Re: gas gauge irratic, 37 120

Posted by HH56 On 2012/2/7 23:43:06

According to the eleventh edition of Motors Manual, 35-37 120's use AC gauges. Those are magnetic type and will read full if wire is disconnected. Some of the later cars used King-Seeley which are thermal and those will read empty if disconnected.

While the senders are different in construction, the symptoms sound exactly the same as later ones exhibit when in spots, the resistance winding in the sender has a poor connection with the wiper. On those units the winding is on a strip of phenolic or fiber material which can twist or warp. There could be some oxidation buildup also. An intermittent or poor ground between the sender and tank or body also contribute.

I don't know the resistance range on that particular sender but since it's not the bimetal type, should be able to be checked with an ohmmeter. Would expect a continuous smooth change over the travel. Ones that have had issues seem to jump several numbers high or low before coming back to the proper spot.

EDIT: Since they are supposed to be the same, here is the description out of the 35 120 technical data manual.

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