New Owner! ‘75 620 issues

[Birddog223]

Proud new owner of a strong running 620 with a L20b. 89,000 original miles.

-gas gauge and temp gauge not working

- turn signals not working

Need some help on where to start please

[datzenmike]

 Does the oil light come on when you turn the ignition switch to ON. If YES then not the fuse. The Temperature and gas gauges are powered by a small voltage regulator set for around 7-8 volts. This prevents the gauges varying when the engine is off 12.65v, idling 13v or revved up to full 14.5 volts charging. The regulator is a set of points like in your distributor with a wire coiled around the arm which heats up and bends breaking the connection. It cools and bends back making the connection and repeats. The points can rarely become dirty and not make contact. Remove the gauge cluster from the dash and pull a folded strip if fine emery paper through them to clean and polish them. The voltage regulator in in the temperature gauge and powers the gas gauge also.

 

 

 

If the red oil pressure warning light works then the fuse powering the turn signals is OK. 

 

Check your 4 way emergency lights. If they flash then find the two flasher units under the dash on the side of the steering column above the pedals and swap them. If the flashers now work and the 4 ways stop working then the original turn signal unit needs replacing.

 

 

[klam07]

good luck!

 

Edited June 29, 2020 by klam07

[Birddog223]

No red oil pressure light. I’ll look through the fuses. In a Separate note, are there any fuse conversion To get away from the old round fuses? Maybe opening a can of worms but planning for future projects. Thanks for the knowledge. I’ll check the gauges shortly.

[datzenmike]

To check fuses, turn the signal on and hold a quarter across the fuses one at a time. When it starts flashing you've found it.

 

The 620 box is easy to remove and the wiring just unplugs. Take the fuses out (keep track) and wash vigorously with detergent and an old toothbrush, and rinse thoroughly. Now submerge overnight in a mixture of lemon juice and salt. In the morning use salt and a brush to polish, rinse and let dry.

 

[EDM620]

One thing to keep in the front of your mind: the majority of all electrical problems is the result of a bad ground. Check them before you get too far into diagnosing repairs!

[banzai510(hainz)]

Im late on this one

put new fuses in and recheck

 

my gas and temp gauge go out and I notice if I wiggle the fuses it comes back. There is a volt reg in back of the instrument panel bit it just a wrapped wire around a coil or some thing like that.unless it broke wire inside I don’t know how they go bad. I wiggle or put new fuses first

Edited July 4, 2020 by banzai510(hainz)

[Negative Ghostrider]

If all of your other external lights are working (brakes, corners, etc.) check your hazard switch. They are prone to failure and will prevent your turn signals from working. It could just be dirty contacts at the connections or it could be something internal. Pull the knob and see if the hazards work. If they don't you probably have a faulty hazard switch or bad connection. If they do, push it back in and try the turn signals again. If they still don't work try gently wiggling or twisting the knob to see if you get intermittent function. 

[homieelee]

On my '75 had the gas gauge & temp gauge not working.  You can go to your gas tank, and look on top of it, there should be 2 wires.  It connects to your fuel sending unit, unplug the one with the rubber grommet on it and ground it.  Check if you see the gauge needle moves, easier if someone in the cab to confirm.  For me, my actual fuel sender unit was busted as the needle moved but when connected back to the tank got nothing.

 

temp gauge for me never rose up.  I found out the PO completely gutted the thermostat, this made the coolant circulate 24/7 so the engine never warmed up.  Probably not your issue, but just throwing ideas out there.  

 

Majority of the time when i wrench on the datsun, it ends up being correcting PO's crap they did to it.

[datzenmike]

11 minutes ago, homieelee said:

 Majority of the time when i wrench on the datsun, it ends up being correcting PO's crap they did to it.

 

AMEN to that!!!

[Birddog223]

Thanks All! I finally got a day off. I’ll start with the fuses and grounds. Start small and go big, from what I’ve read. You guys are super helpful 

[Birddog223]

Anybody know how to remove these freggin knobs?!(wiper and lights)

[Birddog223]

Disregard.FYI the search button works in the site...

[Birddog223]

All lights working as well as gas gauge. Gutted the interior To have reupholstered. Any recommendations on getting the stock radio to work? Are they notorious to die? Tried to remove the dash but those fawkin screws under the front windshield...my God how are those supposed to come out? Next part is to stop the heater valve from leaking in the cab. 

[datzenmike]

It's 45 years old!!!  Leave it in place to fool thieves, buy a new player and mount under seat and use remote

[Birddog223]

No plans to take it out. Just thought it would be cool to work, especially the 8 track!! 

[Negative Ghostrider]

I'm leaving mine in the dash for theft deterrence. I am using a compact 4 channel marine-style amp under the dash and then just connecting my phone to it with a cable and using a Bluetooth controller on the steering wheel for volume/track/handsfree/etc. Pull the controller and stash the cable and nobody's the wiser. Putting generic parts express covers over the speakers to make them look cheap as well.