Instrument issue / Chartplotter / GPS Fix

[Fred Aloha]

I have a raymarine A75 chartplotter.
Every time I start the engine (last year only, before, it was okay), the GPS restart but lost satellite Fix.
It takes about 1 to a few minutes to show position on the maps again. This is not very handy.
I wonder if there is an internal battery that needs to be changed?


If there is nothing we can do, I will probably isolate GPS on Bank no2 batteries or use a diode and a condenser.

Since the cable is on the boat an hour drive under a tarp, do someone have the power pinout to do some testing?

Thanks

 

[dlochner]

How old are the batteries? It sounds like the current draw from the starter drops the voltage below a threshold which causes the CP to lose its GPS fix. When the batteries were newer, this didn't happen.

Isolating the starting circuit from the house circuit would be a better path to follow. Replacing the batteries will also work.

 

[Ward H]

Isolating the starting circuit from the house circuit would be a better path to follow.

My new Axiom CP and i70 displays would restart when I started the engine. New wiring and batteries did not fix the issue.
I installed a Dual Circuit Plus battery switch to isolate the house bank from the start bank. No more drop outs.

 

[Fred Aloha]

Anyone has the pinout of the top picture?

Pin 1 =
Pin 2 =
Pin 3 =

I would like to do some test but I don't want to reverse polarity.
Cable or unit would be great (my cable is in the boat 1 hour drive under a tarp full of snow...)

Thanks

 

[dlochner]

What test do you want to do, resistance or voltage?

To check the voltage, disconnect the power cable from the unit, turn the power on, and measure the voltage across the pins. On 2 pins you will probably find voltage. Not sure about the 3rd pin. When measuring voltage there is no need to worry about polarity, if you get it backwards the voltage will read as a negative number, if it does, just reverse the leads.

Voltage measurement is passive, i.e., the meter simply reads the voltage across the pins and does not add any of its own power. Measuring resistance is active, the meter will apply a current across the circuit to measure the resistance, it is then possible to reverse the polarity. In some circuits this can be an issue in other circuits it doesn't matter.

 

[Fred Aloha]

Thanks for the explanation dlochner

If I would have acces to the boat and cable, it would be graet.
The problem is: "(my cable is in the boat 1 hour drive under a tarp full of snow...)"

 

[Hydro Therapy]

I have that same issue with my gps. I just assumed it was a ground issue. I never attempted to fix it. Mainly because I’m ignorant when it comes to electrical stuff.

 

[dlochner]

I don't think the problem is with the Chartplotter, it is probably a problem with the power supply. When the engine is started the voltage drop causes the CP to power off and then come back on. After dropping the GPS connection it takes a few minutes to find the satellites again. The solution is to provide a more stable power supply, by separating the house and start batteries and preventing the voltage drop on the house bank.

If you want to power up the CP at home, you'll need a 12v power supple and a power cable. With those you could simulate a start by powering up the CP, then turning the power supply off and on quickly. My guess is you will have the same problem with dropped gps connections.

What kind of tests were you planning to do?

 

[LloydB]

From : Raymarine a75 Installation And Operation Instructions Manual (464 pages)
1. Vessel power supply positive (+)
2. Vessel power supply negative (-)
3. In-line fuse (If your products power cable does
not have a built in fuse then an in-line fuse
should be fitted.)
4. Drain wire connected to vessel negative power
supply.
5. Product power cable
6. Vessel battery
I never have touched one of these but if I was going to check it I'd turn off the power then test the three pins against each other for 12 volts DC. find which two pins are shorted together while using the ohmmeter then turn the power back on and find which pin is 12 volts DC with the Volt meter. Watch the 12 volts remaining turned on while starting the engine if it goes off you will have a clue.

 

[Fred Aloha]

Went for the first bike ride of the season to look at connector polarity

 

[JohnShannon]

Well my last boat had Raymarine stuff and I thought it was absurdly susceptible to voltage dips. The GPS hardware is likely running on 3.3V or even lower. No reason at all that this can't be kept alive through a cold crank. Does you cars nav forget where it is when you start the motor? Fresh battery thicker shorter wiring clean connections all that stuff.