Gauge or Sender?

[egaito]

Stb Temp gauge is acting up. If I turn the key and leave it on, or start the motors, it creeps up quickly to nearly the full range of the gauge.

If I disconnect the wire at the sender, the gauge drops to 0. Put the wire back on and it starts climbing again.

I'm guessing sender....but hoping for some insight to back that up.

If I put a meter in-line from the sender to the sender wire, what should I looking at? Resistance, voltage, or current?

Thanks,

 

[MikeP]

This might be helpful:

http://www.gaugeguys.com/trouble.htm

 

[egaito]

This might be helpful:

http://www.gaugeguys.com/trouble.htm

Unfortunately, it doesn't fit any of the models described there.

If the gauges are resistive, they should "snap" to position when the key is on, but they don't. If it's electric, and the wire removed, it should read hot, but does not.

If there were a stray ground in the sending wire, the gauge should still read something when disconnected from the sending unit, but it goes to 0.

If I can figure out if they're voltage or resistive based, I should be able to tell with a meter whether the value on the sender is changing the gauge, or if the gauge itself is hyper-reacting to little or no signal.

Are these senders DD parts, or can they be had elsewhere in a more generic form?

Thanks,

 

[Pascal]

check that the instrument gauge light is off... I replaced the bulbs on mine (flybridge) and for some reason it caused the gauge to heat up and creep up!

might have been the wrong bulb, not sure.

 

[egaito]

New Clue:

Both the lower and upper helm gauges behave the same.....points to sender, BUT:

This sending unit has one wire on it. How does it get repeated to the upper helm?

 

[MikeP]

All electrical engine gauges are the same - regardless of the vehicle they are on - it's a generic trouble shooting guide because it works with virtually any gauge except mechanical. If you follow the troubleshooting you should find the problem

 

[egaito]

All electrical engine gauges are the same - regardless of the vehicle they are on - it's a generic trouble shooting guide because it works with virtually any gauge except mechanical. If you follow the troubleshooting you should find the problem

Yea, well I tried chastizing her for not behaving like the the generic guide says she should, but that didn't work either. Go figure.

 

[egaito]

check that the instrument gauge light is off... I replaced the bulbs on mine (flybridge) and for some reason it caused the gauge to heat up and creep up!

might have been the wrong bulb, not sure.

Now that's a creative solution!

Since it's on both levels, I had Ang turn off the Fry-Daddy, even though it wasn't in the troubleshooting guide, but apparently it's not the residual heat from our fries as that didn't fix it either.....

If I'm looking at the right sender, I think I've identified the problem. What I'm trying to confirm now is whether or not that is the right sender.

Yes, if I disconnect it, the gauge reads 0....BUT shouldn't the helm gauges be on a 2-wire sender, one for each level, or is the single wire sender somehow repeated to the upper helm?

Do the upper and lower alarm panels each have a sender input? If so, perhaps this is where the double-wire sender is connected.

The engine room gauges work off of a pyrometer cable to an easily identifiable sender, so at least that's eliminated for the equation.

 

[Beckytek]

The sender on my boat (gas) has only one terminal on the sender. I don't see why it would be any different for diesel. The senders are graduated for one or two guages. The only difference is the resistance of the sender. The wire goes from sender to one guage S terminal then continues on to the second guage S terminal. If the guage is slow to react I would check all three terminals at the back of the 2 guages. It sounds like a bad connection.
The sender also has to have a good connection to the block, no teflon tape here. Ron

 

[Brian Degulis]

You should have one sender (single wire) controling both gauges. Take the wire off the sender the gauge should read near 0 then touch the sender wire to ground the gauge should read Max. If this is what you get then the sender is bad.

Brian

 

[Maynard Rupp]

All sender wires on our boat go to the flybridge terminal strip. The gage wires go from that terminal strip to each gage, one on the bridge and one at the lower helm. That may be because our lower helm is optional. Regardless, all senders are a single wire and go to a terminal strip where it splits to both helm areas. If neither gage works on a particular side, it could be the sender or coroded lugs on the wire at the sender or any of the terminals or at the gage. We had a situation where both P & S lower helm temp gages were inop. I checked everything and finally bought 2 new NOS gages from Sam's. That was the problem, both of my AC temp gages were bad.

 

[REBrueckner]

Am I correct that a sender is designated either for a single gauge or twin gauges? In other words, one gauge model is matched to a single output and another model for twin outputs? Or to say the same thing differently, a twin gauge sender doesn't work properly with a single gauge output.

 

[Beckytek]

Yes, you must specify if you have one or two guages as to what sender to buy. If you get the wrong one the temperature reading will be inaccurate. Ron

 

[TedZ]

The senders for two stations may have one wire BUT they are a different sender for driving one gauge than when driving two because the resistance in the gauges end up being in series with the sender's resistance. I.e. sender to one gauge, that gauge to the next gauge.

Back to the basics. The one wire senders have a grounded case. They will have instructions that say something like "Do not use teflon tape or thread sealant on the sender." The creeping of the gauge could be a bad sender but is likely a bad ground. Remember, hot goes to the gauge and the sender closes the circuit to ground though the senders varying resistance. Clean the threads.

Two wire senders, which i prefer, have one of the wires going to a GOOD ground...the other to the gauge.

Hope this helps.

Ted

 

[egaito]

Well, based on the last round of suggestions, the sender is the likely culprit.

I did clean the threads and connections, and try grounding to the block, which as expected, pegged the gauge.

So I take it this is a DD part then?

I don't want to take this one out to bring in for a match, and lose the coolant mix. Anyone happen to have a part number for a 1980 with 8v92s or tips for getting the right replacement?

Thanks for all the suggestions,

 

[captddis]

It is a AC sender. They are NLA. With some effort you may find a NOS sender or a used sender. The temp senders on the AC gauges are all the same the gauges are speced for single or dual. If you can't find one I will look.

 

[Maynard Rupp]

Check with Sam's. They have most of those parts and senders.