Fan temp switch/sensor

[ogdensnut]

hi all,
sorry to bother, but i've scoured the site, and haven't quite hit on the confirmation i'm after (though i now have a good idea i hope! - though i'm certainly no mechanic!)

i've had the car since April, running fine, MOT passed with a few minor advisories in November - main thing that i've noticed and want to sort now, is that the fans / auxillary pump are not coming at all if/when engine gets hot.

i'm happy the main thermostat is working as once the engine up to temp, it then stays at halfway point cool so long as i'm moving at speed, which (i think!) tells me the radiator is doing it's job just fine.
i'm happy that the temperature gauge is working well as once engine is on, it gradually increases up to halfway and then hovers though whilst driving unless get caught in traffic etc when it gradually increases as i'd expect before dropping back down once i'm moving again.

however, i suspect there's an issue with the fan switch as i've never heard the fans kick in (or pump turn off after engine off) despite having multiple times when the gauge has read between 3/4 and top notch, so this is obvs a concern as don't wana be doing any damage/overheating.
i've earthed the connection which works as expected giving me either fans on and/or pump on (depending on ignition status) - and so i'm guessing this means that fuses/relays are ok (and i checked the ones in binnacle region and fuses looked ok to me.

i've removed the sensor and cleaned off the minor corrosion that was present, but let engine get hot again today and still no fans coming on.
so is it as simple as getting a new sensor, or is there still a chance that it's some other electrical issue (i'm the guessing former as it all seems to work fine when earthed with my paperclip!)

...and if i do need a new sensor - any suggestions what to go for please as i found the page in the wiki but none of the 'standard' options listed appear to be available any more, although there seem to be several of the low-temp ones i can order having gone down various rabbit holes:

FAE 36660, VEMO V32-99-000, METZGER 0915209, lots of brands with code - N35018840.

just wondering if anyone has ordered one recently perhaps, so can confirm an instock version (standard or low temp - i'm not too worried!) that will definitely be compatible with the electrical connection please
thanks in advance, i'm learning so much here... but long way to go clearly..!

cheers
ol

[stevie-a]

I had concerns about temperature gauge when I bought my car this time last year, turns out that the Elan Temp setting are is not like any other car I have had (surprise surprise ) when driving it will sit looking cold say quarter gauge when at idle, It will go up to three quarters and just after the three quarter the fans should come in, and take it down to halfway where it will proceed to go between halfway and three quarters when it idle, when starting driving it get down to quarter again hope this helps

[ogdensnut]

Hi and thanks so much for your swift reply, yes that's v helpful as confirms my understanding of what should be happening ...but the issue is that my fans have never kicked in, even when I've let the temp gauge creep up to 'almost full' so am now quite concerned that if I'm ever stuck in proper traffic one day in summer, I may come a cropper..!

Hence want to confirm best action I can take to remedy lack of fan-assisted cooling please,
Cheers
Ol

[chrism]

viewtopic.php?f=134&t=30441&hilit=thermostat+fans

ogdensnut, there's a good thread on LEC informing about fan/aux fan/sensor operation and I think the above link might work...

I think I'd test for the fans + aux fan first by following the post in that thread. If they're okay I'd see if someone local would show you 'ElanScan', which would show your engine op temps as you warm up from cold (say). There's an EScan warm-up graph of my own fan on that post for comparison - and it should show if your thermostat is behaving properly, too.

If you need a new fan temp sensor switch (I think there's also a seperate ecu temp sensor) my pal peteoddcar has a non-lotus-priced, easily-obtained alternative that works just as well - and it's fitted on his car permanently. I'm sure he could put one together for you.

It's already been pointed out that the temp gauge is unreliably, non-linear so don't pay too much attention to it imo, but I reckon an ElanScan would be a useful thing to do anyway and would prove most informative.

Look at the link first tho' (if it works; otherwise look for it on LEC) and let us know if it helps with your problem(?)

[stevie-a]

Also watch this, might help test the pump and fans

https://www.youtube.com/watch?v=tfj3dUZTYJY

[Tuga2112]

im currently at work. so this is a TLDR reply.

but testing if the fans or recirculating pump are working is very easy (the switch is a bit more involved, specially as it appears your temp readings are no matching the factory standard )

you just need a paperclip and disconnect the sensor. and short the tab to ground

with the ignition off. you get the recirculating pump running. with the ignition on, you get the fans. (you dont need the engine running)

if this is not clear. i can post a quick demo on youtube later today... if i remmeber

[ogdensnut]

hi everyone,
cheers for your swift responses -

'chrism' - yes i already have elanscan, so great idea to try giving that a go, and i'll see what temp it goes up to - as suspect the fans should be kicking in, but they simply never do...!
and i'd seen that thread you've mentioned cheers, but think i got distracted scanning through it with the mentions of vampire drain etc

and 'steviea' thanks for video link and 'tuga2112' - the paperclip description - but i've already done that testing (see my original post) and can confirm they both worked ok, hence my assumption the issue is the switch itself rather than fuses/relays etc ?!?

cheers all
ol

[chrism]

Erm, EScan should tell us what the ecu thinks that the engine temp actually is via its own separate sensor (the engine management coolant temp switch, CTS).



