I upgraded my instrument panel to the combination tach/speedo unit(1988 22RE). Also put in the proper sending unit for the oil pressure guage. I am not registering oil pressure. My FSM says to connect a 3 1/2 watt bulb in the line and check for a pulsating signal to validate the sender as working. My check light has a 5 watt bulb. Before I do this I want to be sure I don't cause any damage to the sending unit in case that's not the problem. It also says to use a 3 1/2 watt bulb to check the guage. I'm afraid of damaging that unit, too. Any thought here whether using the 5 watt bulb could cause any problems?

Hoping someone here would be challenged enough to answer this question. Any help out there? <img src="/forums/images/graemlins/confused.gif" alt="" />

I'm assuming that the 3.4 watt bulb specified is sized to closely match the resistance of the gauge sender or 44 ohms as per the FSM. At 12 volts, 3.4 watts is about 42 ohms resistance. A 5 watt bulb is more like 28 ohms. Not sure whether that difference is significant or not, but you could always add a resistor in-line to make up the difference and limit the current in that test circuit.

4Crawler, I think I will have to find a 3.4 watt bulb and base and rig a test light. I guess I'll also be checking some test lights for their wattage. Thanks 4Crawler for the reply.