Before I remove the dash...

[Midge]

Hi Folks, I have a problem to tackle - but first I'd like to say thanks for the wealth of cracking info/tips/help that I've already taken from this forum.

It's the articles in here that have given me enough confidence to try a bit of DIY repair work, despite my inexperience, so cheers for that.

OK, the problem I need to fix is that the temp gauge needle has not yet appeared from the left hand side of the dial.

Fuel gauge works fine (well, it moves) so from looking at other posts on here I think that rules out the dash voltage regulator.

I tried to bypass the "43" Relay with a wire jumper to make the needle move, but no joy. See here: https://club8090.co.uk/wiki/Co ... alfunction

Now I must admit that I had no spade connectors so just jammed in a piece of wire - but the red light behaved as per normal, with an ignition self-test, and when I removed the jumper (engine running) I got another few flashes from the light - so I believe my spade-less jumper-test did its job.

So.... Does the jumper test mean that the fault is most likely with the gauge unit itself - literally a broken needle or dodgy connection?

Is there anything else I can do before taking the dash to pieces? Would the "43" Relay have an associated fuse I should be checking - can't see any reference to the temp gauge in the fuse list in the owners manual...

Possibly related is another fault - I'm only mentioning this in case it helps diagnose this one.

Switching the air blower on to full belt is blowing the 20A fuse immediately. I guess to dash is coming out to fix that one anyway - but I'm way more concerned with the temp gauge needle at the moment.

Many Thanks for any advice, Cheers!

***E D I T to add - it's a 1989 1.9 petrol watercooled four speed Komet

[MidLifeCrisis]

Now I must admit that I had no spade connectors so just jammed in a piece of wire - but the red light behaved as per normal, with an ignition self-test, and when I removed the jumper (engine running) I got another few flashes from the light - so I believe my spade-less jumper-test did its job.

The important bit is in the detail of what you mean by "when I removed the jumper (engine running) I got another few flashes from the light"; With that jumper installed you should have got a flashing light all the time (and the needle should have gone to 'very hot'). It's possible that as you 'jammed in a piece of wire' that you might have only made a good connection as you pulled out the wire - hence the 'few flashes from the light'
Is this what happened??
I'd repeat that test if you can .......

.... if that makes the light flash but the needle doesn't move then it proves that the wiring to the gauge is good (cos the light is behaving correctly) and the gauge needle is bad; if the needle doesn't move and the light doesn't flash then it might suggest that the wiring isn't good - so its important to confirm what the results of that test are??

[syncroandy]

If the sender and wiring is OK you should see around 1200 ohms (at room temps) across pins 6 (G2 sender) & 3 (Ground) on the T14 edge connector.

If not, fix this before suspecting the dash.

[Midge]

With that jumper installed you should have got a flashing light all the time
I'd repeat that test if you can .......

Hey, hello MLF - have read quite a few of your posts whilst looking into this problem, so it's good to read your response to it!

Can't believe I failed to read that original post thoroughly, yeah I see what you mean now... Trouble is I still need to build up a toolkit, and I'm still waiting on the Haynes manual from Amazon, but I'm beating myself up for buying a busted van and trying to sort it sharpish so we can have our first trip out. Bit less haste needed, I know, I know.

I'm now looking for a pukka jumper-lead with spades on, to see what the score is. Cheers!

[Midge]

If the sender and wiring is OK you should see around 1200 ohms (at room temps) across pins 6 (G2 sender) & 3 (Ground) on the T14 edge connector.

If not, fix this before suspecting the dash.

Hi Andy, thanks for the reply. Will move onto this when I have the test results.

Sounds like there's hope for Kevin yet, though he is at the mercy of a cak-handed tool-wielding clown so please pray for him.

[MidLifeCrisis]

I'm still waiting on the Haynes manual from Amazon, but I'm beating myself up for buying a busted van and trying to sort it sharpish so we can have our first trip out. Bit less haste needed, I know, I know.

I'm now looking for a pukka jumper-lead with spades on, to see what the score is. Cheers!

While you're waiting on that Haynes ... did you see this pic?

Hopefully this should help you understand what does what.
For instance when you are sticking that 'jumper' in those terminals - you are actually jumpering between the 'G' terminal and the '31' terminal of the '43 Relay' (so that effectively grounds the signal wire to the gauge - which simulates the temp sensor seeing a very high temperature i.e. your light should flash and the needle should rise to show 'hot')

[Midge]

Hey yeah, I saw that one during my research - it's mega clear what's going on there.

