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Old 08-11-2019, 04:20 AM   #1
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Lehman 120 dual station senders and gauges

We took my new 79 CHB out today for her maiden voyage. I have one working oil pressure gauge and one working water temp gauge. Unfortunately one of them is at the lower helm and the other at the upper (a situation perfectly designed by Murphy's Law)

These are the original AC Delco gauges. I don't want to scour around for any used or NOS replacements. The AC senders only work with AC gauges, so adding in a strange gauge isn't supposed to work. (I am told)

I have found some dual station senders available, like from VDO, but I don't find that VDO lists any dual station gauges, at least not by explicit name.

What have others here done? Any and all suggestions, recommendations, and links welcome!
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Old 08-11-2019, 07:07 AM   #2
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Quote:
Originally Posted by CTP View Post
We took my new 79 CHB out today for her maiden voyage. I have one working oil pressure gauge and one working water temp gauge. Unfortunately one of them is at the lower helm and the other at the upper (a situation perfectly designed by Murphy's Law)

These are the original AC Delco gauges. I don't want to scour around for any used or NOS replacements. The AC senders only work with AC gauges, so adding in a strange gauge isn't supposed to work. (I am told)

I have found some dual station senders available, like from VDO, but I don't find that VDO lists any dual station gauges, at least not by explicit name.

What have others here done? Any and all suggestions, recommendations, and links welcome!
No such thing as a dual station gauge. It is the sender that does the work. I have new (three yo) VDO temp gauges with dual station senders. They work just fine but I suggest that with whatever temp gauge you choose that you do some calibration. By that I mean that you use an IR instrument at your engine thermostat and compare that true temp to that shown on your gauges and not the difference so that uou will always know what the actual temp is. These gauges are never precise. Just yesterday while cruising I shot my engines and determined that my gauges read the same, that is, with the correction factor which has remained constant for three years now. My correction factors are +6 on one side and -4 on the other. It's a comfort to know that I can rely on the gauge readouts. However, I still take readings at the engines several times during a cruise. It helps to verify my correction factors.
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Old 08-11-2019, 08:46 AM   #3
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Greetings,
Mr. CTP. Give Lauderdale Speedometer a call. They have been very helpful to me in the past with both parts AND over the phone information.
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Old 08-11-2019, 09:58 AM   #4
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First, determine if it's the gauges or the senders. Switch the good gauge on the bridge with the non-working gauge on the helm. If it works, it's the gauge. If it doesn't work, then check the wiring. Undo all connections, clean them with emery cloth to bright finish. Check continuity with an ohmmeter.

If the helm position is still inop and you are sure the wiring is good, then test the sender. There is a prior thread on the forum. Search "Bad Oil Pressure Gauge" and that will give you detailed test instructions. See also article http://www.tadiesels.com/assets/docs...ance_Value.pdf

Note that US dual station senders are generic. Any 30-240 ohm sender should work with any 30-240 ohm gauge. European 10-180 gauge won't work with US 30-240 sender.
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Old 08-11-2019, 07:43 PM   #5
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@CatalinaJack - Ah, interesting on the gauges. In one place I read that the gauges matter for dual station, and sure enough my AC gauges are factory labeled "Dual Station" so I went along with it. This would explain why VDO sells dual station senders, and oil pressure gauges with no mention of it. Thanks.

@SoWhat - I was assuming gauge and not wiring since the lower helm gauge was sitting at 60PSI with the engine off, and the upper helm at zero. I mucked with the gauge and it dropped to 0. Then I started the engine and it pegged to above 80, whereas the upper helm gauge worked great at every stage. That made me think sender might be okay, upper helm gauge might be okay, and lower helm gauge is busted. I do plan to swap them though, like you say, just to be sure (my day job is as an IT director, so yea, I am an expert troubleshooter :-) ) I've read in a couple of places that AC senders only work with AC gauges - which didn't make sense to me, because like you said resistance ranges are resistance ranges. Hmmmph!

@RT Firefly - thanks for the recommendation! I shall contact them soon with some questions.

I'm thinking that if the wires are good I will try a new oil pressure gauge at the lower helm and see what happens. It's not that awful a job to consider replacing the sender and both gauges if I had to, really.

Thanks again, all!!!
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Old 08-11-2019, 08:47 PM   #6
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After considerable time in the bilge I got my oil pressure gauges both working.It was the sending unit. Still fighting the engine temp gauge issue. On F.L 120's you will find two temp sending units one port one starboard under the expansion tank. The unit on the starboard side is the high temp alarm sending unit, the one on the port side is for both gauges.

I never could totally rely on the engine temp units so I often checked the water discharge and shoot the engines regularly while under way.

I did find that the engine rebuilder had used teflon tape on sending units and I think they were not grounding properly.

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Old 08-12-2019, 08:04 AM   #7
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I have replaced both my temp and oil pressure gages and dual senders with VDO. Purchased from egages.com.
I specifically looked for a temp gage that had a mark at 180 F and found one on that site.
Hope this helps.
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