Datsun Roadster Forum-311s.org

I have a '68 with a '68 instrument cluster and a bit of a mash-up for the rest of the dash. The gas and temp gauges stopped working on the last trip and it sounds like the voltage regulator (VR) is on the fritz. My third VR on its way ... the first one died ... the second one is now on the fritz. With the remote diagnostic help of Ross and a mechanic I've cleaned it up, but it still is non-functional (NF).
Is there a test of some sort I can do on the leads coming from the fuel tank & temperature sensor to make sure the right amount of power is coming through? Any suggestions to help?
(longer term the plan is to replace the entire wiring system, but until then I'd like to have at least my temperature gauge back....not a big deal to run out of gas ... I hear it's not that good for an engine to get it too hot )

Why not fix the ones you have now for about $6 each?

http://www.311s.org/pmwiki-311/pmwiki.p ... VoltRegFix

Low amp circuits like the guages are problematic on connections , as you need great conductivity .
The copper wire oxydating and brass spade connector doing the same are a lot of it . It's best to solder those solid on old cars ...Kia had a update to do this on theirs.
Also cars that have big dogs panting do cause many electrical circuit open circuits the acidic saliva tarnishes the Conn. You can see the saliva coating the inside windows usually
I once at Mitsubishi , talking to a customer complaining this car had many electrical problems , I told him it's likely your dog , see the coating of saiiva on the inside of the glass he answered we haven't got a Dog that rides in the car ! I said cars with teens young adult parking do it to ....he rubbed the inside glass saw the coating & kind of quit arguing about it...
There was a hot ? 16-18 yr old girl at the vending machines ,we had noticed, this was her car , Dad seemed irate as they left

devo wrote: ↑Wed Oct 13, 2021 7:37 pm Why not fix the ones you have now for about $6 each?

Thanks for the link & suggestion ... I am hoping to test the circuit so I don't keep blowing the VR ... whether I have an upgraded/fixed one, or original.

RP

The upgraded, electronic VR is in. Gas Gauge goes to max full (have about 3/4 to 1/2 tank now), and thermometer goes to full hot when at running temperature (Laser sensor shows about 121F).
I will check on connections, but apart from that, any suggestions?

Ralph wrote: ↑Wed Oct 20, 2021 11:46 pm The upgraded, electronic VR is in. Gas Gauge goes to max full (have about 3/4 to 1/2 tank now), and thermometer goes to full hot when at running temperature (Laser sensor shows about 121F).
I will check on connections, but apart from that, any suggestions?

How old is the VR the solid state ones can. go bad over time , sounds like it is getting to many amps ,( if it is dropping the volts , I would hook up a tiny bulb and see what it does, you could try a variable resister inline past the VR to further adjust it your temp sender in the engine ,have you checked sender settings / readings on it with a multi meter cold &hot
Also if you have the new MFI alternator 3 phase / square wave alt that like lt will change the settings
Does it go up quick ?

Red:
Thanks for the help.
Electronic VR is brand new.
I haven't checked the sending unit settings or readings for either gas or temp gauges. I'd need to be pointed in the right direction on how to do that and what the readings should be. Any links to instructions would be appreciated.
Tools I have now are a multi-meter, and a couple testing lights.
RP

Better tell your wife that you have to go straight home!

If your gas and temp gauges are reading high, you should check the voltage coming out of your new instrument voltage regulator . It sounds too high or maybe not hooked up right. Is it adjustable?

Red:
Missed this-
“Does it go up quick ?”
Gas gauge flicks up and down slightly a few times then runs up to over-full. Pace of the rise is a bit quicker than a normal reading would go.

Yeah Ive had ones do it
If you disconnect the sendor wire at the tank does it go to empty? If not its grounding thru something
Stock alt ? If not mistaken theres a small coil that pull s opposite the coil inside tthathe main one makes it go up to stablize it that may be on the brink my temp guage on an eclipse does it until I slap the sh!t out of the dash
...ya got to show it whos boss

Alternator is non-stock ... GM equivalent (I think?) one-wire
I'll try the fuel sender disconnect and report back...hopefully later tonight
RP

steve_car wrote: ↑Tue Oct 26, 2021 10:31 am If your gas and temp gauges are reading high, you should check the voltage coming out of your new instrument voltage regulator . It sounds too high or maybe not hooked up right. Is it adjustable?

Pretty sure the new VR is not adjustable, but I'll check with the vendor plus hook it up to my multimeter.

Ralph wrote: ↑Tue Oct 26, 2021 8:15 pm Alternator is non-stock ... GM equivalent (I think?) one-wire
I'll try the fuel sender disconnect and report back...hopefully later tonight
RP

Yeah those can do it puts out way more volts and amps at idle , to run the fuel pump & ecu .
Is the VR on the neg side of the circuit , try that

I had my temp and gas gage going up and down and found there is a regulator on the steering shaft under dash that had to be replaced and the gages worked perfect again. PS the gages worked until the engine warmed up then temp would go to zero as well as gas gage