1999 Skoda Felicia 1.3 base model

 

Hello, for a while now my temp gauge has read 20 degrees low. Engine temp verified at 83 degrees with infra-red thermometer and VC. Both thermistors in sender reading about 330 ohms at that temperature (within 25 ohms of each other). Wiring good from sender to cluster (<1 ohm resistance) and ground good at sender (<1 ohm to battery -). I put a 300 ohm resister across the gauge terminals at the sender and the gauge still read about 65 which is about 20 degrees low according to the resistance chart I found on here somewhere.

 

Fuel gauge and tachometer working perfectly. I fitted a new temp gauge to the cluster but sad to find no change to behavior.

 

Has anyone really dug into one of these? I see a couple of transistors, 4 resistors, 3 diodes and what looks like a single capacitor close to the gauge on the PCB.  Any of these known to cause something like this?  Thinking about just tracing out the circuit and replacing the components, but the car is my daily so it's a bit of a pain.

 

Thanks in advance for any insight!

Edited 8 October, 20241 yr by jbedford
Forgot to say what car

33 minutes ago, jbedford said:

Engine temp verified at 83 degrees with infra-red thermometer and VC. Both thermistors in sender reading about 330 ohms at that temperature (within 25 ohms of each other).

Where were you taking the thermometer reading relative to the location of the thermistors?

1 hour ago, Paws4Thot said:

Where were you taking the thermometer reading relative to the location of the thermistors?

Yep, just under the thermostat housing on the end of the cylinder head.

16 hours ago, jbedford said:

for a while now my temp gauge has read 20 degrees low

 

Mine was going up very fast in the first kilometers and the radiator fan was not working.

 

 

This droved me crazy, one mechanic said that it's the VDO gauge problem and i had to replace it but this was a HUGE task for me plus the expenses.

I have found the cause by my self, the base of the coolant sensor (mine has Blue ring) was dirty (here is an example)

 

 

and this cause alteration of the signal, i clean it thoroughly and everything went back to normal.

On 09/10/2024 at 10:18, D.FYLAKTOS said:

 

Mine was going up very fast in the first kilometers and the radiator fan was not working.

 

 

This droved me crazy, one mechanic said that it's the VDO gauge problem and i had to replace it but this was a HUGE task for me plus the expenses.

I have found the cause by my self, the base of the coolant sensor (mine has Blue ring) was dirty (here is an example)

 

 

and this cause alteration of the signal, i clean it thoroughly and everything went back to normal.

Thanks very much for the info. Does your car have air conditioning? Trying to figure out why your have the blue sensor and mine has yellow. Thanks!

Yes it has.

I bought it with blue, i have tested in the past 2 sensors with yellow ring and both times i had major problems.

I removed them, replace with blue and everything OK.

Don't buy cheap sensor as VIKA or "no name", buy a brand one, "well know name" in the market.

On 11/10/2024 at 15:43, jbedford said:

Thanks very much for the info. Does your car have air conditioning? Trying to figure out why your have the blue sensor and mine has yellow. Thanks!

Many vehicles with Alex AC have the yellow ring, don't stress about it, they only thing you should care about is the actual sensor having a very true to-factory temp curve.
And very few aftermarket ones do

Just wanted to confirm that the blue sensor works properly on my 1999 1.3. I used febi bilstein.

12 hours ago, jbedford said:

Just wanted to confirm that the blue sensor works properly on my 1999 1.3. I used febi bilstein.

 

I have 3 coolant sensors with yellow ring, the 2 tested in the road and proved ****, with both of them i had higher coolant temperatures.

Here is the 3rd, take a look, no marks on it, would you trust this garbage?

 

 

 

Install a Blue with indications-part code on it and you will be fine.