Hi Jim;
The oil temperature circuit in you Cherokee is a very simple circuit. Aircraft power is picked off the main bus, then routed through the windings in the gauge. The voltage across the windings causes the needle in the gauge to move. From the gauge a wire is routed to the temperature sender, which is screwed into a bushing in the engine.
Let’s start with the easy trouble shooting. Check to see that the wire to the sender in the engine is intact. Look for a loose wire, or a broken wire. If it does, simply repair the connection.
If the connection looks good, then one possibility is that the sender has failed. Senders can be tested by removing it, and connecting the center wire connection to an ohm meter. The other lead from the ohm meter should be connected to the body of the sender. The resistance of the sender will change with the temperature it’s submerged in. If you have a soldering iron or even a wooden match, apply heat to the end of the sender. Does the resistance change with variations of temperature. If it does, then the sender is probably good.
The part number of your sender is 462-046;
The next check is to see if there is aircraft power on the gauge. This can be done with a voltmeter. The voltage should be the same as the voltage on the aircraft bus. If there’s no power, find out why.
If there’s power on the gauge, and the wire between the gauge and sender is intact, then the gauge has failed. You can get the gauge repaired at:https://www.airpartsoflockhaven.com/cluster-gauges. I found a used one on eBay.
Due to the original suppliers (A.C. and Stewart Warner) suspension of production, Piper issued Service Spares Letter 406. This letter notified suppliers that Piper was no longer sending the original parts; that the “cluster” gauges had to be replaced with gauge sets (gauge and sender) made by Rochester. The part number for the Rochester gauge is 87366-2; for the sender it’s 553-672. These replacements fit in the original spaces and use the same wire.
I hope this guides you in solving your oil temperature problems.
Happy Flying,
Steve
