Since you ordered 2 hall effect ammeters, know that the instructions say each display is calibrated to the sensor it arrived with and not to mix them up.
I added about 6 feet of wire in the center of 3 wire ribbon cable. The ring sensor should not be exposed to the elements. I did not want To put mine in engine compartment and didn't.
Might want to find somewhere to put ring sensor while you wait for their arrival. Or a way to shield it from radiant heat and moisture, and perhaps within the 2 meters distance of the ribbon cable length they provide.
On mine, The voltage display was 0.2v off. Low, if i remember correctly, but i have it set to display only amperage as i have separate voltmeters with sense leads to battery that can be calibrated.
You could wire yours to read fuel pump voltage. You then might see its connector getting sub 10vdc due to undersized wiring and 29 year old high resistance connections that get only worse in the high ambient heat where your problems arise.
Order yourself some caig deoxit d5 or d100 and clean every connection on the fuel pump circuit.
I was more interested in the hall effect ammeter link which also displayed amp hours and watt hours flowing unidirectionally. Just saw that product first time yesterday.
My ~ 15psi system in tank fuel pump on my 89 dodge la318 tbi is about 4.2 amps.
