Ammeter and Temp gauge

[rkohl44]

Hi All,

I've finally worked up the courage to ask (hopefully legitimate!) questions.

Ammeter: On my '82 Catalina 30 the cockpit ammeter gauge never reads anything other than 0. Is this normal? The batteries stay charged on shore power and I haven't had the engine running for more than 3 hours at a time. Should I be worried about the alternator?

Temp: The temperature gauge seldom reads above 120, if it moves at all. I've corrected the loose connection at the sending unit, but it still appears the engine runs really cool, or the gauge is broken. To test the gauge, can I pull off the sending unit and plop it in boiling (or near boiling) water just to see if the sending unit/gauge actually works?

[zellerj]

Great question. In fact my ammeter doesn't move either, and your post reminded me that I had some work to do in the spring.

You can test the temp gauge and the sender by following this procedure:

http://vwts.ru/vw_doc/eva2/GE02/ch3.2.2.html

You can test the ammeter by using a 9 volt battery and an Ohm meter by using this procedure:

https://gasolinegirls.wordpress.com/2014/08/18/how-to-test-ammeter/

[Al Schober]

RK,
Sounds like this is a new boat (to you at least). I'm guessing you haven't gone anywhere with her yet, but would like to? With that assumption:
Ammeter
The ammeter is a tough one. You're going to have to chase some wires and see where they go. Might not even be connected. Some owners install the smart battery monitors and just bypass the original ammeter. Most original ammeter installations were in the alternator lead, hence only read charge current from alternator to battery. There was usually no meter for current being used. Do you have a multimeter? Know how to use it?
Alternator
You need to worry about the alternator if want to use it to charge the batteries. If you never move from the dock, no worry. If you want to go somewhere, you'll need a working alternator. With the engine running, measure the voltage between the alternator case and the terminal with the fat (orange?) wire. 14V or so is a good number.
Engine Temperature
You can test the gauge by removing the wire to the sending unit. With the wire in the air, the gauge will go to one end of the scale. With the wire grounded to the block, the gauge will go to the other end of the scale. Accuracy of the sending unit is another issue - temp senders are pretty reliable. Not like oil pressure senders - always dubious (moving parts). When do you measure 120F - is this still dockside? Try doubling up your aft spring lines and going full throttle in fwd. What does the temp reading go to? Things may be good!

[zellerj]

Another thing to look at is the "trailer plug" connector that is located in the bilge area by the companion way steps. This is notorious in Cat 30s for becoming corroded. Clean up the this plug - for the female end use a piece of emory cloth rolled up tight - and see if the gauges work. You will want to have a clean connector here regardless.

[rkohl44]

Thanks for the speedy replies, zellerj and Al!

Al, yes, you're right. Boat is 14 months new to me and I've yet to go overnight with her. That's the plan, when I'm sure we'll be ok getting back. Yup, I have a multimeter and know how to use it. I'll check the alternator per your instructions and report back.

zellerj: I'll test both gauges, clean up the "trailer plug" and report back.

Thanks again: It'll be a week before I verify the alternator and instruments.

[sastanley]

I would disconnect the shore power for a week and see how things look. If the shore charger is always plugged in and working correctly, the batteries should be at 100% and the ammeter should show close to zero.

My '77 C-30 has no shore power at all. The batteries were always happy to see me when the alternator kicked in and the ammeter would slide to the right, however, after about $100 worth of solar panels and controllers they are always at 100% when I get to the boat.

As we work through the new boat process (we've all been there) some of us C-30 owners might recommend you remove the ammeter circuit as you come to understand the wiring. No rush though.

[tenders]

The way your ammeter works is almost certainly to run all the current produced by the alternator through the gauge itself. This requires a pretty thick wire and the ammeter is, as you've seen, subject to skepticism because if the battery is topped off there shouldn't be much current going through it.

So the question is: what use do you get out of the ammeter? I think the answer is "not enough" and took mine out long ago. A cockpit voltmeter in its place is much more useful. As a sensor it doesn't require a thick wire, and tells you instantly if the battery is discharged (below about 12.5 volts, engine off) and if the alternator is functioning (above 13 volts, engine on).

