Joined: Nov 20, 2016 Posts: 2 Location: Kaiserslautern/Germany
Posted: Sat Dec 03, 2016 6:34 pm Post subject: Instruments stuck
Since some weeks we got Nekaf M38A1 in our vintage collection. It's running great and condition is very nice but some details need to be fixed:
The instruments are inoperable or moving hard.
Temperatur gauge doesn't move at all but needle moves to max if you hold it upside down. Seems to be broken. Sensor measurements are fine according to temperature.
Oil pressure moves to ~30 psi while running. Measuring the sensor delivers a similar resistance. So it should be fine. Oil pressure is quite low on these engines.
Fuel gauge moves to max if you disconnect and returns to a useful value i'D say. But if you turn off and on again the needles stays way lower. Seems to be a hard moving needle. Ever saw something like that?
The ammeter doesn't move at all. It's a Auto-Lite regulator and the shunt inside the connector seems to be well connected. i measured a 0.006 V difference between the terminals if the headlights are on and 0.000 V if I switch them off. I tested the gauge on bench and it moved with currents like 1 A for maximum deflection. Did anyone got some reference values to measure and compare? Maybe also just something like a hard moving needle?
First make sure you match the sender to the gauge. This varies depending on which specific gauge you are working with. Most gauge changes occurred early on 1951 thru 1952 on the m38 but it was common to see the earlier gauges and senders show up in the M38A1 as well. It helps to check part numbers on the gauges and senders and compare those numbers to the ORD 9 SNL G-758 (M38A1) and if necessary the ORD 9 SNL G-740 (M38). If you don not have these manuals you can download them in PDF format on our downloads page: http://www.willysmjeeps.com/v2/modules.php?name=Downloads
Second, download the TB 9-2300-228-20. It is the troubleshooting guide for the instruments.
It is also very important to insure you have very good grounding of the gauges to the cluster frame and the dash. As the vehicles age and more paint is added to the metals it helps to add bonding jumpers. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Nov 20, 2016 Posts: 2 Location: Kaiserslautern/Germany
Posted: Mon Dec 05, 2016 8:03 pm Post subject:
Thank you for your help. First of all I need to find the part number as there is nothing visibile on top of the sender.
So far I measured the resistance and it reads 0-32 ohms what's matching the values in TB 9-2300-228-20.
The ground connection is somethign I will add for testing soon. With a short jump wire I saw no difference.
According to TB 9-2300-228-20 fuel and oil pressure gauges are fine, the senders also.
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