MEP 803a Water temp gauge

cdgrogan

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Hello everyone and thank you for all the useful info. I've been lurking for many years and finally picked up a MEP-803a. Everything seems to be working properly except the water temp guage. When the unit is running and up to temp, I checked the supply voltage to the gauge which was 26v and from the sender I was getting 12.6v to the gauge but the needle on the gauge did not budge from the far left. I think I was originally getting 6v when the unit was cold but will have to double check that. My question is, did I miss something or is the gauge bad? Thanks in advance.
 

Zed254

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Check wire connections from sender. Also, make sure gauge is not 'too tight' in the panel. I've read that if you tighten them too much they can hang up....connection screws, mounting bracket, all of them: snug, not tight. I believe the gauge measures resistance of the sender. Ohms. Attached chart shows temperature vs ohms for testing. If your gauge is shot, some possible replacements.

My notes regarding Temp Gauges: Beede (PoS) Temperature Gauge: NSN 6685-01-369-6549, Beede number 945329. 24 volt, 100 – 240
Water Temp Gauge: VDO 310-907 ,
ISSPRO R8750, VDO A2C60000963
 

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cdgrogan

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Zed thank you for the print out for the gauge. I jumped from the sender to the ground on the gauge and it pinned to the right like it was suppoased to. I then checked the resistance from the sender wire to the ground on the gauge and was getting OL. So I then ohmed the actual sender which also said OL on my tester. Guyfang I also checked the wiring. The line voltage (26 volts when running) was on the ignition side of the gauge, the two ground wires were on the ground side of the gauge and the line from the sender was on the sender side of the gauge. Loosened all and then snugged them down but not to tight.
So it looks like the sender is bad since it is reading OL. Thanks everyone. Does anyone know where to get one or an equivalent?

 

Zed254

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You will need the various TMs available for your machine. While searching for the NSN of the sender I found a testing procedure in TM 9-6115-642-24:

2-92 COOLANT TEMPERATURE SENDER.
NOTE
Engine must be cool when performing this test
2-92.1 Testing.
a Shut down generator set
b. Open left side engine access door
c. Disconnect and tag electrical lead from coolant temperature sender (4, FIGURE 2-25)
d. Set multimeter for ohms and connect to coolant temperature sender terminal and casing. Multimeter indication
should be greater than 300 ohms.
e. Start generator set and observe multimeter.
f As engine operates and coolant temperature rises, multimeter indication should decrease,
g. Shut down generator set.
h Replace coolant temperature sender if indications are other than above
i. Connect electrical lead, remove tag, and dose left side engine access door.

TMs here: https://www.steelsoldiers.com/showt...-802-5KW-Generator-and-MEP-803-10KW-Generator

And a search on SS for '803 coolant sender' gets many hits like this one: https://www.steelsoldiers.com/showthread.php?182571-mep-803a-coolant-temperature-sender
 
Last edited:

cdgrogan

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Also what is the difference between the engine temperature switch and the thermostatic switch? I was looking on the TM (http://www.liberatedmanuals.com/TM-9-6115-641-24P.pdf) and now I am confused. One has one wire going to it and the other has two going to it. I'm hoping the one that has two wires going to it is the sender because if its the other then I tested it all wrong.

8 PAOZZ PAOZZ 06555 127338 .SWITCH ENGINE TEMPE 1
9 PAOZZ PAOZZ 30554 88-22203 .SWITCH THERMOSTATIC
 

cdgrogan

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Thanks everyone for the help. So I ohmed it out and was getting OL and kept thinking the sender is shot. Then I moved to a different ground and started to get a reading. After some finagling I was getting a reading of 120 ohms and with a temp gun it showed the temp of the water housing at 140. So I went back to the gauge that I previously confirmed was working by using a jumper and still nothing, all the way left. I then loosened all the connections of the back of the gauge to see if maybe the were to tight and after I put it back together it started reading again. Not sure exactly what I did but it is working. Maybe the gauge was too tight or there just wasn’t a good connection somewhere. Either way it’s working for now. Again thanks everyone for all the help and links. This is an impressive unit and looking forward to learning more about it.
 

Zed254

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Cool. Now you have time to research the various manufacturers of these gauges and find a more reliable one. I searched on gauge temperature range (100 - 240F), ohm range, and 24 volts.
 

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Ray70

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I've used a few of the Faria Euro Black gages, but some of the readily available , cheap ones need an $11 voltage adapter board , or just wire in a 100 ohm resistor ( in the case of the oil gage) into the +24 to drop it to 12V. Might be worth the extra money to just get gages designed for 24V right off the bat next time...
 

Light in the Dark

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Cool. Now you have time to research the various manufacturers of these gauges and find a more reliable one. I searched on gauge temperature range (100 - 240F), ohm range, and 24 volts.
Those looks pretty nice... manufacturer info? Work with the stock sender or need a new one? Got an 803 out the door that I had to replace on.
 

Light in the Dark

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Oh and almost as important... are the rear terminals the same layout and style as the milspec gauge?
 

Zed254

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My Coolant gauge is Teleflex, the Fuel and Oil are both Datcon: I don't really care for the Beede gauges. For coolant I learned to searched for temp reading (100-240): and now I've got a couple extra 280F gauges on the shelf. Look for 24 volt and the lower 'American' sender. Europe has a different sender ohm reading. You are looking for 30 to 450 ohms according to that Beede chart. Note that with these gauges a separate light 'kit' is needed - bulb and fixture to hold it.
 

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