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@Adrian R. posted:

My temperature gauge jumps up and down and on cold start its past the middle on the gauge.  Has anyone had a similar problem and what did you do to fix on the picture here are the only wire that I think might go to the gauge but I'm not sure20210627_135956

Has it always done this or did it just start? Is you car new? Did you recently change any wiring?


Someone smarter than me will no doubt weigh in but off the top of my head I would suspect you either have the wrong sending unit for your gauge or you lost a ground somewhere.

Does your fuel gauge work OK? Idiot lights?

I’ll let a Speedster owner respond to the engine ground. On my Spyder, it goes from one of the starter motor bolts to the chassis tube. On an OEM VW, I think it goes from the starter to the body.

If it’s something it’s always done, as opposed to something that just cropped up, I’d suspect you have a mismatch between gauge and sender. Your pic looks like an OEM VW sender. Do you have the typical Brazilian VDO replica gauges?

If your gas gauge works and the idiot lights work, it’s likely not the ground on the gauge itself.

Last edited by dlearl476

Have you checked your engine ground?  If that’s not it I would suspect you have the wrong sending unit.
Its “normal” for the fuel gauge to bounce around a bit. There’s a fix for it if it bothers you.

I assume you have Chinese knockoffs, even though most Chinese gauges I’ve seen have larger/flatter indicator light lenses.  This is what the Brazilian repros look like  the say VDO (because they are VDO Brazil) they also have pointed pointer centers vs the flat ones like your gauges  

53A3A376-1EC9-48FF-8DAE-10EF4ABBF8D2

Do you know how to check a sending unit for ohm load?

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Ok, so second wire/red light is the oil pressure warning light.

The first(temperature) wire when unplugged, ignition on should peg the gauge at the lower extreme. Plugged in, as the temperature increases, resistance goes down toward zero. It may not reach zero, but it should decrease as the engine warms. If you hook up one lead of an ohmmeter to the sender contact and the other ohmmeter lead to ground this should be easy to track.

250 or 300 degree F VDO gauges have something around 300 ohms at the cooler end, closer to zero at the warm end.

If the gauge is getting good power and ground, like Dave said, unplugging the sender should read cold. Conversely, grounding the sender lead should give you hot temps.

I found some info on TheSamba.

There are two VDO sending units. One with a 244-30 range and one with a 1240-210.

But two things are beyond my pay grade: The gauge not registering any change in temp as the motor heats up, and not topping out or dropping off with the sender unplugged  

I don’t think the wrong sending unit would manifest in either of those scenarios.

Thank you for all the help it ended up being the gauge that's goin bad. Time to try to find a set of gauges any recommendations?  On another note at idle where should the rpms be at.   Mine are around 1500 I had carbs rebuilt with the throttle bodies too so I'm trying to tune it and when I drive I get a bit of pop and studder between 3rd and 4th gear.

@Adrian R. posted:

Thank you for all the help it ended up being the gauge that's goin bad. Time to try to find a set of gauges any recommendations?  On another note at idle where should the rpms be at.   Mine are around 1500 I had carbs rebuilt with the throttle bodies too so I'm trying to tune it and when I drive I get a bit of pop and studder between 3rd and 4th gear.

You might want to call PAS or Hollywood and see if they can simply replace the temp gauge in your combo gauge. They can do it with some. And you end up with a real VDO part in your gauge.



All the builders sell gauge sets, as does Stoddard and Sierra Madre, but that’s an expensive way to solve your problem.

Last edited by dlearl476
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