Some possible electrical issues after replacing battery

trentbt1

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Jun 20, 2017
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Hey all, long time listener, first time poster. I have a 2004 crownline 202 lpx with a 350 mag. I bought the boat last year and by not knowing how old the battery was, I replaced it a month ago. After cruising around on the lake, I notice once my boat hits 150 on my temp gauge it bolts up to 230. I carry a temp gun and i'm not getting any temps at the sender or therm over 165-170. I've also noticed when I flip my captains call on it dumps my voltage to 9-10 volts and makes my temp gauge dip down about 40 degrees. I tested the battery and alternator myself today. Battery is running 14.2 volts when boat is running. Click on exhaust, alternator loses .2 volts, battery loses almost 2. I'm not sure what brand of battery I replaced but I put a autocraft marine battery with 1000 crank/800 cold. I've checked the main ground at the rear of the block, checked connections to starter and alternator, replaced a temp sender and nothing. The crazy thing that once it meets a certain resistance, it stays until the boat cools fully. Pulled the sender out last night after running, temp was 100 right on the end, gauge was reading around 150. The only other thing I've done to the boat this spring is I put a satellite radio tuner in the boat. It connects to the back of my radio. Has anyone had a similar issue or know what's going on?!?
 
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Bt Doctur

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Aug 29, 2004
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The main system ground is usually on a stbd motor mount bolt, from there thru the main engine harness plug, from there to the dash and may have another harness plug there, from there to the main daisey chain of ground wires to the gauges
 

Scott Danforth

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I would start at the battery connections that you just made since everything started when you changed the battery. clean everything so the battery and the connections are shiny and clean enough to eat off of. then seal them with marine electrical varnish. then move on to the block end of the battery cables, system grounds, etc.

remember, if the connection isnt clean enough to eat off of it, its not clean
 

Bondo

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remember, if the connection isnt clean enough to eat off of it, its not clean

Ayuh,.... Agreed,.... Shiny metal Clean,.....
 

gm280

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But use some type sealer AFTER you make the connection nice clean and tight, not before. JMHO
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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. then seal them with marine electrical varnish.

https://www.grainger.com/product/1D...5157!&ef_id=WLc_TgAAAP8QP_j5:20170621123037:s

Z_-tvzfo5oy.JPG
 

trentbt1

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Jun 20, 2017
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I just got done combing through every ground, cleaned battery terminals and the temp gauge is still being a pain in my ass. Boat is holding steady at 170, temp gauge reading 210 and moving when I turn things in. Could the new satellite radio dome installed over the dash cause some sort of interference in the gauge? That's the only other thing I can think of. Could it be the gauge acting up or does that sound too easy?
 

Benny67

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Apr 21, 2015
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Monitor your voltage at the Guage.

Put a voltmeter in parallel with the connections and monitor it and see what happens when it starts to read the bogus numbers.

I'm not sure of the voltage range you would need...I'd assume an auto ranging meter set to DC (obviously ) scale is what you would want.

Maybe it's just a bad guage....sometimes it's that simple
 

Benny67

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You would want to see a linear voltage increase as the temp rises
 

wahlejim

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Can you just eliminate power to the satellite radio? I am assuming you put a fuse in for the radio and didn't wire it inline with the gauges. I would pull the fuse and see what happens to eliminate that as a possibility.
 

wellcraft-classic210

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Are you still seeing less than 12 volts at the dashboard -- Things are unlikely to work correctly until that's fixed --

To get 12 volts to your dash with a properly working Battery and or alternator -- The Ground wire and connections from the dash area to the engine ( most likely the starboard motor mount ) is crucial along with a good 12 Volt positive wire and connections coming from the engine alternator. ( Battery to engine is only part of the circuit )

If the gnd is in question a redundant wire from the engine to the gnd on the dash can be added for trouble shoot but make sure its large enough for the load (#10 gauge should do it. )

If that's OK -- Try grounding the wire at the temp sensor on the engine and seeing how the temp gauge behaves ( The temp sensor is a variable resistor that decreases resistance when hotter increasing current through the gauge -- at 12 volts and 0 added resistance on the GND ( sensor omitted from the ckt ) the gauge needle should move all the way to the end of its travel ( opposite from no power applied )
 

trentbt1

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Jun 20, 2017
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Should I just look at the battery gauge to see if I have 12 volts coming to the dash or is there a better way to test it with a voltmeter? I took the rear ground off and cleaned it, disconnected the harness in the engine to check for corrosion and nothing. Pulled the positive cable from the started and cleaned it. Tested battery. 12.45 volts when off, 14.2ish while running, so that tells me my alternator should be working fine. I tested the sender this morning while I had the boat in the water, the resistance values are where they are supposed to be, I tried grounding the sender to the block and didn't change the temp. I did pull the sender wire and grounded it to the block and it pegged the gauge. It's just so odd that the gauge is reading solid at 210 and my sender is showing 168 on the IR gun. I just hate not having a properly working temp gauge!!!
 