It is interesting to examine the amps coming out of the batteries and into various loads on the boat, but the cockpit ammeter doesn't measure that. The best way to do that these days is with a sensing ammeter that uses a cylinder "cuff" around one of the wires coming off the battery switch - it measures the electrical field instead of being an actual part of the circuit. But even so you can still get a pretty good idea of the magnitude of the load by watching the cockpit voltmeter. It's easy to see when high drain loads like the refrigerator compressor, halogen spreader lights, VHF high power transmission, or inverter are turned on and off. That might be all you need to know.

This makes me think about the things I have found with benefits that are not worth the associated complexity on boats: alternator ammeters (voltmeter is better), electronic masthead windspeed/direction indicators (Windex is better, specific velocity is never necessary), knotmeters and their associated through hulls (GPS is better), depthsounder through hulls (mount transducer inside of boat), Atomic Four thermostats (plug the bypass and keep the engine cold).

[Whippet]

Solar

Hi Shawn

at risk of distracting this thread - but can you describe your solar set-up for charging. Perhaps it's already in another thread?

after about $100 worth of solar panels and controllers they are always at 100% when I get to the boat.

[sastanley]

Whippet, I don't know if I have mentioned it in detail before..I did update my solar "array" this spring.
I am running a 30 watt panel for the house bank, which is a 230Ah bank, two Gr29 batteries.

I am running a 5 watt panel on the start battery, which is a Gr24.

I chose two separate systems because of the simplicity. Actually, I was given the 5W panel and bought a controller for it. I used to swap the controller wires over to the different banks in between visits. I decided to buy another panel and controller, so now I have two of these $19 charge controllers from Amazon, connected to each panel. http://a.co/e8FdfJx

The 30 watt panel I think I bought off eBay for about $50.

I have very low power consumption, mostly running LED lights, 350mA instruments, and a few water pumps and charging electronics, so this is really just a trickle charger when I am not at the boat, but if I were sailing for a few days, I might mount the 30w panel on the stern rail or something to take advantage of free power. If I remember the math, the 30w panel puts out about ~1.7 amps into the house bank..not much, but plenty over 5 days between weekends. These cheap controllers can handle up to 7amps, so you could get close to 120 watts before you have to think about a more expensive controller. I wired each controller directly to the batteries, again, keeping it simple.

I have a good picture of the 30w panel..the 5w is up on deck under the boom but normally I just set it on the port seat. The boat faces north in this picture, so pretty good south facing in the cockpit..my new slip at the marina is even better, no trees or boat house blocking the afternoon sun like I used to have.

I have a buddy with a refrigerator, and he permanently installed a 100w panel on top of his bimini..it almost keeps up, but now he can sail all day without worrying about draining the batteries when it is hot, and that supplemental charging during the day is enough to keep the batteries for the refer at night too.

[JOHN COOKSON]

Sending Unit ->Wiring ->Temp Gauge

44
Here's a recap of what has been discussed.
Sending unit: The resistance of the sending unit should decrease as the sending unit is heated. Different manufactures will have different specifications for their sending units and gauges. It is important to match the sending unit to their gauge. Some sending units are interchangeable. I don't know which ones those are. If the gauge has alway read low maybe a previous owner installed a non compatible gauge\sending unit. As a guide line the specification for my Teleflex sending unit is 550-750 ohms at 75* and 55 ohms at 212*
Wiring: Disconnect the wire from the sending unit at the gauge and sending unit. Attach a jumper wire to one end and lead the other end of the jumper wire near the other end of the sending unit wiring. Take a resistance reading. should be zero ohms. Any resistance in the wiring will cause the gauge to read incorrectly low.
Gauge: Disconnect the wire from the sending unit at the gauge and power up the gauge. The gauge should peg low. Next short the sending unit terminal to ground; the gauge should peg high. Be careful not to leave the gauge powered up for to long of a time because the coil will be powered up also.

