Weird Electrical Concern

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Weird Electrical Concern

Postby kthurt » Sat Dec 16, 2017 10:51 am

When I turn on navigation lights the following occurs, the volt meter for each engine drops about a volt (from approx 14 volts to 13), the other gauges (both temp and both oil pressure) bump up slightly, ie. temp goes from 165 to 175, all the needles move the same amount. This doesn't happen when I only turn on the anchor light or spot light, so I think it has something to do with the fact the nav light switch also turns on the light bulbs in each of the gauges.
Ken

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Re: Weird Electrical Concern

Postby lg260ss » Sat Dec 16, 2017 12:16 pm

Mine does the same thing and has since new. I've also noticed this on the other boats I've owned. No concern.
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Re: Weird Electrical Concern

Postby gofast24 » Sat Dec 16, 2017 12:19 pm

kthurt wrote:When I turn on navigation lights the following occurs, the volt meter for each engine drops about a volt (from approx 14 volts to 13), the other gauges (both temp and both oil pressure) bump up slightly, ie. temp goes from 165 to 175, all the needles move the same amount. This doesn't happen when I only turn on the anchor light or spot light, so I think it has something to do with the fact the nav light switch also turns on the light bulbs in each of the gauges.


Your oil pressure and engine temperature gauges (and all analog gauges) are just "voltmeters" (even ammeters are just volt meters)! The sending units for both oil PSI and jacket water temp are just variable resistors that change their resistance based on either temp or pressure up/down. Sounds like a half dead battery, corroded battery terminals, or severe corrosion on the connectors at the sending units or the gauges. What happens when you have the engine running? Starting battery voltage readings should go up indicating the alternator is functioning and then what do the other gauges do, Go up or down ?
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Re: Weird Electrical Concern

Postby kthurt » Sat Dec 16, 2017 1:30 pm

gofast24 wrote:
kthurt wrote:When I turn on navigation lights the following occurs, the volt meter for each engine drops about a volt (from approx 14 volts to 13), the other gauges (both temp and both oil pressure) bump up slightly, ie. temp goes from 165 to 175, all the needles move the same amount. This doesn't happen when I only turn on the anchor light or spot light, so I think it has something to do with the fact the nav light switch also turns on the light bulbs in each of the gauges.


Your oil pressure and engine temperature gauges (and all analog gauges) are just "voltmeters" (even ammeters are just volt meters)! The sending units for both oil PSI and jacket water temp are just variable resistors that change their resistance based on either temp or pressure up/down. Sounds like a half dead battery, corroded battery terminals, or severe corrosion on the connectors at the sending units or the gauges. What happens when you have the engine running? Starting battery voltage readings should go up indicating the alternator is functioning and then what do the other gauges do, Go up or down ?


The description of the problem is with engines running. In the off position, the gauges aren't in service. Guess I could try it with ign on but engines off. If it was a battery issue the voltage would drop when I turn on the spotlight. Every gauge moves the same amount, so what are the chances they all have same amount of corrosion. Yes, battery voltage goes up when engines start; hence alternators OK. Next time at the boat, I'll try with ign on, engines off.
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Re: Weird Electrical Concern

Postby Rpontual » Sat Dec 16, 2017 2:26 pm

My guess is that your analogue meters are grounded to the same place. This ground should also the same for the internal lamps.

You could try disconnecting the dash lamps from the navigation lights switch to see if the problem goes away.

If grounding is really the issue, you should fix it as otherwise you cannot trust your gauges.
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Re: Weird Electrical Concern

Postby gofast24 » Sat Dec 23, 2017 1:03 pm

kthurt wrote:When I turn on navigation lights the following occurs, the volt meter for each engine drops about a volt (from approx 14 volts to 13), the other gauges (both temp and both oil pressure) bump up slightly, ie. temp goes from 165 to 175, all the needles move the same amount. This doesn't happen when I only turn on the anchor light or spot light, so I think it has something to do with the fact the nav light switch also turns on the light bulbs in each of the gauges.

