Gauges dieing
10-28-2002, 08:27 AM
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Gauges dieing
Have had a couple of my Gaffrig (Gaffrig Precision Instruments, which ever "Gaffrig" that is, I can never keep them straight) redline gauges go beserk. The problem is they will itermittently go off scale on the high end and at the same time trigger the low limit red warning light.
The stbd fuel gauge has been doing this for some time, but has been too intermittent to actually test anything. I'd been assuming that it was the fuel sender, but never taken on the task of swapping it out.
Then the port oil pressure gauge started doing the same thing. I was sure it wasn't an actual oil pressure problem as my mechanical gauge on the engine was dead steady (and off scale high and low indicator at the same time is somewhat impossible). The oil gauge was a little more consistent when it whacked out, so I was able to wire it to the stbd gauge (both gauges on the same sender) and verify it was the gauge and not the sender. I replaced the oil gauge and yes, the problem has gone away.
Anyone else having problems with these gauges? I'm wondering if there could be anything in the wiring that is triggering them to fail or just bad luck with them.
Thanks - Greg
The stbd fuel gauge has been doing this for some time, but has been too intermittent to actually test anything. I'd been assuming that it was the fuel sender, but never taken on the task of swapping it out.
Then the port oil pressure gauge started doing the same thing. I was sure it wasn't an actual oil pressure problem as my mechanical gauge on the engine was dead steady (and off scale high and low indicator at the same time is somewhat impossible). The oil gauge was a little more consistent when it whacked out, so I was able to wire it to the stbd gauge (both gauges on the same sender) and verify it was the gauge and not the sender. I replaced the oil gauge and yes, the problem has gone away.
Anyone else having problems with these gauges? I'm wondering if there could be anything in the wiring that is triggering them to fail or just bad luck with them.
Thanks - Greg
10-28-2002, 09:26 AM
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GregP
Had what sounds like the same problem last year. I cleaned all of the connections on the gauges (ground and positive) as well as all of the connections at the junction blocks. This fixed the problem, and infact it also activated some cockpit lights that hadn't worked in a long time. The funny thing was at a glance they hadn't looked that bad prior to cleaning!
Had what sounds like the same problem last year. I cleaned all of the connections on the gauges (ground and positive) as well as all of the connections at the junction blocks. This fixed the problem, and infact it also activated some cockpit lights that hadn't worked in a long time. The funny thing was at a glance they hadn't looked that bad prior to cleaning!
10-28-2002, 09:55 AM
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Tom - I tried cleaning and even replacing the connectors on the fuel gauge when it first started acting up. On the oil gauge I had them on and off a bunch of times while trying to decide if it was a gauge or sender problem and only the port oil gauge ever acted up, and I didn't have a problem when I switched the port wires to the stbd gauge. Guess I could hit them with some contact cleaner as extra assurance though.
-Greg
-Greg
10-29-2002, 12:02 PM
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Check the ground wire on your Starboard motor. Or substitute another ground wire between the battery and the engine. You might also have a bad crimp on the lugs on the wiring. Also make sure you are not using any pipe dope or sealers on your sending units, unless it is the conductive type. (Very rare unless you bought it specifically for an electronics installation.)
Good Luck
Good Luck
11-02-2002, 05:57 PM
#5
Remove the ground from the instrument in question and see the reaction you get.
Pegged out or dropped off then back-track that line of thinking.
Good idea on the engine ground! Most mechanics miss that
Pegged out or dropped off then back-track that line of thinking.
Good idea on the engine ground! Most mechanics miss that
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11-03-2002, 11:20 PM
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11-04-2002, 06:19 AM
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Sorry to take so long to reply, been out testing at work a lot lately.
I'm sure it isn't a ground or other wiring as the first thing I did was check all the leads with the DVM and also ran jumper lines from the ground and sender straight to the gauge as a test.
When I put in the new gauge, (or wired it to the one for the other motor), it all worked fine. I'm sure it's the gauges, just don't know why the early death (only 20-30 hours on them since the new dash install).
An intersesting side note: When I wired the new dash panels I originally tied the port and startboard grounds together. The motors are also grounded to each other. When the problems first started I removed the dash ground tie to see if I had a ground loop problem. It didn't effect things, but I did measure a 5 mv potential difference across the grounds at the dash, while the grounds at the batteries and engines show no cross-voltage. My local avionics guys are always warning about ground loops and saying everything should go back to ground at a single point ... guess they are correct.
-Greg
I'm sure it isn't a ground or other wiring as the first thing I did was check all the leads with the DVM and also ran jumper lines from the ground and sender straight to the gauge as a test.
When I put in the new gauge, (or wired it to the one for the other motor), it all worked fine. I'm sure it's the gauges, just don't know why the early death (only 20-30 hours on them since the new dash install).
An intersesting side note: When I wired the new dash panels I originally tied the port and startboard grounds together. The motors are also grounded to each other. When the problems first started I removed the dash ground tie to see if I had a ground loop problem. It didn't effect things, but I did measure a 5 mv potential difference across the grounds at the dash, while the grounds at the batteries and engines show no cross-voltage. My local avionics guys are always warning about ground loops and saying everything should go back to ground at a single point ... guess they are correct.
-Greg
11-12-2002, 09:59 AM
#10
Be careful using a DVM. They will "LIE" to you.
I used a Fluke 77 for years and if the problem was involved we always went back to the "good old analog"
DVM's are prone to EMF and RF interfearance.
Also reading a DVM in ohms checking for continuity....if there is 1 strand that is touching it will show good. Where if using an analog it puts more voltage through the wire to get it's readings and will be more accurate with respect to integrity of the wire.
Prevents........ good readings in continuity but circuit unable to pass current.
I used a Fluke 77 for years and if the problem was involved we always went back to the "good old analog"
DVM's are prone to EMF and RF interfearance.
Also reading a DVM in ohms checking for continuity....if there is 1 strand that is touching it will show good. Where if using an analog it puts more voltage through the wire to get it's readings and will be more accurate with respect to integrity of the wire.
Prevents........ good readings in continuity but circuit unable to pass current.
