Temperature gauge resistor

[Catrik]

Chevy K10 with 6.2D, following this guide http://forum.73-87chevytrucks.com/smforum/index.php/topic,25339.0.html

Using gauge normally -> pegs hot
Disconnecting wire from sender and grounding -> pegs hot
Place 105Ohm resistor between sender wire and ground -> pegs hot

I now have the gauge removed. I gave it 12V (12.00V, not ~12.7V from battery, not sure if this should make any difference) and it still pegs hot when I connect the 105Ohm resistor between ground post and sender post. I then removed the large resistor from the gauge and it reads open connection (as pictured).

So it seems like I  need to replace the resistor, but I can't find info on what value a green one should be. Any idea? And can I just use any wire resistor with >3W rating?

[VileZambonie]

What do you mean using the gauge normally? Are you saying it's pegged hot at all times? What does the gauge do when you open the circuit key on engine off?

[Catrik]

What do you mean using the gauge normally? Are you saying it's pegged hot at all times? What does the gauge do when you open the circuit key on engine off?

Using normally as it is installed in the vehicle with wires connected, it is pegged hot all the time.

The gauge never goes down, unless I move the needle by hand. So if I open the circuit by removing wire from sender, the needle doesnt move anywhere by itself, in any key position.

[VileZambonie]

So key on engine off, taking the wire off of the sending unit does not change the gauge position and grounding the wire does not change the gauge position?

Is the 20A gauge fuse good? Do you have 12 V at the pnk/blk wire at the gauge cluster with the key on?  Check continuity to ground at the dark green and the integrity of the sending unit wire.

[Catrik]

Wire off sending unit = gauge position does not change, I can move it by hand and it stays there.
Wire grounded = pegs hot.

I have 12V at gauge cluster. I'll double check ground and sending wire.

[Catrik]

Only took me two months but I finally double checked ground and sending wire at gauge cluster and they seem to be working correctly. I also got a new sender since I was ordering other parts anyway. Hooked it to ground and connected to sender wire but it makes no difference.

Anyone know if the stock sender will work with aftermarket gauges?

[bd]

The calibration of a sending unit needs to match the gauge to which it connects for the gauge to function correctly.  For a generic gauge to be compatible with an OEM sender, the gauge manufacturer should state that it is in the gauge description.

Don't overthink this problem.  The OEM temperature gauges are really simple.  If the gauge receives 12-volt power (B+), a good ground connection (B-), and an uncompromised sender connection (bearing in mind, of course, that the sender housing or case and gauge must share a common B- connection with the power source), the gauge will indicate in accordance with the resistance of the sender.  So, if you verify B+, B-, and sender in all of the proper places, then all that remains is a faulty gauge assembly - no?  Forget what you've done so far and recheck everything.  Use the diagram posted by VileZambonie as your guide.

FYI - HIGH sender resistance = COLD temperature gauge indication, LOW sender resistance = HOT temperature indication.  In a practical sense, this translates to a COLD gauge reading if the sender wire is disconnected from the sender and a >>> HOT gauge reading if the sender wire is grounded.