately turn it off. (MY ability to read AMPS on my Meters is 10 AMP or less)
3a. Unplug dimmer switch. Recheck ammeter reading (short under the dash or at gauges)
3b. Unplug the dash to rear harness plug. Recheck (Short in the rear harness)
3c. Unplug headlight low/high beam relay. Recheck (Relay Bad)
otherwise short is in the front circuit.

4. At this point I would disconnect the battery and use a continuity testing function of the multimeter to check each item on the offending circuit until you find the problem. i.e. connect the common to ground and stick the other probe into each light socket and touch each contact. On contact should be ground and the other(s) and will sound the meter or should go power and if there is no short will not set off the meter. When you find the power wire that sets of the meter then you know the exact wire and general location of the short.

See the RED responses above and for the continuity I could do these tests #4 as it would not toast my multimeter.

Hi Steve,
On point 1 and 2 I would set the multimeter to volts (it would also work set to amps). You are right that you can't read the voltage inline with the fuse, but you are checking if there is a short. You could also do the same thing by setting the multimeter to check continuity, attaching a lead to ground and then touching the parking side of the fuse with the other lead. (Many ways to skin the same cat)

If your meter can only read up to 10 Amps you would need to use a shunt and do a little math to get the Amp reading. Otherwise you would risk popping the fuse in your meter, or worse. If you would like to go this route and need some help, I'm sure someone here can help.

There are several different ways to chase a short and each has it's advantages.

With that said, after the fog of not being exhausted has faded (it was 2am where I was at when I started writing) I would have to side more with Phil. Otherwise that fuse should have popped. I would clean the contacts in the system as mentioned by others (good preventative maintenance) and ,personally, find out what the total load on your circuit is just to be safe.