Advice on fj40 wording. (1 Viewer)

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I have a 1970 fj40. It looks like the PO put a aftermarket wiring system in.its definitely not stock. I am having a problem with the head lights some times the passenger headlight does not work or sometimes it is very damn. And he same goes for the turn signal .then there will be times it works just fine. Could this be caused be the fuse block getting wet? Or is this the result of a bad ground? If it's a ground were should I look. I am the worst when it comes to this type of trouble shooting and any help would be really appreciated. You will not insult me by over simplifying .thanks
 

Coolerman

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The best advice I can give you is to find a friend that understands automotive electrical systems and buy him his favorite beverage in exchange for his help.

Saying that, it does sound like a ground issue. All the lights on that year FJ40 ground through their mounting points. Make sure all the housings are properly grounded to bare metal.
 

DSRTRDR

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for the turn signal: check the rod that goes from to the turn signal switch down on the steering column to the turn signal level by the steering wheel - make sure the contact is clean in the brass rod socket and on the rod itself - you may have to loosen the switch down at the steering column and align it both in height and parallel to the column to get the best contact.

give a shout if you happen to come to Baton Rouge with the truck . . .
 
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The best advice I can give you is to find a friend that understands automotive electrical systems and buy him his favorite beverage in exchange for his help.


Saying that, it does sound like a ground issue. All the lights on that year FJ40 ground through their mounting points. Make sure all the housings are properly grounded to bare metal.

Thank you I really did not know were to start.
 

roadstr6

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I had the same issues on my '70 and it turned out that they were not related. Turn signal switch would only work on one side. The actuator rod was just so worn that it could not fully move the switch a the way from right to left. I had to get a whole new switch. My headlights were dim and the fuse would get real hot...so hot it melted the solder out from under the caps (but it never blew!). I traced this problem to the back side of the fuse panel where the rivets had gotten corroded and caused a short. I ended up getting a new fuse box. If you end up needing one, they are hard to find but I have a source. PM me and I will hook you up.


...via IH8MUD app
 

Coolerman

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When you get a fuse in a fuse block that gets hot, but does not blow, it can make you think the fuse is not working or the laws of electricity have suddenly changed. In reality, the situation you described above is quite common on old vehicles, ie the fuse block contacts melting but the fuse not blowing. So how does that happen? What's going on is this. The clips that hold the fuse in place develop corrosion on them. (Or it could be corrosion on a switch contact, or a connector contact) Corrosion acts like a low value resistor placed in line between that end of the fuse and the clip. What you have is a circuit that consists of the battery, the resistor (ie the corrosion), and the fuse, then the load, say the headlights. When you turn on the head lights, the current flows through all parts of the circuit including this low value resistor. Resistance in a circuit produces HEAT! The heat that develops at that end of the fuse is what melts the fuse block housing.

So why doesn't the fuse blow with all that heat? The math will show why! In a normal working circuit the headlights would pull say 6 amps total. Ohms law states that to find the resistance in a circuit you use this formula R=E/I Where R= the total resistance, E = the voltage (we will use 13.2 volts) and I = the current. Plugging in the knowns we get R= 13.2/6 so total circuit resistance (ignoring wire and switch contact loses) is R=2.2 Ohms. The headlights are in parallel so each headlight has about 1.1 ohms of resistance and draws about 3 amps.

Ever put your hand on a headlight that has been on for awhile? It gets hot! Now lets introduce the corrosion, ie the resistor at one end of the fuse. This resistor is in series with the headlights. Lets assume it's one ohm resistance. To determine current flow now and WHERE the current is flowing, we have to recalculate. We know from above that each headlight has 1.1 ohms resistance in a normal circuit. Adding the 1 ohm of corrosion resistance to the 2.2 ohms, we get a total circuit resistance of 3.2 Ohms. Recalculating for current using I=E/R gives us 13.2/3.2 = 4.125 amps of total current flow. Notice now the circuit is flowing less total current? Whats happens to the headlights? They get dimmer! What happened to the other 1.875 amps of current? It's being dissipated by the corrosion on the fuse clips as pure heat! The fuse is only seeing 4.125 amps, so it doesn't blow, even though the clip holding it is melting the fuse block!

