I can tell you that the oil temp gauge has a sender in the block and the gauge itself; that is all there is to it. I would think that if you grounded the lead going to the sender (with the key in the ON position) the gauge needle will either peg left or to the right. Now if you used something like a 100 ohm resistor, on the sender lead, the gauge should show somewhere in between.
I do not know the resistance range of the sender; it may be stated in the 81 Service Maual, would have to look. If you get no response out of the gauge at all, then either the wire is broke between the sender and the gauge or the gauge iteself is toast.
I know you can get new senders from GM still; I can get you the part number if needed.
Update to this problem, I finally got my assembly manual and started picking at this problem. Come to find out my "Oil Temp Gauge" does not work because the oil temp sending unit is connected to the wrong gauge, the "Engine Temp Guage"! So the problem is not whether or not my "Oil Temp Gauge" works, which when I hook it up correctly I hope it works. It looks like my "Engine Temp sending unit" is not wired up or does not work.
I need to take my dash apart, Arrrgh, (that is going to be a long day) and straighten this mess out. And to think I have been watching my Engine Temp Gauge as if it were my oil temp gauge, knowing it was the oil temp I was monitoring and not realizing it was on the wrong gauge. Geesh, even I didn't understand that sentence.
I have looked through the assembly manual but can not find where the engine temp sensor is located. Any clues as to where to start looking would help out a lot.
The oil pressure sending unit's resistance goes up as pressure goes up, therefore if you ground the gauge lead at the sending unit the reading should go to zero.
I did this and the needle pegged to the left, not to zero.
Just disconnected the connector from the "Oil-Pressure Sending Unit" and the needle immediately pegged to the right past 80 when I turned the aux power on, and stayed pegged as I started the engine.
>>but the temp gauge sender is usually in one of the cylinder heads (probably driver's side).
Would this mean it will be much harder than messing with one of these other sending units? Man, I wanted to troubleshoot this tonight and get it over with. Can anyone confirm the location of the "Temp Gauge Sender"? And what it would take to get to it and troubleshoot it.
Wait a minute, I'm getting confused here. When you remove the oil pressure sending unit connector the gauge should peg, that's what I would expect. Now when you ground the sending unit wire that goes to the gauge, the needle should go to zero. If the gauge is pegged whether the wire is grounded or disconnected then either the gauge is bad, the circuit is open between the sending unit and gauge, or you have the wrong wire.
The temp sending unit should be easy to get to. look on the side of the driver's side cylinder head between the exhaust ports for cylinders #1 and #3. It will have a single-wire connector, usually a spade-type (again I'm not sure exactly for an '81, but this is typical). If you don't see it on the driver's side head then check the passenger's side between #6 and #8.
It sounds like I have totally confused not only myself but you also. I am going to start over with the troubleshooting:
The oil temp sending unit is working through the Engine Temp gauge.
I am sure your earlier statements on how to troubleshoot the oil pressure sending unit are correct, I will redo this part again tonight since I really have confused it badly.
The oil pressure gauge works fine. Reads around 40 and works upto 80 during driving since I have a rebuilt engine with a high pressure oil pump.
The Engine Temp sending unit does not work. The gauge like above works since the oil temp sending unit is wired to it. But I have no Engine Temp where the oil temp is. This little fact has litterally confused me badly while troubleshooting this. Sorry for really mucking up your statement.
So where I am at now is I need to start figuring out if the Engine Temp sending unit works. Where would I locate the Engine Temp Sending Unit?
Just got back from my first corvette show! A local corvette club show for Lafayette, LA. There must have been about 100 cars in the parking lot. Mine was one of them :gap . Was a lot of fun and I met several people from the area. I guy even showed me exactly where the temp sending unit was! I really can not express how great it was to be around so many corvette related people. I am sure you know exactly what I am talking about. It was great. I will be troubleshooting more in the morning and will let you know what I find out.
Where can I get a replacement if this is the problem?
OK here is the news,
Got under the car today to look for the oil-temp sending unit. There is not one. Although I did find the connector for it, and put a 100 ohm resistor to ground on it. It gave me a reading of about half in temp on the gauge! Great, so that means I am half way there, the gauge works so the sending unit must be the problem. But, there is no sending unit between the last two exhaust ports on the drivers side, but there is an Engine-Temp sending unit between the front exhaust ports on the driver's side. This sending unit works great. Can this sending unit be used either or for Engine Temp and Oil Temp? or Does the location of it really matter?
How can I not have an Oil-Temp Sending Unit? Does this mean my engine is not a L81? The assembly manual drawings do not even note the location of the engine temp sending unit. Which as I found is located on the driver's side front of engine. Boy, this worries me now.
Can someone comment on what they think is going on here with my engine?
Any ideas on where to go next?
This is my fault...I misunderstood and thought you were looking for the cooling temp sending unit.
Look around where the oil filter attaches to the block, the oil temp sender could be in that area (it is on an '84). If the connector is in that area and you find a plug in the block near the oil filter, then I guess just buy a sending unit and install it there.
I looked near the oil filter where I found the connector and can not find the sending unit anywhere. I have also looked for a plug, but can not find that either. I took the spark plug heat shield off to get a better look around this area, but nothing. I'll keep looking.
There is a small plug right above the oil filter. About 1 inch above where the filter screws into the block. The plug is in a place for the connector to reach perfectly. It does look smaller than the engine temp sending unit hole though.
what do you think? My engine was rebuilt and the plug has never been taken out since it was painted blue. If this is the plug do I have to drain the oil before I can take this plug out?