Temp Gauge Help

[WellFast210]

Hello all,

Just installed a new set of Teleflex Lido 7 piece gauge set. All work great except the engine water temp. Old one worked fine.

Tests I have performed:
-Verified all connections, S, G, and I.
-Pulled off signal wire at sensor and touched to engine ground. (needle on gauge instantly went to max position).
-Connected digital volt/ohm meter to sensor, then held sensor tip in hot water. Can't recall the exact numbers, but were within specified range and fluctuated with temp.
-Grabbed old gauge, heated up sensor, attached some pigtail wires, and held on car battery. (hot water from coffee pot, gauge starts at 120deg. Gauge read 150+ and was climbing).
-Hot sensor on new gauge in boat. Gauge also starts at 120deg. When connecting signal wire, gauge needle goes from slightly below 120 (max lowest position) to just slightly above the 120 hash mark. But needle does indeed move.

I believe the thermostat is 160deg. Engine is a 1994 Mercruiser 5.7L LX with the Thunderbolt Ignition, and audible warning system. This adds another sensor on the opposite side of temp sensor. But really don't believe this to be any problem.

Want/need exact ohm readings? I can get them again. Pics/video, whatever it takes.

There something else I can check or tests I can perform? Would hate to throw down for another gauge to have the same existing problem. Kinda stumped. Please, any info or advise will be greatly appreciated.

Thanks.

 

[sam am I]

Guessing your new gauge is expecting a 450 ohm - 30 ohm (100F-250F) sender and your current sender is for the old gauge expecting a 1600 ohm -100 ohm (100F-250F) sender for example.

This to me, sitting in the back seat driving the boat explains why it(the needle) went up slightly when cool'ish(1600 ohm verses 450 ohm), then crapped out(hardly/didn't move) as the temp went up(100 ohm verses 30 ohm). The dr/dt (change in resistance over change in temp) of the current sensor w the new gauges scale(F.S. deflection) is not matched.

You should be able to confirm my guess with your ohm meter with known water temps in the engine, w graph and old sender, @ 150F, your sensor might be around 1100 ohms. 310 ohms is what your new gauge requires here to read accurate/properly.

.........or skin the cat on the bench short of having all the paper work and such to tell you, and if you have them laying around, power up the gauge as you did and hang a 310'ish ohm resistor to ground off the new gauge to ground, see if it goes to 150 F. Then hang a 1100 ohm resistor to ground off the old gauge to ground and see if it goes to 150 F, if both act as I guess they will, the sender is wrong type for the new gauge. .......just guessing ya know

Edit.......Correction in values/test method, added graph(below). Blocked out during typing/editing when "read only" occurred .......apologies for latent update.

 

[sam am I]

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