Temperature Guage

[tweetyduck]

I've fitted a new water temp sensor and on a long run on sunday the needle went past vertical on the guage.

I have no fan fitted yet. Just need to fit the relays and X-Eng.

Are there two types of sensor or do you think its just a variation from the old one as this never went past straight up ?

I took out the top brass plug on the block and made sure the water was up to the top. It didn't seem to be. So there might have been a slight air lock up there but until i can get to do another long motorway run i can't diagnose if this was the issue.

The needle went about 15 degrees past vertical but quite a way from red. Earthing the sensor does take it to full red.

Shall i try a jug of boiling water on the sensor. Any other tips to try and find the issue?

I obviously want to be sure it works correctly before i wing my way down south at the end of the month.

[Quagmire]

An infrared thermometer is a great way of checking actual temps if you don't trust your gauge.

[tweetyduck]

Do they read the correct temp on say the outside of the thermostat housing?

I can pick one up for £40 so if its a worth while inverstment i will get one. They seem to be -30 to 300C.

[Quagmire]

My Dad has one and we did pretty much that recently. The temp gauge on his 110 went *phut* and was falsely reading high, he was worried that the gauge was actually telling the truth.

All we did was compare his running temps to mine (both 3.5's) and saw that at various points on the engine they were the about the same.

As for the accuracy, I got a reading of around 80 deg C from my thermostat housing, and on my X-fan switch housing that is located in the top hose. My sump was reading at 90degrees.

From Megajolt I get a reading of 82 degrees most of the time when up to temp so the measurements from the gun would seem to tie in.

With my recently installed TD5 dash this translates to the needle just being to the left of vertical. If you call vertical 12 O'Clock, then I reckon its a about 2mins to 12.

[tweetyduck]

Thanks a million. I'm going to go to Maplins then and get one. It will come in usefull for all sorts of suff.

(If the bloody Gearbox Oil delivery ever turns up !!!! Waiting in all day for an express 24hour delivery, i must be bonkers.)

[pioneer]

Does anyone know how the temperature sensor work's on vehicles?

The way I think they work is as a voltage divider as one side is grounded to chassis and the other goes to the dial.

Something like this

12v---+------------+

| |

RESISTOR |

| |

|------GUAGE-+

|

TEMP SENSOR

|

0v----+

Tom

[pioneer]

Lets try that again

12v---+------------+
     |            |
  RESISTOR        |
     |            |
     |------GUAGE-+
     |
TEMP SENSOR
     |
0v----+

[tweetyduck]

I've fitted the X-Fan and changed back to the old sensor. The needle is back to where to used to be. Been out for a long run and the needle stays put just before 12 oclock position.

I tested the X-Fan with a kettle and the high setting comes on and then stops as the temperature gets low enough. Switch to low setting and its comes back on and then goes off when the water cools. The X-Fan sensor seems spot on when measuring with the IR thermometer.

So my conslusion is the Allmakes sensor is carp.

On a side note the Engine block seems to be at about 92C all the time even when the water isn't at 88C. Seems strange but is an Engine block at 90-95C normal ? (300TDI)