So I picked up a 1970 Duster today, got some newb questions

-
S

Schneiderman

Well-Known Member
Joined
Mar 5, 2009
Messages
269
Reaction score
1
Location
Long Island, New York
Got it from the nephew of the original owner. Even got the original bill of sale, warranty and a bunch of service records. The car is in pretty good shape and drives real nice. It really doesn't need that much work overall, but there are a couple things I want to get squared away soon.

First of all the gas gauge and instrument panel lights don't work. Being a motorcyclist I am used to not having a gas gauge and using the odometer but it annoys me that the gauge doesn't work. Also I don't think the temp gauge works either but I didn't pay close attention, I only drove it about 10 miles home since picking it up. I looked at the fuses all look fine except the first 3 amp fuse (which I believe is the instrument panel fuse) looks suspect. I can't see a break but the wire looks bent and maybe burnt. Anyway, I'll go get some new fuses and replace that one and see what happens. If that doesn't fix the gas gauge and instrument lights, what do I do next?

100_1010.jpg
 
As far as the fuel gauge goes, I would look at the sending unit first inside of the tank. You don't have to pull the tank to get too it, but I would just to flush out the 40 years of gunk if the tank has never been replaced.
 
See if the dimmer function on the headlight switch is all the way off. Could be the headlight switch itself. Not uncommon for the pin in the back of the instrument cluster to be broken or oxidized. Light bulb burned out. Check the connection on the sender for the fuel. It needs a good ground. Check that you have good solid grounding from the block to the firewall etc...

John D. Beckerley
Austin, Texas
 
If both gas and temp gauge don't work, most likely it's the gauge voltage regulator. If it's not built into the gas gauge, then it will be a little rectangular can that's plugged into the back of the circuit board. Numerous places now offer solid state regulators (not the OEM points kind).
 
I guess another question I should have asked is what service manual should I get and where should I get it from?

How do I get to the sending unit? Do I go through the hole for the filler tube in the trunk? Once I get there, what am I looking for?

How do I get to the instrument panel bulbs to replace them (which screws need to be taken out)?

I will check the headlight switch, had an issue with that in my coronet, switch shorted out and the lowbeams wouldn't work.


Where is the circuit board with the voltage regulator? If the voltage regulator is built into the gas gauge, how do I check it and how do I replace it? Would I need a whole new gauge?

Sorry but all my experience is in working on bikes, not cars, and I've never had to troubleshoot an electrical problem.
 
Make sure the fuse is good first but it's common for the dash bulbs and/or holders to go bad also. Then try rotating the headlight switch knob back and forth (in the "on" position) as previously mentioned. Worst case scenario is that you'll have to pull the instrument cluster and do some testing. It's not as bad as it sounds....only takes 15 minutes or so once you've done one. 2 hours if you haven't! Pull the battery cable first!
On the gauges, with the ignition OFF, pull the wire off the sender and hook up a jumper wire from the wire terminal to a good ground. Turn the ignition switch to the ON position. If you see the needle move on the gauge, immediately turn it back off. Don't let the gauge peg to the end or it might burn out. If the guage works with the jumper hooked up, the sender is bad. If the gauge still doesn't work, the wiring, gauge, or circuit board is probably the problem. Sometimes it's just a loose or corroded connection but you'll need to pull the cluster to tell. If neither fuel or temp work, it could be the dash voltage limiter also as previously mentioned. It plugs into the dash circuit board on your model. If you need to pull the fuel sender, drain the tank down to a 1/4 or less (by driving or siphon) and disconnect the hose and carefully remove the ground strap. It should connect the metal hose nipple on the sender to the steel line that heads up to the fuel pump by spanning over the hose area. Use a cold chisel or big screw driver and tap the lock ring to the left 1/4 turn or so until it falls off. If you've drained the tank down, you can then just pull the sender out. If you didn't drain the tank, you've just taken a gasoline shower and can't see to get to the garden hose to wash your eyes out! Remember, no smoking, open flame, or so much as a hot girl friend near that open tank! You may luck out and find that it's just the brass float that developed a hole and sank. To test the sender, connect 12 volts to the sender terminal with a jumper, then connect your 12 volt test light inline from the battery ground on one end to the frame of the sender on the other. Move the float lever up and down and see if the light dims and brightens. No? the sender is bad. Cuts in and out? the contact arm may be worn or bent to where it doesn't make a good contact anymore. Sometimes you can rebend it carefully and make it work again. Take care that you don't snag the fine wires of the potentiometer or you'll for sure have to get a new sender. You'll have to bend the tangs on the metal can that holds the potentiometer and covers the contact arm so it can be accessed but it's easy to do if you're carefull. Leave the electrical wire or strap connected and just move it aside so you can work. Sometimes the contact arm will break off and be laying loose in the can. It can be soldiered back on with no problem but attach it exactly where was before or your gauge won't be accurate.
Have fun!
Mark
 