Ken, sorry, I should have known that when just turning the ignition on but engines not running you most likely will never have 13+ volts so your indicating 14 / 13 VDC I should have been sharp enough to catch that your engines have to have been running. This is why I like OP's to comment or reply feed back on their problems, we are never too old to learn something :)
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Re: Weird Electrical Concern

Postby gofast24 » Tue Dec 26, 2017 1:03 pm

So, what have you determined so far? If just turning the ignition switch to on (not starting the engines) and after starting the engines the meters reading increase sounds like a bad gauge/sending unit grounds or the alternators are not feeling a high enough field flashing voltage to excite the alternator or extremely low (half dead) battery's ? Rev the engines up a little and back down, what happens after you do that?
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Re: Weird Electrical Concern

Postby kthurt » Tue Dec 26, 2017 5:23 pm

I turned the the ign switchs to on, engines off, then turned nav lights on and voltage meters dropped slightly, similar to engines on. Temp and oil pressure gauges are sitting far left, so their is no movement. Voltage runs higher with engines on, as expected....voltage doesn't drop under other loads.....hence, so don't have a reason to suspect battery or alt problem.
I looked in the Regal manual, it doesn't show a good wiring diagram for the meters. My next step is to remove the dash with meters and observe wiring arrangement and method of grounding (do the meters and light bulbs within the meters have a common ground).
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Re: Weird Electrical Concern

Postby cbsmith » Tue Dec 26, 2017 8:05 pm

I wonder if the lights and the gauges all use the same ground wire and if it has a bad connection. Maybe when the lights are on and drawing a higher load it creates more resistance for the gauges.
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Re: Weird Electrical Concern

Postby Rpontual » Tue Dec 26, 2017 9:44 pm

cbsmith wrote:I wonder if the lights and the gauges all use the same ground wire and if it has a bad connection. Maybe when the lights are on and drawing a higher load it creates more resistance for the gauges.


This is what I said few days ago. The simplest way to troubleshoot this is to disconnect the wire that powers the gauge lights from the switch that is used to power the navigation lights. Perhaps OP already sorted this out...
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Re: Weird Electrical Concern

Postby ImRich » Wed Dec 27, 2017 8:47 am

I took the dash apart on my 2005 boat and found several nuts loose to the electrical connections on the back of a few dash panel meters. A few were so loose, I wondered how they were working at all!

My guess is that they have loosened from years of vibration, or somehow were not tight enough from the factory.

It's easy to check this, simply remove a few dash screws and tilt the dash panel forward. If you move it out of position, place a towel under it to prevent scratches.
Last edited by ImRich on Thu Dec 28, 2017 8:35 am, edited 1 time in total.
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Re: Weird Electrical Concern

Postby gofast24 » Wed Dec 27, 2017 11:44 am

kthurt wrote:I turned the the ign switchs to on, engines off, then turned nav lights on and voltage meters dropped slightly, similar to engines on. Temp and oil pressure gauges are sitting far left, so their is no movement. Voltage runs higher with engines on, as expected....voltage doesn't drop under other loads.....hence, so don't have a reason to suspect battery or alt problem.
I looked in the Regal manual, it doesn't show a good wiring diagram for the meters. My next step is to remove the dash with meters and observe wiring arrangement and method of grounding (do the meters and light bulbs within the meters have a common ground).


