Recently, some of our customers have brought to our attention that they are having problems calibrating their senders or that their gauges were reading improper fuel levels or not registering at all. Although we are still investigating the issue we have been able to determine some problems with respect to why gauges and senders are giving false readings. If you are having issues please read below.
Symptoms:
When turned on, the gauge needle goes past Full/Empty and remains, even with no fuel in the cell.
There are a several things that could be going on here. First, the sender itself may not be calibrated. We usually leave it up to our customers to calibrate the senders when they get them, so if you purchased a fuel cell and did not calibrate it this may be the problem. Follow the calibration instructions on our Guides page to complete it.
Second, the wires may be backwards. If you have the SEND and NEG wires backwards this would cause the gauge to constantly read Full or Empty (depending on the gauge and manufacturer). Trace the wires back and make sure it is hooked up properly or take a Voltmeter and test the wires (SEND should read 0.0V when disconnected from the Sender on 3-Wire gauges and should be positive on 2-Wire gauges).
Finally, the gauge and sender may be incompatible. The first thing to due is make sure that the gauge and sender are the same ohms (0-90, 240-33, etc.); if they're not then there will always be a false reading. If they are the same ohms the next step is to determine if the gauge is a 2 or 3-Wire gauge. Gauges from companies producing products for marine application, such as Livorsi, are usually designed as 2-Wire gauges. This means that you'll need a 2-Wire sending unit (one with only 2 posts, NEG and SEND). Other manufacturers, such as AutoMeter, produce both 2 and 3- Wire gauges, but the latter is more common in modern vehicles. If you're still not sure you can determine which kind you have using a Voltmeter. For 3-Wire gauges the SEND wire coming from the gauge will have no reading on the Voltmeter, neither in Volts nor Ohms. For 2-Wire gauges there will be a positive volt signal (usually around 6-8 volts) on the SEND wire coming directly from the gauge. Once you've determined what type of gauge you have check the posts on the sending unit to see if it has 2 or 3 posts (indicating 2 or 3-Wire compatibility).
When full, the gauge needle bounces back and forth between 3/4 and Full.
This has been a more recent problem with senders and usually occurs between AutoCal senders connected to the new line of AutoMeter Programmable Empty - Full Range gauges (can be programmed for any ohm range or custom range). What is happening is the Full Detection unit in the sender is not registering a correct Full with the gauge. There are a couple of steps to take. First, make sure that the ohm selection on the gauge is correct (is set to the same as the sender). For example, if the sender is a 0-90 make sure the gauge is set to read 0-90 (follow instructions to switch reading range). If this does not fix the problem, try following the instructions for setting a custom range in the gauge.
If this does still not solve the problem try manually recalibrating Full on the sender (same procedure for AutoCal and non-AutoCal programmable senders). If the problem persists, the only solutions will be to replace the gauge with another or to replace the sending unit with an older-style one.
The gauge needle registers past Full and past Empty.
This usually indicates that the sending unit is not properly calibrated or tuned with the gauge and will need to be recalibrated (Click here for instructions).
The gauge turns on but the needle does not move no matter what the actual fuel level.
There are a couple of things this could be. First, the wiring may not be correct or the gauge may not be connected with the sender. This is usually the case and a simple re-wiring or re-connecting the wires will solve the problem.
If both the gauge and the sender are hooked up properly but there is still no reading there is either a defect with the gauge or with the sender. To determine which is at fault you will need a Voltmeter. For 3-Wire senders connect the POS and NEG but not the SEND. Turn on the power, turn the Voltmeter to Ohms, touch the negative electrode to the NEG post and the positive to the SEND. If the sender is working properly, there will be a reading coming from the SEND post. For 2-Wire gauges a similar process can be performed on the gauge. Connect power to the gauge but do not connect it to the sender. Connect the Voltmeter to the NEG and SEND wire coming from the gauge and turn it to Volts to make sure there is a signal coming from the gauge. With 2-Wire gauges the SEND wire from the gauge both powers the sending unit and registers the ohms; so no power in the SEND line means no power to the sender. If everything checks out but still no response from the needle, then the gauge is faulty (nearly all gauges do a range sweep when powered up, even if not hooked up properly to the sender, so if there is no response from the needle when first turned on then chances are the gauge is defective).
In most cases, these issues can be easily overcome by simply recalibrating the sender or replacing the gauge/sender with one that is compatible. To avoid these problems altogether please specify what gauges (manufacturer and ohms) you will be using when you order a sending unit or fuel cell, what type is it (2 or 3-Wire) or send the gauge to us directly when you order a fuel cell or sending unit so we can calibrate it, or send the gauge and sending unit to us directly (if you've already purchased both) and we'll calibrate them.
If you still have questions or issues not covered here please contact us directly.