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Temp gauge not working

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bronc

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Have a 2003 M/C 5.0l,Searay 300 sundancer, Temp gauge not responding, replaced thermostat, switched temp sensor from other engine to not working still nothing. The gauge is in a cluster with one gauge working /reading, oil, volts,trim position. When I turn the engine seitch on the gauge moves ever so slightly. Checked in the back of gauge , everthing seems tight and no rust. Any suggestions would be great.
 
Ground the engine temp sensor w/ignition on...if all is good the gauge should peg to max temp. If it doesn't then go to the back of the gauge and again ground the same wire on gauge that is on the sender. If it doesn't peg to the max temp the gauge is faulty. If the gauge pegs then the problem is between the gauge and the sender. Clean the wire to the gauge connection w/light sandpaper. Pull the engine barrell plug off and look at the pins for corrosion.
 
Thank you. I tries everything, the temp gauge does peg when grounded. Should I know replace the wire?





guyjg said:
Ground the engine temp sensor w/ignition on...if all is good the gauge should peg to max temp. If it doesn't then go to the back of the gauge and again ground the same wire on gauge that is on the sender. If it doesn't peg to the max temp the gauge is faulty. If the gauge pegs then the problem is between the gauge and the sender. Clean the wire to the gauge connection w/light sandpaper. Pull the engine barrell plug off and look at the pins for corrosion.
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With power on (key in run position) if you briefly touch the sender post on the guage to the ground post the guage should peg!

If it does not replace the guage..................
 
Yes the gauge does ped, I have swiched sending units from the one engine that works to the other, I have cleaned both sending units and sanded the corrision off. The gauge did peg but when startedthe eng still no temp gauge working, thanks
 
Then there is a connection between engine and guage that is bad.


Start and run both engines for a while that would typically warm it up to at least 120-140 degrees.

if you have a digital volt meter then select OHMs and disconnect the sending wire at the sending unit on each motor, connect one lead to the post and the other to the body of the sending unit Not an engine ground. Take a reading. the sending unit is ~ 60 - 240 ohms so you would expect to see ~ 130 ohms (guestimate)

If you get approx the same reading from both now go to engine ground and see if it is the same again. If not the threaded hole is not making a good ground at the sending unit.

If it is the same (approx) then go to the guage for each and diconnect the sending wire from each guage, attache one lead of the meter to the sending wire and the other to ground. The ohms reading should be the same or very close as the readings from the motors for each motors guage. If the one in question is not the same then it is a wiring issue, Most likely either a bad connection at the main wire harness plug or a damages or pinched wire somewhere......

is the same guage used for both motors? do I understand this correctly? What exactly does the switch, switch?

One other question? where is the sending unit located? Is it threaded into the block or the thermostat housing.

If it is threaded into the thermostat housing the base gasket has brass star washers that make continuity from the block to the housing. If that area is no longer clean the ground may be hindered. Try grounding the sending unit body to battery ground with a jumper and see if the guage works.......if it does then it is the base gasket.
 
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bronc said:
Yes the gauge does ped, I have swiched sending units from the one engine that works to the other, I have cleaned both sending units and sanded the corrision off. The gauge did peg but when startedthe eng still no temp gauge working, thanks
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Swapping the wires on senders won't tell you the answer. One is a "sender" for the gauge and the other is a "switch" for the alarm and is an open / closed switch, not a variable sender. If you ground the wire at the sender and the gauge pegs, then either the sender is kaput or the ground on the housing is bad.

Get a good ground on the housing with a jumper wire from it to a good battery ground and see if that makes it work. Did you have that housing off? If so, was the gasket with the 2 rivets on it used between the thermostat housing and the manifold when replacing with NO silicone. Silicone can insulate the ground path to the manifold even when the riveted gasket is used..

Let us know what you find.
 
04fxdwgi said:
Swapping the wires on senders won't tell you the answer. One is a "sender" for the gauge and the other is a "switch" for the alarm and is an open / closed switch, not a variable sender. If you ground the wire at the sender and the gauge pegs, then either the sender is kaput or the ground on the housing is bad.

Get a good ground on the housing with a jumper wire from it to a good battery ground and see if that makes it work. Did you have that housing off? If so, was the gasket with the 2 rivets on it used between the thermostat housing and the manifold when replacing with NO silicone. Silicone can insulate the ground path to the manifold even when the riveted gasket is used..

Let us know what you find.
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He has dual motors, not refering to the sending unit and over temp switch I dont believe..........I think he is refering to one sender on one motor vs the other and I think he has a switch to change motor 1 to motor 2 for gauge cluster..........I think.

He is not 100% clear
 
Yes I took the good sender/sensor that is working and reading properly off the port eng and switched it to the stb eng. Still doesn't work. I replaced the theromstat with the rivet gaset and no silcone just gasket. Each eng has there own sending unit, 5.ol m/c B3. Sending unit is located it the thermostat housing and it's a screw it type. Seperate gauges for each motor.
 
Sounds like a ground issue at the gaskets......try tightening the thermo housing bolts or run a ground jumper from the sender base to battery ground and recheck, Pull the sender out, connect the sending wire to the cenetr post, connect jumper from threads to battery ground and hit it with a hair dryer or bic lighter and see what happens... (of course the heat goes to the base of the sendoer not the top...........)
 
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kimcrwbr1 said:
I`m thinking the thermostat housing is not grounded to the engine maybe try putting new lock washers on the bolts for the thermostat housing. To check if the sender is grounded short the guage wire to the base of the sending unit it should peg the guage hot?
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I don't think a lockwasher will to it, since there is a gasket above and one below the housing, insiulating it pretty well. I drilled and tapped my housing (not in the water jacket area, if you were wondering) and ran a ground wire directly from the housing to good ground. Eliminates need for the riveted gasket, also.
 
Your roght Its a ground issue. I ran a jump wire from the port engine to the wite on the stb engine and the gauge went right to 160 or so. All the grounds on the engine look ok and are tight. Maybe a new ground wire will work. Thanks
 
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