Keep this concept of resistance in a circuit causing heat and you can use it trouble shoot dim lights. If you own one of those "Laser Guided Infrared Thermometers" you can track down loose and corroded connections by looking for heat at connectors, switches and fuse blocks.
 
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That
When you get a fuse in a fuse block that gets hot, but does not blow, it can make you think the fuse is not working or the laws of electricity have suddenly changed. In reality, the situation you described above is quite common on old vehicles, ie the fuse block contacts melting but the fuse not blowing. So how does that happen? What's going on is this. The clips that hold the fuse in place develop corrosion on them. (Or it could be corrosion on a switch contact, or a connector contact) Corrosion acts like a low value resistor placed in line between that end of the fuse and the clip. What you have is a circuit that consists of the battery, the resistor (ie the corrosion), and the fuse, then the load, say the headlights. When you turn on the head lights, the current flows through all parts of the circuit including this low value resistor. Resistance in a circuit produces HEAT! The heat that develops at that end of the fuse is what melts the fuse block housing.

So why doesn't the fuse blow with all that heat? The math will show why! In a normal working circuit the headlights would pull say 6 amps total. Ohms law states that to find the resistance in a circuit you use this formula R=E/I Where R= the total resistance, E = the voltage (we will use 13.2 volts) and I = the current. Plugging in the knowns we get R= 13.2/6 so total circuit resistance (ignoring wire and switch contact loses) is R=2.2 Ohms. The headlights are in parallel so each headlight has about 1.1 ohms of resistance and draws about 3 amps.

Ever put your hand on a headlight that has been on for awhile? It gets hot! Now lets introduce the corrosion, ie the resistor at one end of the fuse. This resistor is in series with the headlights. Lets assume it's one ohm resistance. To determine current flow now and WHERE the current is flowing, we have to recalculate. We know from above that each headlight has 1.1 ohms resistance in a normal circuit. Adding the 1 ohm of corrosion resistance to the 2.2 ohms, we get a total circuit resistance of 3.2 Ohms. Recalculating for current using I=E/R gives us 13.2/3.2 = 4.125 amps of total current flow. Notice now the circuit is flowing less total current? Whats happens to the headlights? They get dimmer! What happened to the other 1.875 amps of current? It's being dissipated by the corrosion on the fuse clips as pure heat! The fuse is only seeing 4.125 amps, so it doesn't blow, even though the clip holding it is melting the fuse block!

Keep this concept of resistance in a circuit causing heat and you can use it trouble shoot dim lights. If you own one of those "Laser Guided Infrared Thermometers" you can track down loose and corroded connections by looking for heat at connectors, switches and fuse blocks.

That helps .it looks like I have a painless wiring kit in my j40.thank goodness I have not had anything melting . thanks coolerman
 

DSRTRDR

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the Painless fuse block wouldn't have those contact problems - with a Painless harness (or any ez-wiring or somesuch system), the most likely problems are mismatch between wiring/ground and Toyota switches

the Painless and Toyota wiring philosophies do not agree at some of the switches, but the mismatches can be overcome if you reconstruct the OEM wiring for the brake/blinker/hazard circuits according to the Toyota wiring diagram
 
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the Painless fuse block wouldn't have those contact problems - with a Painless harness (or any ez-wiring or somesuch system), the most likely problems are mismatch between wiring/ground and Toyota switches

the Painless and Toyota wiring philosophies do not agree at some of the switches, but the mismatches can be overcome if you reconstruct the OEM wiring for the brake/blinker/hazard circuits according to the Toyota wiring diagram
Thanks Claudia
 

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