Need help identifying a component that I think is a varistor. It is burnt so it appears black. The circuit is part of a control module for the headlights and keyless entry on a Lincoln. I want to replace the part but can't seem to identify it's value so I can match it up. 
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1\$\begingroup\$ It could also be a thermistor. Can you decode an small diagram on how it is placed on the board? Is it in parallel with an AC source or in series? \$\endgroup\$– user115094Commented Jun 11, 2018 at 15:19
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1\$\begingroup\$ Please add photos of both sides of this part of the board. \$\endgroup\$– user133493Commented Jun 11, 2018 at 15:21
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2\$\begingroup\$ It doesn't look burnt from this angle - seems 'naturally' black. \$\endgroup\$– brhansCommented Jun 11, 2018 at 15:23
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\$\begingroup\$ It got hot enough to melt the plastic case of the module, and burn the trace on back of the circuit board \$\endgroup\$– Mark FarrowCommented Jun 11, 2018 at 15:35
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\$\begingroup\$ Are there any year marks on the PCB? How about some dimensions of the part? \$\endgroup\$– Voltage Spike ♦Commented Jun 11, 2018 at 16:35
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2 Answers
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The color is too even for it to be a result of getting burned. It looks to me like that's its natural gray color.
It could be a MOV (metal oxide varistor), but other component types are possible too. The lead going diagonally across the face makes MOV the most likely.
The bottom line of text indicates it was made by TDK. Look around at likely parts on their web site. If that doesn't work after a reasonable effort, email a picture of the part to their tech support. They should be able to identify it.
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Now that you've shown a picture of the board, we can see that the part designator is MOV1. That removes any doubt about it being a MOV.
answered Jun 11, 2018 at 15:32
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\$\begingroup\$ Yes, I just need a size for replacement. Numbers do not match anything on TDK site and had no reply at all from customer service. \$\endgroup\$ Commented Jun 11, 2018 at 16:56
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It seems to be a MOV. They typically fail short, so probably this blew a fuse if the overheated traces on the PCB are still intact (check them and bypass them if they are damaged).
If you can't find a part number, you can generally replace it fairly safely with one of the same approximate diameter and voltage rating.
But we don't need to do that, because @Andyaka (see comments) has found an apparent TDK/EPCOS substitute B72210S1140K102 which is 13mm diameter and plausibly rated for a 12V automotive environment.
Digikey probably has enough in stock (13,359) to cover your immediate needs, at a very reasonable price.
answered Jun 11, 2018 at 18:02
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\$\begingroup\$ TDK calls these SIOVs. See their Cautions and Warnings. \$\endgroup\$– amICommented Jun 11, 2018 at 19:16
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\$\begingroup\$ @MarkFarrow Andy found the number, and Olin got you to post more photos. I just snuck in and added a bit of general info. \$\endgroup\$ Commented Jun 11, 2018 at 20:51