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'78 620 always blows wiper fuse


MattC280Z

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As the title says, my truck blows the wiper fuse as soon as the key is turned on, not starting, just on, I have unplugged the wiper motor, heater motor, and windshield washer motor. Still blows. Does anyone have any advice? I have ran a battery charger to the blower motor it works, the wiper motor didn't seem to work but the fuse should not blow because I have it unplugged. I replaced the fuse block so no issues there, and new fuses on the block.

 

It's been raining a lot where I live and I really would like to be able to drive in the rain lol. Is there a ground or plug that has a habit of shorting or going bad? Or a relay or fusible link, something? Am I on the right track?

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to me when you put key to On the Wire going to the the wiper motor ,fuse box is grounding out thus overloading the fuse and prevent the whole wire from melting.

Some where the wire is smashed to ground. or you ran a sheet metal screw soemwhere and maybe caught the wire. Anything done recently that you could have done soemthing.

 

 

get a meter and wire diagram and isolate the power wire and see if grounded. It has to be on the side if the key was in the ON position. if before the fuse would POP just by installing it. But this happen when Key ON

 

 

Just my opinion.

 

number of ways to ck this

pull + side of batt. then but a meter between the the starter lug where the main wire feeds the fuse box. then to ground. so when you put KEY to On the meter should read a short. then you halves in the wire harness and try this agin till it stops and you found what section your at

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Thanks guys I've only had the truck a couple of months and I haven't installed anything electrical since I've had it. The PO did install a radio but it's all ran from the Battery, when I get off work I will try and trace the wires. Thanks again I'll keep you guys updated

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I'll look when I get home but there may be more than one thing on the wiper circuit that you can check.

I can't recall but I'm pretty sure the fuse is for the heater motor, wiper motor, and washer motor.
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You need to find a wiring diagram for the truck.   Wiper motor wiring can get pretty confusing, because the wiper motor itself has to have a switch inside the motor, that keeps the motor running, until the wipers are in the parked position.  

You are on the right track, by unplugging the wiper, washer, and heater motors.   I would think the heaters motor, and wiper motor would be on different circuits, they are on a 521, but it is possible Nissan did combine them on your 620.

 

With the wiring diagram, you can figure out where the circuits branch off each other.  There may be one fuseable link that feeds everything, or there could be more fuseable links.

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You need to find a wiring diagram for the truck. Wiper motor wiring can get pretty confusing, because the wiper motor itself has to have a switch inside the motor, that keeps the motor running, until the wipers are in the parked position.

You are on the right track, by unplugging the wiper, washer, and heater motors. I would think the heaters motor, and wiper motor would be on different circuits, they are on a 521, but it is possible Nissan did combine them on your 620.

 

With the wiring diagram, you can figure out where the circuits branch off each other. There may be one fuseable link that feeds everything, or there could be more fuseable links.

Good point man I've got the FSM at home I'll take a look at it when I get off work. Thanks

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If multiple power to other stuff then disconnect them to isolate the proplem. Heater , wiper eft.....

It blows as soon as the key is turned. I've tried it with one part unplugged and with all f them unplugged. Same result, I did delete the AC from the interior. It was already stripped from the engine bay. But it appeared to be all independent from the other components, is this correct?
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First of all this should be a 15 amp fuse so it you are using something less this may be the problem.

 

 

The fuse that powers the wiper motor also powers...

 

The tachometer if you have one.

The heater fan motor

The washer pump.

 

Thanks guys I've only had the truck a couple of months and I haven't installed anything electrical since I've had it. The PO did install a radio but it's all ran from the Battery, when I get off work I will try and trace the wires. Thanks again I'll keep you guys updated

 

This, right here. POs are idiots.

 

Radios need constant power to keep the clock and memory function working and they need a switched supply so it turns off with the key and not kill the battery. Then there are the lights that should be wire into the illumination circuit so they come on with the light switch. I'll bet he's tied something to that fuse or pinched something cramming the radio in there. There's no other reason for what you describe other than the PO.

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First of all this should be a 15 amp fuse so it you are using something less this may be the problem.

 

 

The fuse that powers the wiper motor also powers...

 

The tachometer if you have one.

The heater fan motor

The washer pump.

 

 

This, right here. POs are idiots.

 

Radios need constant power to keep the clock and memory function working and they need a switched supply so it turns off with the key and not kill the battery. Then there are the lights that should be wire into the illumination circuit so they come on with the light switch. I'll bet he's tied something to that fuse or pinched something cramming the radio in there. There's no other reason for what you describe other than the PO.

I never really considered the radio but I could look into it. I used all my 15A fuses yesterday so I put a 20A in and it burns it just as quick. Tomorrow I will check where the Radio is connected. However once the fuse blows the radio isn't affected nor changed.

 

Completely off topic but my seatbelt light and buzzer doesn't work now when the key is turned. Just started today don't know if it's connected.

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Take the radio out and see. It's unlikely Nissan did this, they're pretty careful. What happens is owners. Owners do things to Datsuns like shoving a radio in there that wasn't made for it. They use screws and the twist wires together to make it fit and work, and along the way they foul something up.

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Okay last night I had a friend come over (electrical tech at Toyota) and we pulled the dash, and the harness, and checked every junction that comes from the wiper wire, found two wires along the harness that were touching, I think we solved it.

 

then check the radio, will post pics later of the hodge lodge job this guy did. With the radio unplugged the fuse does not blow. :)

However were going to wire the radio in the right way before we reinstall,

 

I deeply appreciate all the feedback guys, you guys really pointed me in the right direction I am by no means an electrical man but I learned a lot last night. :)

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I kept having similar problems on my 79 kc and what I did is got the wiring diagram and went to kinkos and for about 20.00 they blew them up to 36x48 and you wouldn't beleive how clear it looks and easy to see. I started there and went through everything.ended up switching out switches etc.

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-UPDATE-

 

Unplugged everything from the dash then turned the key on plugging in all the plugs and the switch to blower motor is what caused the fuse to blow. However, now I have another issue.

 

Now the buzzer and timer relay aren't working. I've taken them off and ran power to them they work with power. Then I used my new multimeter to test power at the plugs to them, they work when the key is on. However why doesn't the buzzer buzz if I have power at the plug and the relays work?

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