It was that diagram that enlightened me to the dual purpose aspect of the gauge, as I had no idea it concerned fluid level at all, thought it was just temp...

As I see it, the temp is like it's primary purpose, and would still function even with relay failure, as the relay only serves to piggy-back the warning signal if the fluid level demands it. Faking 'low level' at the relay should bash the needle for sure!

Usual story with the spade hunt. I found a bag of female's and a set of crimps, but not a male to be seen anywhere.

Off shopping tomorra lunchtime - any old spade or does it have to take a specific load?

Cheers

[MidLifeCrisis]

Any should do it - small or large will do for this simple test.

[syncroandy]

Hmm, well take care shoving bits of wire into your relay plate.. one slip and you'll have burned fingers and possibly a wrecked relay plate. Definitely not an approved workshop procedure ! I'll get my coat..

[Midge]

Hmm, well take care shoving bits of wire into your relay plate.. one slip and you'll have burned fingers and possibly a wrecked relay plate. Definitely not an approved workshop procedure ! I'll get my coat..

Wise words Andy, and believe me I actually do know better, just got a bit carried away...

[Midge]

Reet then, the results are in! Shorting/jumping the relay brought the needle flying into action - that's the first time I've seen it, yay...

I guess this points towards a dodgy temp sender, coming from the rear of the thermostat as I face the rear of the van?

Advice taken from here suggests I next try shorting the green/blue wire from the sender end, to the engine block as earth. This will do the same trick as with the relay - and prove the wiring is all good and just a sender unit needed?

I bet the sender part number is on this forum somewhere

[MidLifeCrisis]

Advice taken from here suggests I next try shorting the green/blue wire from the sender end, to the engine block as earth. This will do the same trick as with the relay - and prove the wiring is all good and just a sender unit needed?

Sounds about right - but I think its a sensor with a red/yellow wire going to it that you're looking for.
The blue/green wire goes to the coolant level sensor (i.e. the sensor that the '43 relay' uses).
Ground the red/yellow wire to test the temp sensor and see what the needle does .... ??

[Midge]

Ground the red/yellow wire to test the temp sensor and see what the needle does .... ??

Nice one, will do. First light tomorrow I'll have a roll around the floor.

I need to get a good look at the sender anyway as there are 4 different ones on JK that all seem to qualify for my 1989 DG, bizarre...

Also want to fit a new thermostat while I'm at it, bit of piece-of-mind an' all that. Bet there's 4 to choose from, eh?

[Midge]

Have now tested the sender end. Needle came out of the trap and bolted across the dial like a good 'un. So the red/yellow wire is behaving itself and the sender is the culprit, it seems.

Not sure what the other wire from the sender is all about, as it was disconnected (for the test) so all I can imagine is it provides the earth? So should I now test by shorting the 2 wires at the sender end to check the non-red/yellow cable...I think it was brown?

The sender itself is going to need a bit of rough handling to get it out - the wire clip is all rusted/snapped and looks well stuck in the grooves on the fitting. I'll tap it out as lightly as I can to try avoid damaging the housing.

Newbie question - will any fluid start pouring out when the sender is removed?

So the sender is 2 wires and a square black plastic lumpy shape. Is that because only a black one will fit? I have no idea if the previous owner put the correct one in and I don't want to compound the error if that's the case...

So many questions! Haynes arriving a week tomorrow, I'm such a cheapskate when it comes to postage.

Thanks for any advice given

[MidLifeCrisis]

Not sure what the other wire from the sender is all about, as it was disconnected (for the test) so all I can imagine is it provides the earth? So should I now test by shorting the 2 wires at the sender end to check the non-red/yellow cable...I think it was brown?

Yep - that will be the senders ground connection - so as you say, connecting that 'brown' wire to the red/yellow should see the needle heading for the hot again - its a good final test to ensure that it is the sensor that is the issue.

Newbie question - will any fluid start pouring out when the sender is removed?

It shouldn't pour out but it might 'seep' out - not sure exactly how you sender is oriented (I have the older style) but its possible that coolant may leak out when its removed - might be wise to have something to hand to plug the hole (like the new sensor for instance!!)