SUNRADER LANDON Posted August 11, 2016 Report Share Posted August 11, 2016 Looking for a fix for the fuel gauge. I pulled apart my cluster, cleaned up some connections, and upon reinstall, I noticed the needle moved slightly, whereas before it wasn't moving at all. I checked the connections with voltmeter. I believe I was only reading .5 v. Also checked all my fuses. All good. Anyone have similar issues/ potential fix? 1 Quote Link to comment
Lockleaf Posted August 11, 2016 Report Share Posted August 11, 2016 Does your coolant temp gauge work? 1 Quote Link to comment
flatcat19 Posted August 11, 2016 Report Share Posted August 11, 2016 Voltage regulator on back of cluster. Bad connection at fuel level sending unit. Bad fuel sending unit. Empty tank. 1 Quote Link to comment
SUNRADER LANDON Posted August 11, 2016 Author Report Share Posted August 11, 2016 Flatimus, Thanks for the response! I did run out of gas the other day...so there's that. I'm guessing the sending unit is in the tank? The connection would be at the top of the tank? In other words I'd have to drop my tank? Also pulled the cluster to look at the gauge (had no clue what I was looking at) what does the volt reg look like and how would I go about fixing it? Thanks again 1 Quote Link to comment
SUNRADER LANDON Posted August 11, 2016 Author Report Share Posted August 11, 2016 Yeah accidentally posted twice. My bad. The temp gauge is responsive, though I don't know how accurate 1 Quote Link to comment
flatcat19 Posted August 11, 2016 Report Share Posted August 11, 2016 I don't know much about 720s so my knowledge to help will be pretty general. Find a factory service manual online. So invaluable in helping you diag the components and give proper values when testing. On my 521, I have a pop out panel in the bed that opens to the fuel level sending unit. But yes, it is on top of the gas tank. 1 Quote Link to comment
SUNRADER LANDON Posted August 11, 2016 Author Report Share Posted August 11, 2016 I've got the Haynes 720 manual, it's been a great tool. My 720 is a motorhome, so dropping the tank is a probably unavoidable 1 Quote Link to comment
flatcat19 Posted August 11, 2016 Report Share Posted August 11, 2016 The Haynes manual is weak. Finding a Nissan FSM is the best bet. And you should be able to find it free. 1 Quote Link to comment
datzenmike Posted August 11, 2016 Report Share Posted August 11, 2016 I have the '84 FSM and will look that up when I get home. The tank sender resistance varies from 10 ohm (full) to 80 ohm (empty). The gauge cluster has a voltage regulator that provides a constant 8 volts so the gauge does not change when running at 14.5 volts and with the key off at 12.6 volts. Not sure on the 720 if the regulator runs both the temp and the gas gauges. (it does on earlier Datsuns) It's easy enough to take out and clean the contacts with fine emery paper. 1 Quote Link to comment
SUNRADER LANDON Posted August 11, 2016 Author Report Share Posted August 11, 2016 Hey y'all, what does this voltage reg look like? I cracked into my gauges last weekend and saw a bunch of wires and small bits when I pulled the face off the front of the fuel gauge. I should have taken a pic... 1 Quote Link to comment
SUNRADER LANDON Posted August 11, 2016 Author Report Share Posted August 11, 2016 Does the volt reg go bad and need replaced? 1 Quote Link to comment
datzenmike Posted August 11, 2016 Report Share Posted August 11, 2016 Looks like a set of points, and as such they can corrode or get dirty and just stop working. It's a bi metallic strip with a wire coiled around it and contacts on the end. When there is contact current warms the metal strip and it bends away and the contacts separate. It cools and makes contact and just keeps repeating this. Here's mine... There may be one for each gauge. A reference gauge setting is input and the regulator adjusted to read 1/2 or full or what ever it is. Just get some super fine emery paper and fold a thin strip so it's abrasive on both sides. Pull the contacts open, place the strip between the points, let them close on the paper, and slowly pull the paper out from between. This will polish the contact surfaces. 1 Quote Link to comment
SUNRADER LANDON Posted August 12, 2016 Author Report Share Posted August 12, 2016 Oh boy, I'm gonna have to study this image a bit. 1 Quote Link to comment
SUNRADER LANDON Posted August 12, 2016 Author Report Share Posted August 12, 2016 Idk datzenmike, I'm extremely inexperienced but very handy... What do I have to pull apart and polish in this pic? Is there any way you can point out on the photo? I hope this isn't asking too much. 1 Quote Link to comment
datzenmike Posted August 12, 2016 Report Share Posted August 12, 2016 It's at the very top in the picture. There is a small white wire coiled around the bi-metallic strip. (two dissimilar metals that when heated, expand at different rates and will tend to bend) At the far right of the strip is a pair of contacts, almost like ignition points... 1 Quote Link to comment
SUNRADER LANDON Posted August 12, 2016 Author Report Share Posted August 12, 2016 Oh I see it now!!! When I pulled my cluster I do remember seeing that. So would a light grit sand paper be too harsh? I don't have any Emory cloth lying around... 1 Quote Link to comment
SUNRADER LANDON Posted August 12, 2016 Author Report Share Posted August 12, 2016 But I do have wet or dry high grit paper.. 1 Quote Link to comment
datzenmike Posted August 12, 2016 Report Share Posted August 12, 2016 Sand paper but very fine. You want to polish the contact surfaces.... assuming this is the problem. 1 Quote Link to comment
SUNRADER LANDON Posted August 12, 2016 Author Report Share Posted August 12, 2016 I'm hoping so. If it's a sender unit or connection I'll have to burn through some gas then drop my tank! 1 Quote Link to comment
Charlie69 Posted August 12, 2016 Report Share Posted August 12, 2016 Hey Mike, do you or did you ever own an actual "Points File?" Quote Link to comment
flatcat19 Posted August 12, 2016 Report Share Posted August 12, 2016 I own a steel Emery board. It's a bit thicker than a 1/16" of on inch with fine knurling on both sides. Even has a point on the end I use as a pick. I remember as a kid my mom using one of these for her nails. I love it. Great tool in my box. Many uses. I have no clue if they can still be bought. 1 Quote Link to comment
Charlie69 Posted August 13, 2016 Report Share Posted August 13, 2016 Here this might help 1 Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.