Coolant Red Flashing Light

[pfield69]

That looks nothing like mine. How do you post pictures, I keep getting oversized warning and its only small

[MidLifeCrisis]

You can't download a pic direct to this forum, you have to download it to a third party 'image website' then link to that in your replay..... This is how I do it (using a site called 'Imgur.com';

• Go to http://www.imgur.com
  In the top right of the page, under 'Upload Images', click on 'Computer'
  In the window that opens navigate to your picture file and select it by clicking 'Open'
  In the next window that opens click 'Start Upload'
  A new window will open showing your pic.
  You can now copy the correct code to paste into your reply (use the one called 'BBCode')
  Copy the BBCode and paste it into the reply window in the club8090 forum.
  If the forum complains that the pic is too big you can also select other sizes of pic on the imgur website by clicking on the options to the right of 'Sizes' on the right of this page on the imgur website where you pic is displayed.

Hope that helps.

[pfield69]

deleted for bad picture code

[pfield69]

That was harder then I needed to be, thanks Flickr!!

The other sensor is just around the corner to the red one you can see on housing.

In addition to this I have completely taken the dash apart, checked it, removed some broken plastic bits (and mad some more).

Now we have a different scenario.

Ignition turned on red light flashes, then goes out for 5 seconds, then starts to flash again.
Removing relay #45 now stops the light from flashing.
Temperature gauge now working - I didn't leave it long enough to see where it settled but looked a little higher then normal i.e. just above the solid white line.

[MidLifeCrisis]

Now we have a different scenario.

Ignition turned on red light flashes, then goes out for 5 seconds, then starts to flash again.
Removing relay #45 now stops the light from flashing.
Temperature gauge now working - I didn't leave it long enough to see where it settled but looked a little higher then normal i.e. just above the solid white line.

OK - so if removing relay 42/43 (not 45?) stops the light flashing then the problem is either with the relay itself or more likely the coolant level probe.
With the ignition turned off, stick the relay back in and remove the connector from the coolant level probe: Now turn the ignition on - does the led continue flashing after the initial flash;

• If it doesn't then the probe is at fault (or you have low coolant levels).
  If it does keep flashing then the problem is probably with the relay (or less likely the wiring to the relay from the level sensor).
  

[pfield69]

I'll try that tomorrow.

Is there a way to test the relay? If it is the relay where can you get it from?

I'm guessing there was a problem with the flexi-circuit too as after removing gauge it now works.

[pfield69]

ok, jumped out coolant level sensor, still the same ie 5 sec flashing, 5 seconds not flashing, then flashing.

[MattBW]

I've been reading this with interest, its a job I need to do on mine and this is incredibly valuable.

I've just had my engine bay rewired (it was pretty shocking). My fuel gauge hasnt worked as long as I've had the van (sender perhaps) but the temp gauge always did albeit it it never got very high. I have a new voltage regulator to replace as first job.

However ever since the rewire, the needle goes all the way upto hot (even when cold) red light flashes up until i start the engine when it goes town to zero and the light goes out. As it didn't do this before I am a little baffled.

[MidLifeCrisis]

ok, jumped out coolant level sensor, still the same ie 5 sec flashing, 5 seconds not flashing, then flashing.

When you say 'jumped out' coolant sensor - what exactly do you mean? You should be just unplugging it (not doing anything else - jumping usually suggests that you are attaching a wire across the terminals?)

Its not easy to test the relay (but it can be done if you take the relay out, have a 12v source, some wire, a bunch of resistors, a bulb/led etc etc). Lets eliminate everything else first ....

[MidLifeCrisis]

FYI - here's a section of an old thread where I tested my relay ..... might be useful if you want to give that a go.

OK - I yanked the module (43) out of the van today to have a play;
I set up this circuit on the bench;



With the switch set as it is in the pic, the light is out (the 27K resistor simulates the coolant probe being dipped in coolant)
- So that is correct operation.

With the switch pushed (i.e. simulate the coolant probe not being in the coolant), light goes ON after about 5 secs
- So that is correct operation too.

Set the switch back to how it is in the pic, and the light goes OUT again (it takes about 30 secs to go out)

So from the experiment it would seem that for my '43 Module' the warning light would be able to go out once it had been set.

Also, I'm surprised how long it took for the light to go out again (i.e 30 secs) ..... I tried a 150K resistor on that switch (in place of the 27K one and it took over 2 minutes to go out! So, if the resistance of coolant is very high (which I assume it is) then its possible that no one has waited long enough to see the light go back on again?!?!

Not sure that any of this answers my original question but its all interesting stuff.

