Temperature gauge still not working

Post by **deniro** » 11 Aug 2008, 18:29

Hi All

Following on from my previous technical question my gauge still doesn't work. The advice from AngeloEvs was correct, but (and this is why I'm not a mechanic!) effectively all I did the other other day was to earth the wire against the engine block as per a normal circuit test rather than improving the connection. This meant that it wasn't the sensor I was earthing, just the wires (Hope you understand all that). If nothing else the screw thread should be providing the earth connection. Anyway I need to get the gauge working so here's what I have done and assuming the new sensor works is there anything else that I could try? It is a 1.9 1Y Diesel engine.

1. Checked all connections and wiggled the big white plug in the instrument cluster. All seems ok there.

2. Rubbed the spade connector that attaches to the sensor in the engine against the engine block. This did make the gauge rise (slowly) so I assume this means there are no faults with the wiring or connections between the sensor and the temp gauge.

3. Tried fitting the sensor with and without the washer to see if this helps (it didn't and I have been advised the washer is very conductive)

4. Tried cleaning the housing where the sensor fits to improve connection, this made no difference either.

Apart from all this I can only guess that the new sensor is faulty, but if anyone can think of something else to try before I take the sensor back to the supplier please can you let me know. Thanks.

Post by **AngeloEvs** » 11 Aug 2008, 19:02

If the gauge works when you short the lead to the block then either the sender is wrong or duff or the spade connector isn't in contact with the sender terminal. However, since it worked for a short time I suspect you have poor connection to the sender.

You say that the gauge went to halfway? That is fine if you removed the sender lead from the block but not if you were still holding it against the block. Needle should continue to rise to full reading (not recommended) if you continue to hold the wire against the block.

Put a multimeter, set to ohms, across the sender terminal to the engine block, should read somewhere between 700-1300 ohms for a cool ambient water temperature. That about right for most temp. senders.

Check the condition of the spade connector and the crimped connection for the cable. These corrode and the connection under the crimp deteriorates and can even go open circuit.

If its poor or suspect, cut it back an inch or so and renew it.

Also check that the engine block has 'good' earth to chassis.

See how you get on!

Post by **deniro** » 11 Aug 2008, 19:21

Hi AngeloEvs!

Thanks for the advice. Will try what you say in the morning (my van isn't here with me). The wires into the spade connector do look a bit iffy so I will tidy them up first and see what happens. Also, how do I check the engine block has a good earth? Where should I be looking?

Will let you know how I get on.

Post by **AngeloEvs** » 11 Aug 2008, 20:00

Did you say 'wires' into the terminal? have you got two wires or one into the spade connector? Tha chances of the engine block not having a good conx to earth is slim but some engines rely on a good earth path when 'grounded' components are used. Since you haven't got a meter its a visual inspection for a thickish wire that bolts from engine and connects to body. If you are the least bit unsure, take it back to the mechanic who fitted the sender and ask him to measure from the sender body to chassis earth. Like you say, the washer shouldn't cause the problem since the sender body earths through the thread to engine block.

Post by **deniro** » 11 Aug 2008, 20:09

Sorry, didn't explain it very well. I should have said "strands" not wires (told you I'm not technical!). It is just one wire which is attached to the spade connector!

I'll have a degree in mechanical electrics soon!

Post by **deniro** » 12 Aug 2008, 18:21

Have now replaced the faulty new sensor with a working sensor. Also exposed some nice shiny copper threads on the wire and attached them to a new spade connector. I am now getting a reading but the needle isn't going up as high as it used to (it used to sit about 1/2 way up to the left of the red light and move up and down slightly. So far it has only reached the lower end of the cold area and goes down when I slow down, although it did stay at the "cold" section whilst ticking over. Haven't been able to take it on a long run but did drive about 4-5 miles in total. It usually went to it's "normal" reading after about 3 miles before. It doesn't seem to be a problem, just glad to know it's visible and keeping an eye on the temp! Any ideas why the needle didn't go any higher though?

Post by **AngeloEvs** » 12 Aug 2008, 18:27

Did it ever read normal since you fitted the 1.9Y?

Post by **kimbobill** » 12 Aug 2008, 19:11

Have a look at the thermostat sounds like it's stuck open

Post by **deniro** » 12 Aug 2008, 19:35

The engine was in it when I bought it. The needle has always sat at about halfway between cold and the red coolant light. If I turned on the lights or the fan blower it would go down into the "cool" area, but come back up again when they were turned off. Just got used to it in the end. I haven't checked the thermostat, but it seems ok. The radiator doesn't get hot until a while after the engine has warmed up to normal temperature so I assume this means the thermostat is doing it's job?

Post by **AngeloEvs** » 12 Aug 2008, 19:59

I should give it a good run first, check your coolant level again tho. If the gauge is still low and the engine normal temp then it could be a number of things. My only thought is that you checked the gauge by short circuiting it to earth and that is not the correct way to check it. See how you get on. It could be a number of things, even a mismatched sender unit, poor earth connection from block to chassis, etc.