Lowrance GPS Question

Bantle

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I have both a Lowrance 540c and Lowrance 7200 in the race truck wired to the same power source. The problem is the 540c will turn off when the starter is engaged while the 7200 will remain on. Both units are wired identically and I can find no reason why one turns off and the other doesn't when starting the motor. Is there a setting within the GPS unit menus to fix this or is this how the 540c is supposed to operate? Any help would be great it is starting to get annoying.
 

Desert_Roller

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Sounds like your 540 is really voltage sensitive, at or around 12 volts is it, they will not power up or stay on below that.

Either you have a high compression engine or your battery(s) do not have enough cranking amps or both?

Try a re-wire taking the units directly to the battery(s) or add a small capacitor to the line powering the units.

There is no setting in the GPS to adjust, so you have to swap the unit out with another, fix the circuit or live with it, sorry.
 

Tipracer

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Bajades

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I have both a Lowrance 540c and Lowrance 7200 in the race truck wired to the same power source. The problem is the 540c will turn off when the starter is engaged while the 7200 will remain on. Both units are wired identically and I can find no reason why one turns off and the other doesn't when starting the motor. Is there a setting within the GPS unit menus to fix this or is this how the 540c is supposed to operate? Any help would be great it is starting to get annoying.
The reason that the 540C shuts off and the 7200 does not is because the 540C has a threshold voltage of 10 volts and the 7200 will run on down to 9 volts. During cranking your voltage is momentarily dropping below 10 volts. I have the same combination of GPS units in my Class 1 and they behave the same as your. Our Mezieres starter pulls huge current when first energized and drops the voltage below 10 initially. You can watch this happen by displaying the voltage on the screen of your 7200 and then cranking the engine. If I switch to dual batteries at start up, the problem goes away.
 

Bantle

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Thanks Bajades, when I have both batteries on the problem doesn't occur. I thought that may be the problem just wanted to back up my theory. Thanks a lot guys.
 

Zambo

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We run our GPS and radio off of the #2 battery on a separate buss that bypasses the selector switch, so its always hot. In other words, we run them straight off the battery, bypassing the shutoff switch. We don't have the problem with our gps shutting off but if we did we could crank the motor with the switch in #1, and then put it in both after starting. You have to remember to put it in both or the #2 battery won't charge. Another good thing about this is that we can shut off the power when working on the truck if we have down time but still listen to the radio and keep the gps trip calculations going without worrying that we are going to drain both batteries. We just have to remember to shut off the radio and gps manually when putting the truck to bed.
 

btljuuc

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A rookie here...seem to be learning the hard way. After mounting and wiring my new 540c (class 9 very tight fit), spending more and wiring/mounting the anttena, i'm expirance the same drop in volts (at starting) which makes the unit recycle on...... Does this affect the track log ??. Example: when i prerun and stop in the middle some ware to rest will i loose the track log ? and have to start all over. Befor i try running straight off the batterie any advice would be helpful... only one batterie in the car....
 
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Chris_Wilson

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Yes you can loose your settings and unsaved trails when this happens. Best to run power direct to the battery but keep in mind the unit will draw some power even when it's turned off so you will want to turn off/disconnect your battery when you put the car away. Or put a power switch on the GPS. I think it's actually the antenna power that causes the slow battery drain.
 

RCJoslin

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Stick a Capacitor between batt and gps/radios and it will never happen again.....
 

_

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Stick a Capacitor between batt and gps/radios and it will never happen again.....
To add a little to RCJoslin's recommendation, you should place a 5amp diode (available at Radio Shack) inline from the +12V supply to the GPS and capacitor combination. This will prevent the energy stored in the capacitor from being consumed by the starter and/or other components during start up. In simple terms, a diode is a one way valve. Current will flow through the diode in one direction only. This one way valve will prevent the capacitor from being discharged by any device outside of the GPS system.
 
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