replacing a fuel gauge unit

[Thundercloud]

Ok so I have a 79 Winnebago double tanker and my old gauge circut board fried so none of my gauges are currently working accept my vacumm gauge which is mechanical. Anyway my question is can I put a seperate fuel guage in with its own voltage limiter and if I switch tanks then would I have two fuel gauges? Because I want to make my oil pressure, water temp, tranny temp all. mechanical and throw the old gauge panel in the trash. Any helpful insight would be ausome on how the older fuel gauges work.Thanks!

[LJ-TJ]

   
• Have you got a picture of your instrument panel. Here's a thread of the changes I made to mine. There are a lot of gauges out there. I went with autometer as I felt they were the best and made in the USA. If you keep and eye on Craigs list you can pick them up very reasonable.

http://www.classicwinnebagos.com/forum/index.php/topic,7201.msg43690.html#msg43690

[Thundercloud]

I'm having trouble uploading pics from my phone right now but my question is I guess if I'm going to put a  aftermarket fuel gauge in how would I go about doing that?

  Hm?

[legomybago]

You need to find out what your fuel level sending units ohm range is..

They have:
0-50ohm gauges and sending units
0-99 ohm gauges and sending units



You could even have a fuel level sending unit installed backwards/upside down??? One of my old rv's had a 0-99 ohm gauge in the dash, with a 0-50 ohm sendor installed upside down and backwards on the tank pickup assembly!! The more fuel you had, the emptier the gauge read!! I was able to flip the sending unit around etc...but with a full tank of fuel the gauge will only read 1/2 tank!! hahaha 

[DaveVA78Chieftain]

Sorry but if you are wanting to use the existing sender then 70's to early 80's Dodge fuel gauge ohm value is
10 to 73.

Dave

[Thundercloud]

Ok yeah on those its a voltage limiter. I  thought it would be cool to have a bigger fancy gas gauge on it to match my big fancy fuel. Lol

[UK-Winnie]

I've played with this a bit on muscle cars - as Dave says the '60s '70s gauges don't match with later senders (and vice versa).  To make it even worse the early gauges work off a tiny heating element inside the gauge and the resistance value of the gauge actually changes as the element heats up, so it's not even a linear relationship between them. 

You can in theory make a modern sender work (sort of) with an older gauge by dumping the limiter and adding resistors into the circuit (one in parallel across the gauge and one in series with the sender) but I've never tried it.  No doubt there is a way to make a newer gauge work with an older sender but I think it would be really tricksy.

I have read that this all stems back from the even earlier systems where everything was 6 volt.  Apparently when the rest of the system moved over to 12 volts the manufacturers stayed with 6 volt gauges and senders to save re-development costs and instead they just added the voltage limiter.  Later in the '80s they finally got round to introducing some 12 volt gauges and senders.

I have upgraded the older systems using a semiconductor voltage regulator like these:

en.wikipedia.org/wiki/78xx

The original voltage limiters are supposed to be 5 volt, but I found the 5 volt semiconductor regulators (part # 7805) did not move the gauges enough whereas the 6 volt regulators (7806) work very well, so that ties in with the legacy 6 volt theory and I suspect the original voltage limiters (which are actually an intermittent 12 volt signal) approximate closer to 6 volts than to 5 (if they are working properly).

Probably none of that is helpful in this case, but I think it's interesting (insert anorak smiley)

[DaveVA78Chieftain]

How to upgrade the Dodge instrument panel Voltage Regulator: http://www.allpar.com/history/mopar/electrical2.html

Replacement 74 & later Dodge Motorhome instrument panel circuit board: http://www.ebay.com/itm/like/120869044850?lpid=82

Dave

[UK-Winnie]

How to upgrade the Dodge instrument panel Voltage Regulator: http://www.allpar.com/history/mopar/electrical2.html
Dave

Yeah that one - it works on Fords just the same, I don't know about GM ?

[DaveVA78Chieftain]

I don't know about GM

Not a clue

[legomybago]

Good read-ups Dave

I've been thrown for a loop on Gm fuel gauges....My experience: Fuel gauge was not accurate, so I checked sending unit=good, wiring=good, gauge??=seemed to be good with sweeping needle?, I was at a loss?, so I ordered a factory 1986 P30 gauge off of ebay for 20 bucks or something anyway W% , when it came in the mail, it had a little RESISTOR block that bolts to the backside of the gauge to decrease the resistance if I remember right. Turns out my resistor block was bad N:( ? I just switched out the blocks and BAM! Now I have a good fairly accurate gauge.

And GM fuel sending unit system is opposite/backwards from Ford and Dodge...That through me for a loop at first too...I've never owned GM rigs before

[Thundercloud]

Its too bad that they couldn't of made mechanical fuel gauges apart from shoving a hose in blowing with your mouth and listening to how strong the bubbles sound. Lol

[legomybago]

We could have sight windows

[Stripe]

OOh, OOh, How's about one of these???



Talk about "Old School".... 

[JDxeper]

I upgraded my dash regulator, even an easy fix for me.  I got the biggest bang for the buck when I replaced the headlight switch.  Even the idiot lights worked.  Now don't ask me why?   Gas gauge still only goes to 3/4 on either tank.  All the rest, temp, oil, volt work.  Oh, 78 Winnebago with a 440.