‘77 280z signal fuse keeps blowing up

[dutchzcarguy]

15 hours ago, 240zadmire said:

the fuel gauge and A/C fuses start warming up. 

Whay the fuelgauge has to do with high current escapes me.. but..

What i have seen in fuse boxes is that there are rivets in the copper strips on the underside and they sometimes get a bit loose and create a resistance that heats up the connection, every time a bit more untill things start to catch fire!

SO CHECK THE FUSEBOX CONNECTIONS PARTICULARLY THE RIVETTED COPPER STRIPS !!  👍

[dutchzcarguy]

16 hours ago, 240zadmire said:

Check all the fuses by hand touch and they are as cool as cucumbers

Today you can buy a infrared thermometer for a few bucks.. saves you a lot of guesssing..

[240zadmire]

I didn’t carry the infrared thermometer with me at the time 😞 

highly possible the culprit is at the connector under the blower toward the transmission tower.  It corroded and have some greenish color to the pins.  2 of the pins too corroded I had to pull off and bypass.

 

the infrared dot is hard to see in the photos.  One of the fusible link is quite hot too.

 

 

Edited August 12, 2022 by 240zadmire

[Zed Head]

The dot is only for aiming.  The measured area might be much broader.  The farther the device is from the area, the broader the area is that is measured.  Probably best to hold the pyrometer straight and scan over the fuses if you want to find a hot one.  And the closer the better for a small area.

There is a bunch out there about all of the various details, some it way in to the weeds.  Here's one reference.  They're not really designed for small area measurements.  I have one that has a socket for a thermocouple.  That's what you'd really want for measuring fuses and other small areas.

https://www.williamsonir.com/blog/3-tips-proper-pyrometer-maintenance/

" For single-wavelength sensors, alignment is critical as the pyrometer takes an average temperature of whatever it sees in its field of view.  Therefore a single-wavelength pyrometer needs a full field of view of the target to make an accurate measurement, so as not to average in other non-target temperatures. "

[240zadmire]

The hottest one is 100% on the AC fuse following the fuel gauge.  It quite hot to the touch.  Another warm location is at the connector at blower. I might have to cut those wires and create a 6 spades/blades in place.  

[Zed Head]

What about the flasher fuse?  That's the one that is blowing, right?

[240zadmire]

That’s the weird one.  I ran the A/C for good 15 minutes, switching the blower level around and playing with the flasher left/right… no fuse blown.  Not hot either.  Only the AC and the fuel gauge are hottest.  The AC clutch disengaged intermittently when I switch to max blower.

 

it’s toying with me 🙂 

Edited August 12, 2022 by 240zadmire

[Jeff Berk]

I don't understand what the AC has to do with the turn signal fuse. 

Just wondering, is this an original Nissan AC or did someone install an aftermarket one at a later date, possibly with wiring something related to the AC to the turn signal circuit?

 

[240zadmire]

The AC is original except the drier replaced a year ago… 

by coincident while troubleshoot the flasher fuse blown, I touched all the fuses and notice AC and fuel gauge fuse sockets were the hottest.  I don’t think that normal to be that hot to the touch.  The AC and fuel gauge fuse sockets hot if AC is running.  Fuel gauge fuse cool otherwise.

my electrical knowledge is rudimental at best… I’m doing trial and error to narrow down the issue.  So far signal fuse hasn’t blown, yet.  

Edited August 12, 2022 by 240zadmire

[Zed Head]

The diagram suggests that the short that blows your flasher fuse would be in the Hazard switch, or the flasher unit itself, or the wires between the fuse and the flasher unit.  The flasher unit provides resistance to stop a short to ground after it from blowing the fuse, I think.

Edit - but it would have to be a constant short circuit that doesn't pull enough to blow the fuse by itself.  Using the signal switch pushes it over the edge.  Since the signal switch completes the circuit to ground.  The voltage is always in the wires.

Edited August 12, 2022 by Zed Head

[Captain Obvious]

Really hard to troubleshoot intermittent electrical issues, especially from a distance, but here are my thoughts...

First, I suspect the only reason the "fuel gauge" fuse is heating up is because of simple convection and conduction. My theory, which is mine, is that the heat from the A/C fuse is rising and heating up the fuel gauge fuse. And the second part of that theory is that there is really nothing wrong with the fuel gauge fuse system and the apparent heating of the fuel gauge fuse is a simple distraction.

And as for why the A/C fuse is heating up so much... Does that fuse and fusible link heat up that much when you run the fan at it's highest speed WITHOUT the A/C being on? In other words, have you checked the temp of that fuse running the fan on HI while the HVAC system is in HEAT mode? It could be as simple as a tired old blower motor with dried out creaky bearings that doesn't want to spin fast anymore.

Next, I'm having a hard time coming up with a link between your turn signal fuse popping and the A/C system. You have described a situation where you have the A/C on, and when you turn the signal on, the fuse blows. Have you ever had the situation where the turn signal is on and working correctly and then when you turn the A/C on, the fuse blows?

And about the compressor kicking off when the fan is on the highest speed, we can talk about that later. It's probably dirty contacts inside the fan switch.

 

[240zadmire]

3 hours ago, Captain Obvious said:

Really hard to troubleshoot intermittent electrical issues, especially from a distance, but here are my thoughts...

 

Just because it's right in front of my face doesn't mean it's easier for me.  😉

Just want everyone to know that I appreciate all the input.

I'm not sure why the fuse gauge is heating up.  Doesn't look like the back plate share the same pins.  I don't think anything is wrong with it either.  Both AC and fuel gauge are still functioning.  I'm more concern about the AC is so hot to the touch.

I did turn on heater full blast.  The AC's fuse does warm up but hot as much.  I didn't get the chance to measure the fusible link temperature.  Got distracted 😞

 

will try more later tomorrow.

Stay tuned.