TAMD41D Temp alarm and gauge problems?

I have a newly rebuilt TAMD41B. When we started the new motor the temp gauge never read above 100F and the alarm started to whistle as soon as the motor warmed to the touch.

I checked grounds, multi-pin connections at the gauge cluster and the motor, re-crimped cleaned and re-attached the wires at the senders on the thermo housing, etc. The needle on the gauge moves when the ignition is turned on but never reads over 100F.

I disconnected the brn/wht wire (alarm?) at the forward sender and the alarm quit. I also tried disconnecting the tan wire (gauge?) at the aft sender. Nothing has worked.

How do I troubleshoot this problem? Is there a bad/good resistance reading I should be getting when I jump the sender wire and sender with the ignition off using my voltmeter? Do I need to drain coolant to replace senders?

I suspect a ground fault, but all appears well?? Is it the gauge, senders, or...?

Also, my tach jumps up to 5000 when I start the motor and bounces all over for 10-20 minutes before it settles and reads properly. It has done this for years. Is it a bad tach or faulty ground or ...??

Many thanks in advance for your help!!

-GS

I am guessing that you have wires on correct senders. Alarm is the one with a larger hex base where is screws into housing. Gauge sender with ohms meter attached will change resistance when engine warms up. Switch should be open until overheat occurs. Check ground wire to block from alternator ground post. Clean and tight.

Thank you for the input! BTW...motor is a TAMD41D not B...my mistake!

The wires to the sender and the gauge were reversed. The tan colored wire is the gauge wire and it goes on the forward sender of the 2 mounted on the thermostat housing. The brown/white wire is the alarm sender and it goes to the aft sender on the thermostat housing.

I checked the wires by grounding to the block with the ignition in the accessory position. The temp gauge pegged when grounded, and the alarm rang when the alarm wire was grounded. I noticed the hex-shaped sender with single wire connection had 120 degrees stamped on the hex and this was how I figured the wires were reversed.

I'll double check the ground connection on the alternator. The tach bounces all over the place before it settles in and reads properly. It even pegs the tach when the ignition is turned on, then settles after running for 10-20 minutes.

Many thanks for the comeback Vosman!

-Kawakawa