And here is a link to that thread incase that is useful;
https://club8090.co.uk/forum/viewtopic.p ... 5#p7832164

[pfield69]

Great test circuit.
I would guess that if I jumped G to earth with a 680Ω resistor the light should trigger?

As regards jumping the level connector, I did short it out but it makes no difference light on, light off, light on & stays on (by on I mean flashing).

Would I be right to think there should be 10v on the gauge and therefore on the yellow/red wire?
so pin G=10v, #15=12v, #31=0Ω to ground, S=0Ω to coolant level connector?

[MidLifeCrisis]

I think I may be confusing you here;

Great test circuit.
I would guess that if I jumped G to earth with a 680Ω resistor the light should trigger?

That test circuit is a circuit that I built myself on a test bench (i.e. not in the van) to test the relay (I pulled the relay out of the van and attached it to this circuit to test if/how it worked). If you read the text under the test circuit it explains what I did and why.

As regards jumping the level connector, I did short it out but it makes no difference light on, light off, light on & stays on (by on I mean flashing).

OK - so you have pulled the connector off the coolant level sensor and then connected the two terminals of that connector together and the LED flashes continuously when you turn the ignition on?
Have you checked to see that one of those two terminals has a good connection to ground (i.e. 0Ω to gnd)?
Can you try grounding both of those terminals to a good ground and then turn the ignition on to see if the LED flashes then?

Would I be right to think there should be 10v on the gauge and therefore on the yellow/red wire?
so pin G=10v, #15=12v, #31=0Ω to ground, S=0Ω to coolant level connector?

Correct - except that G may not be 10V as the gauge has its own internal resistance.

[pfield69]

I am very confused by the circuit used on these things.

Would I be right in saying that the actual gauge is controlled by the fixed regulated 10v supply and then the changing resistance of the temperature sensors? This would explain why hot = less resistance = greater needle deflection. What I can't see is how the red light gets triggered. I guess the flashing is controlled by charging/ discharging cycle of the electrolytic cap but gauge deflection & red light appear to be controlled by the same yellow/ red wire #6(#4).

I also appear to have a connection issue on the flexi circuit as the light went out until I moved the 'dash' but I can't find it. If the yellow/red wire is the only wire that controls the gauge/ re light I may bypass the 14 way connector and go straight to the gauge.

Resistance to earth is 0Ω at coolant tank. Resistance from S pin in fuse box to earth whilst connector is jumped is open circuit. I need another pair of hands to check further ie to check direct from coolant level plug to fuse box pin.

[MidLifeCrisis]

I am very confused by the circuit used on these things.

Would I be right in saying that the actual gauge is controlled by the fixed regulated 10v supply and then the changing resistance of the temperature sensors? This would explain why hot = less resistance = greater needle deflection. What I can't see is how the red light gets triggered. I guess the flashing is controlled by charging/ discharging cycle of the electrolytic cap but gauge deflection & red light appear to be controlled by the same yellow/ red wire #6(#4).

The red light (LED) in the gauge is a 'flashing LED' so it will flash whenever power is applied to it.
The capacitor is what makes the LED flash for 5 seconds when you first turn the ignition key - so its purpose is just to give you the 'self test' function at the start.
There is a comparator circuit in the gauge that lights the LED whenever the resistance on the signal (temp sensor) wire reaches a certain level (i.e. therefore also when the gauge needle gets to a certain level of hot) - so as coolant heats up, the resistance of the sensor decreases, the gauge needle rises and at a certain point the LED light is powered on and flashes.
The really 'clever' bit is that when the 'coolant level relay' senses that the coolant level is low - rather than grounding the signal wire to the gauge (which would flash the light but also make the needle go to the hot position; which would misleading) instead it sends a rapid pulse of ground signals - just enough that the LED keeps flashing but not enough that the needle moves (as the needle is very slow reacting to change) - quite clever really!!

[pfield69]

Thanks for the explanation, it makes more sense now.

Further tests & maybe fault found.

continuity from coolant plug to S terminal is open circuit!!
continuity from coolant plug to connector in engine bay black box, 0Ω.
Continuity fro connector or coolant plug to connector on back of fuse box (terminal contains blue/ green cable (coolant level?) & yellow/ red ( temp gauge?)) open circuit.

Is there any other connections in this circuit were a break could be?

I did get a connection once and the light stayed off after initial test. So there must be an intermittent break

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Update:
wire is fractured just after connector in engine bay. All appears fine now (although temp gauge still a little low - is there more then one 2 pin sensor?).

Now I understand the circuit It is easily diagnosed. I don't have resistance values for the temp sendor at cold, normal or hot, nor for the coolant level sensor.