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Super Moderator
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Discussion Starter #1
I removed and replaced the two wires on this switch/ thermal sensor. My factory manual doesn’t show this on the manifold but looks like a cooling fan switch. But this usually resides on an aluminum pipe like my late 88.

I thought it was water temperature sensor as now my gauge does not work reliably. I shows 0 when fully hot and randomly shows 80-90C.

But water temperature sensor is a single wire device bolted new water pump.

So what am I looking in this photo (yellow wires)



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Discussion Starter #3
Ugh. Now I can’t figure out if I reversed the wires. Didn’t realize the high temp and thermo time switch were merged into one device. I switched positions thinking I got it wrong but maybe damaged it if wrong wires crossed.


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Wingless Wonder
1988 Esprit Turbo
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Def. the High Temperature Switch.

If you look on Page 56 of Section LD, you will see that it doesn't matter which terminals the wires are connected to. It just provides power to the the coil of the Fast Warmup Relay. (The Yellow wires provide input power, pink/brown goes to the relay coil, eventually ;)) It should be 'OPEN' at normal operating temperature (see page 60).

No polarity, no harm, no foul.
 

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Discussion Starter #5
Def. the High Temperature Switch.

If you look on Page 56 of Section LD, you will see that it doesn't matter which terminals the wires are connected to. It just provides power to the the coil of the Fast Warmup Relay. (The Yellow wires provide input power, pink/brown goes to the relay coil, eventually ;)) It should be 'OPEN' at normal operating temperature (see page 60).

No polarity, no harm, no foul.
OK - but now the head-scratcher - Those were the only 2 wires I knowingly touched (removed them briefly because the fuel line was intertwined). Once I put them back my water temperature gauge no longer works correctly (!). I know, I know - it should not be related but that's what I'm seeing after re-installing the back-flushed injector. I even got a FAN FAIL light briefly - it acts like something electrical really got disturbed while removing this injector.
The water temperature sender is located down low on the front of engine on the water pump housing (?) and my grubby paws went nowhere near that sender.
So it's a bit baffling to me.
 

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Wingless Wonder
1988 Esprit Turbo
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5,861 Posts
You could have jostled the gauge connector near the thermostat. Or, moving the Hi Temp wires pulled the gauge sender wire.

The gauge sender is located on TOP of the water pump, with a clip-type connector that has to be the Poster Boy for the term LOOSE CONNECTION. Try pulling it off (straight up) THREE times and see if that makes the gauge more consistent.

Otherwise, just monitor the view out of the rearview mirror for signs of steam. :eek:
 

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Discussion Starter #7
late update - so I got my smog test issues out of the way.
However, my water temperature gauge has gone even more wonky
1. on dead cold start, the gauge immediately reads max 140C (definitely wrong)
2. once car is running, it was doing random temperatures - nothing made sense

Now, the gauge is:
1. random reading below 2K RPM
2. At steady state freeway driving (65 MPH, 3500 RPM) the gauge appears correct at 80C.
3. whenever RPM drops below 2500 RPM, the gauge reads 'hot' (not actual) and can go back to 140C at stop

I did not touch directly anything near the sensor (haven't actually seen it yet) but the behavior changing to 'works at 3500 RPM' is very odd.

Once I get access to car again, I will check the sensor, but wondering if anyone has seen such sporadic behavior?
For reference, my voltmeter for a long time was inaccurate, but a few months ago, it started to work correctly (based on a lighter socket voltage for comparison). I did nothing actively to fix it - it just 'fixed' itself.

I do have the Moss Motors voltage stabilizer since 2016, but cannot attribute any issue directly to it:

Moss Motors voltage stabilizer
 

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In some cases, erratic temp readings can mean you have air in the system and it has to be bled. Can also be due to a bad/dirty electrical connection.
 

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Wingless Wonder
1988 Esprit Turbo
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5,861 Posts
Have you checked for resistance between the thermostat outlet (where the sender is located) and battery negative?

Gremlins can occur due to the 'dissimilar metals' syndrome, and sometimes all it takes to fix it is to back off a mounting bolt one flat, and re-tighten.

IIRC your car has a big A*S extra ground wire to the intake manifold for JUST that reason.,
 

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It has to be an electrical problem as there is no other way the temp would spike like that when cold. So that then limits the problem areas to sensor, gauge and/or the wire in between. Given your recent work in the engine compartment I'd start by checking the continuity of the wire. If it's intermittently grounded or open somewhere it could easily be causing your problems - including at different rpms due to variations in engine vibration. Be sure to closely check the connectors as a dodgy electrical connector was ultimately the answer to a hard to solve problem with my fuel injection.
 

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Discussion Starter #11
I remember something Tim E said a long time ago when I got my first Esprit in 2011 - it had new clutch master cylinder and slave cylinder - barely 1 month old and NEW, not rebuilt. I described an issue with the clutch and he zeroed in on the hydraulics. "But, but - they are new!" He said (paraphrased) "I'm going by the symptom - regardless if the hydraulics are new, they act defective and you have to assume they might be.". And sure enough - the new master cylinder was bad.

So, I say "I didn't touch anything near the water temperature sensor.". Well, everything points to the fact I must had done SOMETHING nearby and I simply don't remember.

The car is back in the work garage after finally finishing the work to pass smog. I was reluctant to keep at home in driveway - I found evidence that someone either climbed on rear hatch or put a heavy weight on it - there are 6-8 cracks in my rear louvres that were not there before. I know they are new cracks as earlier this year, I bought 'black trim' coating and tried to make the louvers more black - didn't see any level of cracks like I do now. There are also people checking cars at night for open doors so all the neighboring streets security cameras confirm it. Garage is filled with home remodeling supplies so work garage is the safest for now.

Thanks for the tips - will try to check it out Thurs or Friday.
 

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Dreaded Prior Owner
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The rivet holding the flag connector onto the body of my sensor worked loose, and I had to add a bit of solder to restore the connection. Might be something to check.
 

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Discussion Starter #13
Solution found:

As Atwell speculated on the cause and Van O sent a picture (I had a hard time interpreting the service manual for the water temperature sensor location).
Yes - the spade connector had fallen off, BUT was touching the sensor intermittently while driving. That explains the weird behavior.

Picture below shows the spade connector completely off and touching the sensor. I sprayed some brake clean on it (and put plastic shield on timing belt) and put it back on.

Life is good.

Many thanks for all the help! I still don't know how I got a wrench down there while replacing fuel injectors/spark plugs, but I must have done SOMETHING!

Eddie

1265976
 
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