Non working temperature gauge

[jswagger]

For the last three years I have had a non-working temperature gauge and analogue clock in my 1987 1.9 petrol (low coolant led flasher, fuel gauge and all warning lights are working though). I replaced the gauge and clock with new ones and have exactly the same problem as before! Of course the replacements might be knackered but having exactly the same problems was a bit too much of a coincidence I thought.

I have done a search on the forum and have removed the plug from the temperature sender unit and connected a wire across the plug but the gauge does not move with the ignition on or off. As the clock and gauge don't work would this point to a power fault with the PCB? If so why does the fuel gauge work as does it not get power from the same PCB? The needle on the temperature gauge is not visible (it's completely over to the left) and from reading other posts this perhaps would point to no power getting to the gauge. If so how do I check this?

Any help or pointers gratefully received as I hope to get this fixed before 4 years is up!!!

Thanks

[Fritz]

I'd be having a tendancy to be checking for broken wiring (continuity check) in the engine bay....

Regards


Fritz,,,,,,,,,,,

[jswagger]

Thanks for the reply.

Would the clock not working be an engine bay wiring problem too?

Is there any way I can check power is getting to the pins (on the multiplug that plugs into the PCB)? If so which pins?


Thanks again.

[Grun]

Thanks for the reply.

Would the clock not working be an engine bay wiring problem too?

Is there any way I can check power is getting to the pins (on the multiplug that plugs into the PCB)? If so which pins?


Thanks again.

Clock positive is pin 5 and supply is through fuse 3 (which also feeds the courtesy {door} lights)
Clock earth is pin 3 (which is also earth for instrument lights etc. etc.)

Have a look at this..https://club8090.co.uk/forum/viewtopic.p ... 34..thread" onclick="window.open(this.href);return false; for more temperature gauge info. Big thank you to AngeloEvs for his super diagram.

Mike

[AngeloEvs]

Good news first, clock wiring not in the engine bay. Like Grun suggests, check fuse for clock. If OK then I would remove the instrument pod and simply test the clock on a bench by hitching voltage across the terminals of the clock itself. If it works then check the PCB pins 5 and 3 actually connect to the clock terminals - mines knacked but thats OK as I don't like being reminded of time passing by anyway.

As for the temp gauge, don't rely on short circuiting the terminals as the fault may be in the earth path which terminates under the ignition coil having meandered through two connections in the junction box in the engine bay. Somewhere down the forum list is another post with a duff temp gauge and that might help. You can measure the resistance of the coolant sender to check if its ok, readings will vary but approx.........

Cold = > 1k Hot = 100 ohms or thereabouts but you wouldn't want to get under a hot engine so check it from the junction box.

inset shows location of T7 Junction box.

pins show conx to test sender resistance.

[jswagger]

Thanks for the replies.

Sorry for the dumb question but where can I hook up 12v on the back of the gauage/clock to test if it is working?

[AngeloEvs]

I hang the edge connector over a table as it is fragile. The nut at Arrow B provides a good point for the earth connection.

To test the gauge connect 12 v to pin 8 and short circuit C to B ( only for a few seconds tho - until the needle just starts to move, I use 100 ohm resistor across C - B).

To test the clock connect the 12V supply to pin 5 or to the clock itself.

Hope this helps....all the best (E D I T getting late and originally said pin 7....sorry!)

[jswagger]

Thanks for all your replies. I have been away but have had a chance now to check the gauges.

Both the original and replacement temperature gauges work when shorting out the screws B & C in the photo kindly posted by AngeloEvs. As they are not the problem I have checked the wiring. There is continuity between the brown wire (earth?) of the plug on the temp sender to the pin marked B on the photo. If I am correct this means that earth circuit is fine? I have also done a continuity test from the yellow & red wire on the temp sender plug to pin 8 on the multi plug that plugs into the instrument panel PCB. This test failed (no beep) so there must be a break in the wiring somewhere? Any ideas where?

Out of interest the yellow & red wire in the instrument panel multi plug does not go to pin 8, is this correct? I thought the wiring would be the same colour throughout.

As for the clocks I cannot get either working! I connected 12v directly to the clocks by connecting -ve to the screw (by the 10V out arrow in the photo posted ) and the +ve by removing the white plastic sheath that connects to the track that goes to pin 5). Is this the correct place to test?

Thanks again for all your help, I am even more determined to get this sorted now.

[Grun]

jswagger,

If you re-read AngeloEvs' post..............