Hi. The sending unit should be over top of the diff before u take it out pull the power wire an ground it out ur gas gauge should move if not check ur reg under the dash it operates gas an temp gauge.if not that then pull ur sending unit check it with a ohm meter not sure what they should read check ur manual or some one eles will cime in with them.
 
Thanks cudamark and dartman. Hopefully I'll have time to at least start on this Sunday, but it will be a busy week so I don't know when I will be reporting back but anyway thanks for the help, it is very much appreciated (actually I'll probably have some more silly questions before I'm done).
 
You're at the right place to get any and all questions answered. Don't be embarassed of your lack of knowledge on these cars. We were all in kindergarten at one time ourselves. The bulbs are in little black sockets that have little nubs on either side. They twist in and out. The nubs break do to age. You may not have any bulbs in there. You can get replacement sockets from year one or go to the bone yard. They used them in 80's trucks. Hope I helped.
 
I replaced the fuse and nothing changed. I've confirmed that neither the temp gauge nor the gas gauge are working, and still no instrument lights. At this point I need some detailed instructions on removing the instrument cluster and checking back there. I starting trying it myself but I don't want to risk breaking anything.
 
Schneiderman said:
Got it from the nephew of the original owner. Even got the original bill of sale, warranty and a bunch of service records. The car is in pretty good shape and drives real nice. It really doesn't need that much work overall, but there are a couple things I want to get squared away soon.

First of all the gas gauge and instrument panel lights don't work. Being a motorcyclist I am used to not having a gas gauge and using the odometer but it annoys me that the gauge doesn't work. Also I don't think the temp gauge works either but I didn't pay close attention, I only drove it about 10 miles home since picking it up. I looked at the fuses all look fine except the first 3 amp fuse (which I believe is the instrument panel fuse) looks suspect. I can't see a break but the wire looks bent and maybe burnt. Anyway, I'll go get some new fuses and replace that one and see what happens. If that doesn't fix the gas gauge and instrument lights, what do I do next?

100_1010.jpg
Click to expand...

Had a 71 Scamp that had the same problem. It was a burnt trace in the instrument panel circuit board. It could also be the voltage limiter. If it's the limiter, contact me at [email protected]. I may have a spare. Mike
 
The voltage limiter or regulator is on the instrument panel circuit board mounted on the rear of the instrument panel. You will have to remove the panel. Disconnect the battery first. The ammeter guage connections are held on with nuts, I believe. Disconnect the speedo cable and bulk connector to the circuit board. The limiter is the small rectangular can. You can also check for burnt traces on the circuit board. The bulbs are in the black twist out bases. Mike
 
I was having the same problem on my Demon with the Fuel and Temp Gauges and I replaced the voltage limiter with the one from http://www.demonivr.com/index.html and it solved the problem with the gauges. The lights are another problem, could be as simple as a bad light switch, you will have to do some testing when the dash is out.
 
if that doesnt work the car is junk and you need to give it to me. :)

nice car.
 
You must log in or register to reply here.
-

Back
Top