When you turn the ignition switch to "on" (engine not running) your gauges should react and give a reading like oil pressure = 0, engine jacket water temperature = 60/70/80F, whatever the engine coolant temperature happens to be when you turn the ignition on, voltage = hopefully some where around 12.6 to 12.9 VDC (unless your house battery charger has been on for hours or days, then possible you would see 13+ VDC just after turning the ignition to on. Remember, some analog gauges have a built in voltage compensation circuit (gauge will read accurately and not dependent on the actual voltage while operating ) and some dont (the readings will depend on the actual voltage feeding the analogue sending units). Remember, all analogue gauges are just voltmeters and the reading correspond to the resistance that the sending units are providing to the gauges. To verify this turn off your house (and most likely starting batteries charger) and ignition switches to off for a couple of hours. then turn on your ignition switches to the on position only, record the readings on the meters. Then, turn on your house battery charger wait 30 minutes or so,then turn your ignition switch back to the "on" position and record the readings on the gauges. Let us know what you see! If your reading are slightly different between a slightly discharged battery and a fully charged (on house battery charger) battery the reason for your difference in gauge reading are just a reaction to the voltage being supplied to them when on battery only and battery with engines running and alternator increasing the voltage while running. Hopefully I did not make this too confusing:)
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Re: Weird Electrical Concern

Postby kthurt » Fri Dec 29, 2017 10:22 pm

We'll, I beleive Romulo was correct....but.... Before pulling out the dash I watched the voltmeter in the cabin as the nav light were turned on...no change in voltage. I opened the dash and found that the wire feeding the bulbs is daisy chained from SB to port and saw a strangely large 10 gauge ground wire coming off the far left gauge which is the port trim indicator. I cleaned up the ground connection on the gauge, I also pulled the spade connection off and on for each bulb and then did the same for a 9 connector plug that handles some of the wiring. I couldn't see other connectors nor where the ground wire goes. Started the engines and turned on nav light. The voltmeters still drop but only slightly, but the other gauges didn't move. But then I noticed that only half the gauges (left side) were wired to that ground, the others had their on ground, a small, probably 16 gauge wire. So, I'm puzzled why the one ground resolve the gauge movement for all the gauges.
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Re: Weird Electrical Concern

Postby gofast24 » Sat Dec 30, 2017 11:13 am

kthurt wrote:We'll, I beleive Romulo was correct....but.... Before pulling out the dash I watched the voltmeter in the cabin as the nav light were turned on...no change in voltage. I opened the dash and found that the wire feeding the bulbs is daisy chained from SB to port and saw a strangely large 10 gauge ground wire coming off the far left gauge which is the port trim indicator. I cleaned up the ground connection on the gauge, I also pulled the spade connection off and on for each bulb and then did the same for a 9 connector plug that handles some of the wiring. I couldn't see other connectors nor where the ground wire goes. Started the engines and turned on nav light. The voltmeters still drop but only slightly, but the other gauges didn't move. But then I noticed that only half the gauges (left side) were wired to that ground, the others had their on ground, a small, probably 16 gauge wire. So, I'm puzzled why the one ground resolve the gauge movement for all the gauges.

The small ground wires on some gauges are most likely just the B- (battery ground) for the gauge lamps. The oil pressure and jacket water temp "analog" gauges should only have have B+ wire going to them coming from the ignition switch "on terminal" and the effective ground terminal will be a wire from the gauge (hopefully marked "sender") going to the oil pressure and jacket water temperature sending units, with their resistance providing the voltage value to the gauges. The body of the sending units (thru the engines ground) are the actual "ground" after going thru the resistance values that the sending units introduce into the "circuit" to provide the readings at the helm. Remember, all the voltage/current that powers everything at the helm is provided by most likely just one high current wire coming from the battery (s) in the engine room so any corrosion, loose terminals, etc. will cause erratic readings at the helm.
Thoughts = Use a accurate digital volt meter, measure the voltage at the battery, access your gauge panel , measure the voltage at the main B+ lead feeding the gauge panel and ignition switch, hopefully it is approximately the same (- 0.1 / 0.3 VDC). Turn your ignition switch to on, re measure the voltage at the panel B+, should have a few tenths of a volt less (due to the battery now powering the gauges, engine ECU, ignition system, etc). Then start the engine(s), and record the readings at the battery and gauge panel main B+ feed terminal. Let us know what you find! Ya, I know , sounds like too much work :)
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