Presumably if this says 'warmed up sufficiently' then the fan temp sensor (rad fan thermal switch) - which you've already established as okay - is then instructed to take over and controls things in the way we all know and love. If the CTS doesn't, then I reckon it's a candidate for replacement. That EScan plot should reveal all...

I'm suspicious; I'd also welcome that EScan to convince us that the thermostat is behaving itself and opening up around 82C.

[ogdensnut]

hi all,
as per my previous message, i've hopefully successfully uploaded image below of the temp (gradually increasing at idle sat on my drive), until the temp started dropping a little at 85c, presumably as thermostat valve opens to allow radiator function... which is a little higher than the 82c you mentioned chris but hopefully not of any concern.

i then thought it'd be interesting to log the temps it recorded based on the needle position on the notches on temp gauge, and had the following results

needle starts moving - 55c
1/4 mark - 70.5c
1/2 - 82c
3/4 - 90c
7/8 - 95c
15/16 - 97.3
top notch - 101c

at which point i chickened out going any higher as wasnt sure how high it was sensible to let it run... but i seem to remember reading somewhere that the fans 'by design' are only supposed to kick in at 107c, in which case (despite being at top of temp gauge scale) it seems i'm still 6c too low for that... which would prob explain why i've never heard them start, as i've not let needle go any higher out of fear of doing damage..! so yes - a rather contrary gauge a you said in first reply stevie..!

so i guess my question now is: am i safe to let engine run right up to 107c (monitored on elan scan) to see if i finally get some fan action, or... shall i just relax (relatively) safe in the knowledge that it's simply prob not getting hot enough and move on to worry about the next thing!

cheers again everyone, can't believe i didn't actually think to use the elancan i'm so luck to have..!!
ol

[chrism]

ogdensnut your graph's approaching 40C at the bottom end so that's too high if you ran it up from overnight cold - as I did in my own plot. CTS sensor's gotta be 'wrong' if that's the case?

A bit high at t'stat opening unless a prev owner fitted a high temp unit. If so I wonder what the reason was(?) but ~10mins is roughly the same warm-up time as mine. (Again CTS might be reading high?)

And yes, I'd have let it go above 100C. I haven't actually looked to see if it happens but I gather you can get live temp data from EScan to monitor? Peteoddcar measured his fan cut in ~110C using a thermocouple, tho' like you I have seen 107C quoted from other sources.

I set my own fans low at 104C and I must admit they only come on if left idling with no airflow after warming up - so it might be that your fans won't 'play ball' in these temps. In the high temps earlier in the year they came on for a short period after 5 mins or so idling, after a run, and I felt reassured that in my case the process was working okay...

(I had MGTF135s before and overheating/hgfs were always in the back of my mind...)

If pushed I think I'd spend ~£15 throwing a new CTS on. After all the original's gotta be 30-odd years old, then do another EScan and see how the new temps compare. Also it'll enable you to make sure your system's been properly bled?

This might be something to look at first. I wonder if an airlock could cause this?

[ogdensnut]

cheers chris
so sorry, i forgot to mention in my message that the first couple mins of the 'experiment' were recorded on a separate trace (as i had never used elan-scan previously so wanted to check it worked ok before i took it up to high temps..!)

so it originally started appropriately at 5c, and went up on same trajectory as the rest, it's just that after i'd ensured i could generate a graph on the software, i started the second 'recording log' which meant the coolant was already at 38c approx as per graph, so think that's just a false alarm - sorry again for any confusion.

but imagine that probably looks more reassuring now i've (belatedly) provided that context..!
cheers again for reply, really appreciate it - this site is invaluable for idiots like me..!
ol

PS - yes you can see live readings whilst connected to laptop, but i can only seem to generate a graph once finished 'logging'

[chrism]

Hey, we've all gotta start somewhere. Spannering an m100 and EScan-ing are steep learning curves and nothing is obvious.

For much of the time you have to find out what you don't know that you don't know, then find out how to know it

Usually someone's been there first tho', thankfully.

[peteoddcar]

Chris has been nagging me me about not visiting the forum often enough!
It sounds to me like you have a standard Vauxhall J car ( Cavalier ) temperature GAUGE Sender, the Instrument pack is from a Cavalier modified to have red decals.
The Elan gauge sender is a unique part -
Let her run to 110 on Elan Scan and maybe the fans will kick in.
The M100 Isuzu engine generally runs its coolant hotter than the cast iron J car engine, so 110c on that sender gauge set up will show full scale hot.

The Lotus temp sender part number is A100M0042M