Benny67

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It's just so odd that the gauge is reading solid at 210 and my sender is showing 168 on the IR gun. I just hate not having a properly working temp gauge!!!

Did you see what the voltage is at the gauge?

Does it vary voltage when the engine is cold to when it's warm and then when it's giving you a wacky reading?

If the gauge is not working the way you want it,why not confirm at the source first that you do in fact have or not have the proper signal to make the gauge work correctly?

THEN you can work your way back through connections and wires...but confirm at the source that the gauge is working properly first.

The connection you feel about the radio interference (RF) is highly doubtful....unless the install caused the gauge to have a bad connection via human interference....meaning the installer knocked off a wire connection or did something else screwwy.

Just my $.02
 

trentbt1

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Jun 20, 2017
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I've tried searching for resistance ohms for my temp sender and can't find them anywhere. I have a voltmeter in my boat and I've got readings, I just don't know how accurate they are. I'll check to see if my gauge is getting 12 amps and maybe go from there. Any idea what ohm setting I use to check for resistance? I'll double check what the gauge is showing but at idle i'm pretty sure it was between 12 and 13.
 

Benny67

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Do you have a wiring diagram. If not, get one.

Determine what wire is ground on the erroneous Guage and see if it has 0 ohms resistance directly to the battery ground. Use your lowest setting resistance if it's not an auto ranging meter.

If it's open (infinite resistance) there's your problem....most likely you will either see a few ohms or none at all...none at all is good...a few ohms is not so good

(resistance=voltage drop= bogus readings on your gauge)

My personal thoughts are it's a bad/coroded crimp or a bad guage.

If you have continuity (0 resistance from battery to - on the gauge) then take the wire from the temp sending unit out of circuit (disconnect + from both the gauge and sending unit)
and check for continuity between the two. Again, there should be little to no resistance. If there is resistance then that could also be your problem.

Post your findings if you choose to take that path of troubleshooting.
 

wellcraft-classic210

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Your battery gauge may be reading OK -- But the only way to know for sure is to check/ compare with a Multi-meter--

Try running a Gnd wire from the engine block to the Neg of a Multi-meter lead and the + side lead to the + on the boats voltmeter gauge- ( Meter set to dc voltage ) -while powering on a few items - if you get similar readings between the Multi-meter and the boats voltmeter you can trust your gauge -- if your staying at 12-14 volts that's indicates all is well for dc power supply and then you can start working on the individual components.

( PS -- voltage drops seen with trim and starter motor are normal on most boats due to their high current draws -- but +12v - +14V should be seen at other times )


If all that checks for trustworthy voltage etc and your still getting strange readings at your temp gauge -- -

- Are the gauge and sensor are a matched set? ( As in compatible with each other ) (The sensor resistance at a certain temp must provide the proper amount of current through the gauge )

--Is the wire between the gauge and sensor connecting to anything else the could add to the current draw?

-- Any chance the needle was moved on the gauge ?

Also
It does appear the the temp gauge is functional by your recent gnding test -- But the devil may be in the details calibration/ temp accuracy


Keep us posted & good luck !
 

bruceb58

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Start your engine, get a long test lead and measure the voltage between the positive post of the battery and the positive post at your console fuse panel. Then do the same for negative to negative. You should be getting very low voltage numbers and each side should be around the same. If you don't and/or either number is more than 0.5V, you need to identify where the drop is.
 

Benny67

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I've tried searching for resistance ohms for my temp sender and can't find them anywhere.

Don't worry about that yet.

The resistance of the sensor varies with the temperature of the motor...It decreases as the motor heats up...when it does increase the voltage to the Guage increases. ..that in turn causes the gauge to increase in its range...see where this is going?

Cold motor = high resistance in sending unit= low reading on gauge
hot motor= low resistance in sending unit= high reading on the gauge
 
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