To test the gauge connect 12 v to pin 8 and short circuit C to B ( only for a few seconds tho - until the needle just starts to move, I use 100 ohm resistor across C - B).

My italics.

The yellow and red wire from the temperature sender goes to pin 6.

To check the clock pin 5 should be +12volts and pin 3 (or the other terminal of the clock) battery negative/chassis/ground.

I am working just from the Haynes diagram, my instrument pod is fitted, (and...... fingers crossed....working)

Hope this helps, at least 'till AngeloEvs gets back to you.
Mike

[clartsonly]

this might seem obvious, but you are sure you have removed the socket from the right plug, I spent two years trying to get my temperature gauge working and I was constantly testing the wrong plug in the thermostat housing, it is the one you cannot access from the engine bay, not the one on the left hand side of the thermostat housing, that sensor is for the carb heaters relay.

[jswagger]

this might seem obvious, but you are sure you have removed the socket from the right plug, I spent two years trying to get my temperature gauge working and I was constantly testing the wrong plug in the thermostat housing, it is the one you cannot access from the engine bay, not the one on the left hand side of the thermostat housing, that sensor is for the carb heaters relay.

Actually in the first place I did test the wrong plug but when I did a search on the forum I read one of your (I think) threads where someone pointed out the corrrect plug for the temp sender was the accessed under the van.

[jswagger]

jswagger,

If you re-read AngeloEvs' post..............

To test the gauge connect 12 v to pin 8 and short circuit C to B ( only for a few seconds tho - until the needle just starts to move, I use 100 ohm resistor across C - B).

My italics.

The yellow and red wire from the temperature sender goes to pin 6.

To check the clock pin 5 should be +12volts and pin 3 (or the other terminal of the clock) battery negative/chassis/ground.

I am working just from the Haynes diagram, my instrument pod is fitted, (and...... fingers crossed....working)

Hope this helps, at least 'till AngeloEvs gets back to you.
Mike

Thanks for the help. Do you mean if I am testing for continuity between the live terminal of the sender and the PCB I should test between the sender and pin 6 instead of 8?

Thanks to your advice about the correct pins for powering the clock I have now managed to get one of the clocks working!

So now I have two working temp gauges and one working clock I have one complete set of working instruments (they work on the bench), working except for when they are plugged into the vans multiplug. This makes me think the fault may be in a common wire that both use, any one any pointers? If it was a faulty earth for the PCB then why does the fuel gauge work?

Thanks again, I'm getting closer.

[Grun]

jswagger,

Thanks for the help. Do you mean if I am testing for continuity between the live terminal of the sender and the PCB I should test between the sender and pin 6 instead of 8?

Yes there should be continuity from the live (Yellow/Red wire) side of the 'sender' and pin 6 of the connector to the PCB, and to the appropriate track of the PCB when it is in contact with the connector.

Looking at wiring diagram for the next question you asked.

Mike

[Grun]

jswagger,

So now I have two working temp gauges and one working clock I have one complete set of working instruments (they work on the bench), working except for when they are plugged into the vans multiplug. This makes me think the fault may be in a common wire that both use, any one any pointers? If it was a faulty earth for the PCB then why does the fuel gauge work?

It looks to me as if without the main earth from the PCB through pin3 of the connector you would not have a working clock, rev counter (if fitted) dash (instrument) lights, high beam light, etc. (It does look as if the fuel gauge might still get a supply through it though), and the indicator tell tale light would still work.
It is more likely that you have more than one poor connection between the PCB and connector. Someone recommended gently reshaping the contacts in the connector, (and cleaning the PCB tracks to get good contact).
Are you using a multimeter to fault find?
Mike

[jswagger]

It looks to me as if without the main earth from the PCB through pin3 of the connector you would not have a working clock, rev counter (if fitted) dash (instrument) lights, high beam light, etc. (It does look as if the fuel gauge might still get a supply through it though), and the indicator tell tale light would still work.
It is more likely that you have more than one poor connection between the PCB and connector. Someone recommended gently reshaping the contacts in the connector, (and cleaning the PCB tracks to get good contact).
Are you using a multimeter to fault find?
Mike

All instrument lights (inlcuding full beam & indicators), warning lights (including low coolant) and fuel gauge have always worked, it's only the clock and temp gauge that haven't. I'll try gently fiddling with the multi plug connector. Yes I am using a multi meter to fault find, are there other tests I can do?

In repsonse to your other kind post I'll do a continuity test between the temp sender and pin 6 when my assistant is next around.

Thanks again.