Coolant Temp False High Reading

[10degnorth]

Hello,

I am chasing down an issue somewhere in my coolant temp gauge system. I have a fresh Subaru EJ22 motor using a stock Vanagon coolant gauge sender through a new sending wire to the gauge. When idling, even before fully warmed up, the gauge reads 1/8 above the LED light. Under load, the needle rises to the highest mark on the gauge then, then upon sitting at a light or a stop sign the needle will fall back down to just above the LED.

At idle.

I have verified that the thermostat is opening and that the engine temp isn't getting above 190 degrees Fahrenheit during normal operation using an IR temp gun on the non-reflective coolant lines.

When I ground the signal wire, the gauge pins high, and when it is disconnected the gauge pins low, as it is supposed to.

The sender I am using is brand new so maybe it was broken off the bat? Alternatively, my gauge cluster is in pretty rough shape so maybe the blue foil is responding weird to the signal.

The weirdest part is that prior to the swap (a month ago) the gauge worked fine, albeit with a different sender.

I am planning to get in there and swap the old sender back in, but its awfully hard to get to with the Small Car Performance coolant manifold.

Has anyone seen readings like this before and found a solution?

Thanks!
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1984 Wolfsburg Vanagon (Daily): https://www.thesamba.com/vw/forum/viewtopic.php?t=773912&highlight=

1988 Microsquirted, Wolfsburg Vanagon (Sold): https://www.thesamba.com/vw/forum/viewtopic.php?t=708000&highlight=

Microsquirt Conversion Guide (Work now Discontinued): https://docs.google.com/document/d/1laXykNPbRYS8MT...2imqd2pnx7

[Pchill2]

Does your fuel gauge work properly?
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87 Syncro Westy
Honda K24 swap

[ZsZ]

There is a topic somewhere about testing the gauge.

The sender show resistance to ground. Soneither the resistance at the sender or the wiring is low or the reference ground is bad.
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Zoltan
1.9 MTdi 2wd Multivan (ex Caravelle)
Van since 2006, engine since 2008

[10degnorth]

[Mckinleyvillian]

Does this van have a coolant temp sender as is located on 1.9? Located on my 1.9 right next to temp sensor II. When that’s not connected, false over heat reading from start up. Make sure it’s connected 😏
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so many roads i know
all i want is one to take me home

85 Vanagon GL 1.9 stick

[MarkWard]

I printed out the table for my manual. I recently verified with resistors the values posted.

https://www.thesamba.com/vw/forum/viewtopic.php?t=465972

[wesitarz]

Your new wire is the same gauge as the old one? I wonder if different resistance with the new wire comes into play.

[10degnorth]