Troubleshooting Inop Oil Pressure and Temp Gauge

[SP3]

Did a search here and not finding any hits on method to resolve.

Are there other ways to troubleshoot the combo Temp/Oil Pressure gauge on a ‘67.5 beyond grounding the lead that connects to the Sender?

I have new Senders on both and when tried grounding neither swept to the left.

Initially when installing the Sender for OP gauge it would move 3/4 to left and then slowly return to right - 0 and then not move.

Temp gauge never moved after replacing Sender in Head.

[Habitat.pat]

Does your fuel gauge work? The temperature & fuel gauge use a regulator on the steering column.

That does not affect the oil pressure gauge though.

I haven’t looked, but I don’t think the temperature & oil gauge require a ground.

Probably 2 different problems. Oil pressure gauge power?

Peace,
Pat

[Habitat.pat]

Looks like my wrong reply went out. The two gauges use the same fuse. If it is a problem with the fuse, turn signals should be out too.

Peace,
Pat

[Gregs672000]

As noted, the oil pressure is separate from the temp even though it's on the same gauge. The resister mentioned affects the fuel and temp gauge read out but has nothing to do with the oil pressure. If the fuel is reading normally your issue is likely the temp sender. A bad ground often causes this, or a bad sensor (if both fuel and temp are not working then check the resister). Test the sensor by grounding it and it should go full hot. If so, you need to ground the sensor case. This can be accomplished by adding a wire or pulling apart the housing and replacing the gaskets which have grounding tabs built into them that can go bad. I can post a pic showing the wire fix if needed.

Early electrical oil pressure senders are prone to be very poor indicators of true pressure, even new. If it moves you have pressure. I hooked up an aftermarket mechanical oil pressure gauge and it showed plenty of pressure under all conditions while my stock read out was barely above 0, max ever is the middle of the gauge. Replacements for the sender are stupid expensive so I just know it's ok when it moves and I don't worry about it anymore.

[SP3]

Yes Greg,

If you could post a picture of the wire fix to the Temp gauge. I tested both gauges by grounding out their leads and both rapidly swept to the right, so looks like gauges are working.

[Gregs672000]

Here's a pic. The housing is off the head right now as I'm getting some work done, but this should show you what can be done. Not as "pretty" as using the stock gaskets with the metal tab, but easier than draining some water, redoing gaskets etc. More reliable in my opinion too. Just bare a length of wire, wrap it around the holder the sensor sides into and secure it with a thin zip tie, then bolt the other end to one of the studs and you're grounded. Alternatively you could buy new gaskets from a vendor, or make your own using the proper gasket material that is for water and recreate the metal tabs with thin wire... but after 35 years you see why I just go with the wire. You can do this fix for now and wait until you need to do some work on it to do the stock gasket, just make sure you don't cover the metal tabs on the new gaskets with sealer or it won't ground if you do.

[Habitat.pat]

I didn’t see whether you have a 1.6 or 2L. The fix Greg shows is for the 2L only.

Peace,
Pat

[SP3]

Yep, it is a 1600. I get the idea and will see what can be done similar. Presently radiator is drained with water tower off motor.

[Habitat.pat]

The temp sender on the 1.6 is in direct contact with the head so there shouldn’t be a problem with that. If you ground the sender lead & it pegs the gauge, the sender is bad. The sender is held in by a nut around it. If it is stuck to u will need to drive the sender out with a punch through the hole where the tower bolts on.

Peace,
Pat

[Gregs672000]

The temp sender on the 1.6 is in direct contact with the head so there shouldn’t be a problem with that. If you ground the sender lead & it pegs the gauge, the sender is bad. The sender is held in by a nut around it. If it is stuck to u will need to drive the sender out with a punch through the hole where the tower bolts on.

Peace,
Pat

Yes, I assumed it was a U20. But Pat, you're saying the sender is different from the U20 One? I have not looked at all, but I would think they would operate the same way, with the sender being held in by the sleeve (that the wire wraps around) to provide the ground to the metal stud. On the U20 if you ground the sender and it pegs then it's good, not vice versa. He's replaced the sender... I'm Confused!

[Habitat.pat]

Greg. The sender is held by the nut/sleeve, but it threads right into the head. The 2L sender screws into the elbow which can be insulated from the head by the gasket without the staple & rust. The grounding of the elbow is what the wire generally does. I’ve never heard of the sender not grounding to the elbow although I suppose it could happen. I didn’t see that he replaced the sender. If so, more troubleshooting is in order.

Peace,
Pat

[Habitat.pat]

After looking back @ the original post, I see that you have a new sender installed. It is possible that it is defective or there is a bad connection. Check the resistance between the sender terminal & the head. I’d have to look to see what normal is, but it shouldn’t be an open circuit. If it is, next check between the sender case & the head. It should show short. If not, check between the nut & the head. It should show a short.

It wouldn’t hurt to check between the battery ground post & the head just for grins.

Please let us know what you find.

Peace,
Pat

[Gregs672000]

Greg. The sender is held by the nut/sleeve, but it threads right into the head. The 2L sender screws into the elbow which can be insulated from the head by the gasket without the staple & rust. The grounding of the elbow is what the wire generally does. I’ve never heard of the sender not grounding to the elbow although I suppose it could happen. I didn’t see that he replaced the sender. If so, more troubleshooting is in order.

Peace,
Pat

Thanks Pat! Hope to see us both on the road again soon!

[Curtis]

http://kendo-usa.org/datsun/datsun_gaug ... t_67_5.pdf