The right hand light is supposed to be for oil pressure. Should be green. The red on the left is for charging. Assuming yours is diesel, the sender is on the left side of the engine close to the injector pump.
Remove the sender and plumb in a manual gauge to see if in fact you have an oil press problem. Think i had to use an elbow to make it work. I repaired the light on mine and then it stayed on all the time. I actually had around 60 psi oil pressure, so I got a new sender from NAPA. They do go bad. Hope that's all thats wrong with yours.