Elect tricky stuff

Quick google found that most vehicles have 6volt instruments. The difference in this case is that previously you only had 6volts. So you don't have a CV unit like my AB has.

The regular fix appears to be to fit a small solid state 12-6v converter for the instruments. The same problem is probably occurring for the temp also. Just you may not have run long enough.

Out of curiosity temp wire the 6v battery to the fuel gauge and sender and check it is still working before you go any further.

Think you will find that in this case a simple voltage divider using a resister isn't going to be good enough from what I can see. Try checking jaycar electronics they would probably have a little converter. Note it won't be big enough to do much more than the instruments.

No voltage stabiliser as far as I can see, unless it is built in to the gauge. Other instruments ie temp and oil pressure are mechanical and working fine.
Been reading up on Google, I think the fuel gauge reads current rather than voltage. Will try it back on 6 volts and then a lower value resistor.

The point i was making before atki was your truck might have 6v gauges but wouldn't have a voltage stabiliser or CV unit. But I think you will need one now!

Wouldn't keep trying resistor's at random you might let out the magic smoke!

Hi Pete, you may have sorted yours out by now. I've recently bought a Mainline ute that has been rewired and converted from 6 to 12 volts. The guages wern't working when I got it, anyway, I found a blown fuse and away they went, only thing being they were far from acurate, first drive after that the temp gauge is right up near hot, I pulled up and the motor didn't seem overly hot. I decided to put in a set of gauges under the dash just so I know for sure, I put in some Murphy gages which I havn't got around to hooking up to a buzzer yet, but when I was fiddling around under there I found this weird home made arrangment of what looks like resistors that are in the wiring to the gauges, obviously to reduce the voltage. Then I started to trace a bit more of the wiring, lo and behold, bugger all of it is fused, so I put another fuse block in ran the wiring out of the ignition switch through some fuses. Upshot of all this though, was I had to figure out what to do with the gauges and heater fan running on 6 volts and the rest of the car running on 12 volts. I've ordered a Redarc 12v to 6 volt reducer off Ashdowns, I think it was about $150 and I'm going to wire that in off the ignition circuit then to another small fuse block so that all the 6 volt things run off that. I also rang a mob that specializes in fixing car instruments, old mate said the gauges might need recalibrating after having 12 volts through them, and they had a unit there for reducing the voltage, but that still wouldn't have fixed the heater fan problem. So I'm going to put in the Redarc unit and see what happens. Just out of interest the 4' murphy temperature gage was amazingly cheap, about $115, but I bought a 6' one with a lighting kit for another little job and it was $200, they are pretty cheap insurance I reckon, you can set what temperature you want the alarm to go off at, so I usually set it just above as hot as the engine runs at and carry the allan key to adjust it around for a little while if it needs a bit more adjusting.

Out of interest, 6V is easy to achieve for small currents such as a gauge this link:
www.circuitstoday.com/6-volt-regulator-circuit-using-7806

Uses the 7806 which is 1 amp at 6 volts out. Your main batteyr would be where it says C1 on that diagram. Note that is exactly 6 volts, you can put a small diode in between ground and pin 2, which would lift it to 6.6 volts which may be more appropriate for a car 6V system.
There are larger voltage regulator chips and also the keen can add transistors to increase the current capacity. It can be done by anyone into electronics with due care for earthing and a little spike suppression maybe added.

Just found a simpler site:
sites.google.com/site/cx500gl500/7volt

The LED is the little light you see on most electronic equipment and they are actually a diode which he uses to up the voltage of the 7805 (5V regulator) to closer to the nominal vehicle 6 volts which is more like 7 when running. As he states the particular model does 2 Amps which is nicer.

Thanks Trackhappy, there was 3 of those 78S05 or something that looks pretty similar soldered onto a bit of copper with some heat sinks on it, one for each gauge I'd guess. Still got to drive the heater fan anyway, so I'll stick with a voltage reducer, but it looks like a cheap and effective way around the problem.

BigC,

The Heater fan is one of the easiest things to convert.

With Atkipete's wiper motor he sent me the amps that he wiper motor consumed at 6V. I then calculated the resistance of the motor. Then used this to calculate the size of the resistor required to achieve 6V across the wiper motor. Important thing to consider is that I also calculated the amount of amps consumed by both the resistor and the motor when running on 12V.

The issue is of course that the wiper motor amps will change depending on if the screen is wet, dry or snow! So may not be perfect under all situations. But should be adequate for the Dodges uses.

The heater fan is predictable and constant load! So just a simple resistor in series should be adequate.

In the case of Atki's wiper it worked out a 1.9ohm ballast resistor should be adequate to do the wiper!

I would suggest using a electric step down for the guages if you want them accurate. I suggested www.jaycar.com.au/productView.asp?ID=AA0218 to Atki for his guages (only one ran on power rest mechanical!)

Last I heard from Atki (has been on a bit of holidays). The dodge is all up and running again on 12Volts. Hopefully when he gets back he will let us know what he did!

But you are correct to have plenty of fuses. I know my AB has very few fuses. Which has caused some interesting issues over the years! The ACCO has circuit breakers on the main high current circuits (mainly lights etc) and the good old glass tube fuses for the ignition and accessories lines. Don't know if it is the original fuse set up. But is about the best setup I can think of.