TRUE GRIT

[joe_db]

FYI - The USA standard sending unit for various things is 33-240 ohms. It is possible to find sending units and gauges designed for other ranges. VDO comes to mind, I think a lot of their stuff is 10-180 ohms. There is nothing magical about matching the gauges and senders, the scale and resistance just needs to be the same for each. For one example, if you put a 0-150 PSI gauge on a 0-80 PSI sender, even though the ohm range is 33-240 for both the apparent pressure on the gauge will be about twice what it really is.
Also watch out for dual station senders - they need 2 gauges connected to them to work correctly. The reverse is also true, you can't put 2 gauges on a single station sender

[Al Schober]

RK,
You mention 'cleaning up the trailer plug'. I'd advise against that, and suggest an alternate.
Install a terminal strip, and run the wires to that with crimp ring connectors. I like to apply heat to the ring end and run a little solder into the crimp - the connectors will last a LOT longer. If you prefer the spade connectors (you don't have to remove the screw), be sure to use the ones that have the ends of the spades turned up a bit. The turned up ends keep the connector from falling off if the screw loosens a little.

[rkohl44]

Reporting back:

Left shore power off for a week and checked things out last night.

Battery 1: very weak and could not start engine at all.
Battery 2: strong and started engine with no problem.

While on Battery 2: tested alternator while idling: puts out 10.5v. Revved up to 1/4 throttle and voltage went up to 10.6 or so. Ammeter stayed at 0.

Switched to both batteries, put boat in gear and revved up to about 1/2 throttle. Ammeter "woke up" and went halfway to maximum + reading. Checked alternator again and this time it read 21.75v. (Is this normal?)

So: I'm guessing the alternator and ammeter are working correctly. Right?

Temp gauge: disconnected sender and gauge drops to 0. Grounded sender and gauge jumps to maximum.

So: Temp gauge works. Need to verify sender and wiring to gauge. Gauge finally read 130* after running engine for 30+ minutes. Thermostat "dome" stayed cool to the touch the whole time, even when the engine block was too hot to touch. (Is this normal?) Temp gauge never read over 130*.

[Sam]

For many years I had a rebuilt alternator [actual output max 55 + amps]that produced a similar issue. It was rebuilt by a retired pro who still had his winding equipment and machine shop in his garage and still serviced his harbor friends. The alternator would show "0" or slightly negative after starting and engine idling during warm up. If I "goosed" the throttle a little to rev it up for a second the ammeter/alternator then "woke up" and moved strongly into the positive readings. After a few minutes of running, the deep cycle dual purpose battery would get fully charged and the readings would stay slightly positive. The theory was that it was a quirk in the internal voltage regulator [a sealed plastic electrical component]. Never had a battery problem since I always gave it a quick throttle burst after starting.

About 10 yrs ago I had the A4 under water for a couple of days [ a story for another day] and had the starter and alternator rebuilt again [now up to 63 amps max bench tested]. The amp meter is the same and now goes strongly positive right after starting and settles down to slightly positive. Still no battery problems - one is 10yrs old and the other is 8. My suggestion is to try a brief throttle burst just after starting and watch your ammeter.

[joe_db]

Reporting back:

Left shore power off for a week and checked things out last night.

Battery 1: very weak and could not start engine at all.
Battery 2: strong and started engine with no problem.

While on Battery 2: tested alternator while idling: puts out 10.5v. Revved up to 1/4 throttle and voltage went up to 10.6 or so. Ammeter stayed at 0.

Switched to both batteries, put boat in gear and revved up to about 1/2 throttle. Ammeter "woke up" and went halfway to maximum + reading. Checked alternator again and this time it read 21.75v. (Is this normal?)

So: I'm guessing the alternator and ammeter are working correctly. Right?

Temp gauge: disconnected sender and gauge drops to 0. Grounded sender and gauge jumps to maximum.

So: Temp gauge works. Need to verify sender and wiring to gauge. Gauge finally read 130* after running engine for 30+ minutes. Thermostat "dome" stayed cool to the touch the whole time, even when the engine block was too hot to touch. (Is this normal?) Temp gauge never read over 130*.

NO that is NOT normal and will do a lot of damage