Thermostatic fan switch

Talk about the E-Type Series 3

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thermojac
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#1 Thermostatic fan switch

Post by thermojac » Fri Jun 17, 2022 10:03 am

:I am replacing my faulty 2 pin thermostat switch with an 'Otter" type switch but when I test it in boiling water the resistance goes from 17 meg to open circuit 🤔. I was expecting it to short out between spade connector and body of until. Am I being stupid or missing something here?
John

S3 FHC 1972 Manual

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MarekH
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#2 Re: Thermostatic fan switch

Post by MarekH » Fri Jun 17, 2022 9:01 pm

No and no.
You'll have to buy one that works.

kind regards
Marek

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Allrand
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#3 Re: Thermostatic fan switch

Post by Allrand » Sat Jun 18, 2022 1:26 pm

The unit sounds OK, it'll only short out to the body of the unit when it reaches switch on temperatue.
Randall Botha
'64 3.8 fhc & '51 Mk 7

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thermojac
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#4 Re: Thermostatic fan switch

Post by thermojac » Sat Jun 18, 2022 2:05 pm

Thanks Marek. I thought I would safe buying from SNG 🥴
John

S3 FHC 1972 Manual

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Craig Balzer
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#5 Re: Thermostatic fan switch

Post by Craig Balzer » Sat Jun 18, 2022 4:57 pm

I can recommend Cool Cat's
https://www.coolcatcorp.com/Merchant5/m ... e=Cooling3

SNG Barratt's is cheaper but is only the otter switch.
https://www.sngbarratt.com/English(US)/ ... a0b4f9d04e

What condition is your T-pipe in?
Craig Balzer
Colorado Springs, CO, USA
1972 Series III OTS, 4-Speed (soon-to-be a Guy Broad 5-Speed), A/C, CWW

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MarekH
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#6 Re: Thermostatic fan switch

Post by MarekH » Sat Jun 18, 2022 6:56 pm

A one pin switch would indeed have to connect up the switch body to complete the circuit. The s3 loom expects a two pin switch so it sounds like you'd have to make an adapter if you were to use that switch.

The switch on and off temperatures are linked to the thermostat rating.
The s3 used 82'c thermostats.

Using the wrong spec Otter switch would mean the fan comes on and goes off "not quite in sync" with the expected water temperatures given that the thermostat sets the lower operating bound of that temperature range.

Expect the s3 radiator to drop the water temperature ~15'c

kind regards
Marek

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Series1 Stu
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#7 Re: Thermostatic fan switch

Post by Series1 Stu » Sat Jun 18, 2022 9:36 pm

thermojac wrote:
Fri Jun 17, 2022 10:03 am
:I am replacing my faulty 2 pin thermostat switch with an 'Otter" type switch but when I test it in boiling water the resistance goes from 17 meg to open circuit 🤔. I was expecting it to short out between spade connector and body of until. Am I being stupid or missing something here?
Do you really mean open circuit, or do you mean short circuit? The latter would be correct.

Regards
Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
'69 Daimler 420 Sovereign
'78 Land Rover Series 3 109
'94 X300 XJR basket case

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thermojac
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#8 Re: Thermostatic fan switch

Post by thermojac » Sun Jun 19, 2022 3:07 pm

T pipe is in good condition Craig.

Marek, I ordered pt no C37392 > C45086 from SNG which is the part listed for the V12 so I would expect the temp rating to be correct. You are right about the loom and I was planning to connect the spade to W2 and the body to C3 terminals on the relay.

I did mean open circuit Stu and I was expecting a short circuit.

I will get onto SNG tomorrow for a replacement.
John

S3 FHC 1972 Manual

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baganz.sven@web.de
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#9 Re: Thermostatic fan switch

Post by baganz.sven@web.de » Wed Jun 22, 2022 12:19 pm

I also installed the coolcat version.
Works without problem.
sven
Sven
'71 S3 coupe LHD manual

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thermojac
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#10 Re: Thermostatic fan switch

Post by thermojac » Mon Jul 11, 2022 7:53 pm

Sorry for taking so long yo conclude the string. New thermostat acquired and system working well :smile:
John

S3 FHC 1972 Manual

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rswaffie
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#11 Re: Thermostatic fan switch

Post by rswaffie » Mon Jul 11, 2022 9:58 pm

Good news. It got a good test on Sunday!
Richard

S1 3.8 FHC Opalescent Golden Sand with Tan Trim 8895**
Now enjoying my diy nut ‘n’ bolt restoration. :swerve: :wrench: :hammer: :fingerscrossed:

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thermojac
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#12 Re: Thermostatic fan switch

Post by thermojac » Tue Jul 12, 2022 4:18 pm

Much to my significant relief :bigrin:
John

S3 FHC 1972 Manual

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