Temp gauge problems

[sapple89]

My VDO water temp gauge is not working properly. The gauge reads about 50 degrees hotter than what it should. I tested the sending unit and it seems to be working fine.

Do gauges need to be calibrated?

Is my gauge bad?

How else can I trouble shoot this problem?

[xb-60]

Is it a bourdon tube (aka 'mechanical') or electrical?

[spdbrake]

Have you removed the sender and jumpered the outer case to engine ground, reconnected the top lead, place the sensor in a pot of boiling water (just left the stove) and turn the key to run? What does the gauge show?

Its usually not a lousy ground or corrosion as those will give you colder readings.

This chart will help on the relationship.
http://www.nsifleet.com/pdf/Temperat...tanceChart.pdf

I use a VDO https://www.vdo-gauges.com/sensors/t...-801-1-16.html

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[spdbrake]

Also I swapped my factory BDR VDO temp gauge (C) to a (F) as the range markings on the (C) gauge were lacking. The needle would seem to stay at the 100C mark. Switching to the (F) gauge I'm at 185F (same as thermostat) and heavy traffic 195F.
If you're running the VDO Vision Chrome gauges a 310-1951 kit will get you the sender and gauge for $60us.
https://www.summitracing.com/tx/parts/vdo-310-1951

This VDO catalog may help as the VDO-US website sucks so bad your ears will pop.
http://www.vdo.net.au/media/189570/2...-catalogue.pdf

[jhv48]

Here’s a thought. Maybe your gauge is working properly and your engine actually is overheating.

[S1965C]

I recently dealt with a similar situation, thinking my thermo fan switch and/or relay was bad (or even the gauge itself). Ended up being the water thermostat was only opening partially.

[cycleguy55]

Originally Posted by sapple89

My VDO water temp gauge is not working properly. The gauge reads about 50 degrees hotter than what it should. I tested the sending unit and it seems to be working fine.

Do gauges need to be calibrated?

Is my gauge bad?

How else can I trouble shoot this problem?

Need more information.

Questions:

1. How do you KNOW the gauge / sender is reading ~50° F high - and not the engine running hotter than you think it should be?
2. What temperatures are you seeing, and what do you think you should be seeing?
3. Where is the sending unit mounted?
4. Mechanical or electrical gauge?
5. If electrical gauge, how have you connected the sender to the gauge? What gauge wire (VDO recommends 16 gauge)?
6. Is your gauge grounded with 14 gauge wire or larger (VDO recommendation)?

VDO instructions here: https://www.vdo-instruments.com/medi...c%20Gauges.pdf