Wiring Diagram for fan override switch

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Wiring Diagram for fan override switch

Post by biofos on Tue Mar 07, 2017 11:42 pm

I think I read somewhere on the forum that Woodie recommends a fan override switch whether or not you have over heating issues with your Jet/Porter.

I tested my cooling system out before changing the coolant I found the thermostat opens at 83C and the fan comes on at 98C. After changing the coolant these figures changed; the thermostat opens at 84C and although I've run the engine up to 102C the fan fails to start. I took some advice from the local radiator company. New coolant increases the boiling point and pressure. Most 'modern' cars don't operated the fan until 105C. Thermostat opening changes are also down to new coolant. Is the heater now a bit hotter? Yes. Good, don't worry. Is it leaking fluid? No. Good don't worry. Is the expansion tank level constant? Yes. Good, don't worry. Are the top and bottom hoses about the same temperature? Yes. Good, don't worry. Has it boiled? No. Good, don't worry. It's a Hijet/Porter - Oh! - Should be OK.

I followed all the advice about coolant changing from this forum, posted by folks a lot more experienced and am confident it's fine. I also bought one of those Head-Up displays that plug into the diagnostic socket. £30 for a lot of peace of mind is a bargain I think. The thermostat opens at 84C every time. On any run the temperature varies between 84 and 87 (uphill). If I put the heater on full the water temperature drops by 2C. My only concern is the thermo-fan switch. I really don't want to be sitting in traffic on a hot day waiting for the water to get to 102-3-4-5C before the fan starts.

This brings me to the point of the post - is there a wiring diagram of the override switch anywhere? I am useless with electrics and need to be told what wire goes to what other wire, what goes to ground and what goes to the switch. I assume the override switch is spliced into the low amp side of the fan relay. I know where that is and have decided where the switch will go. It's the bits of wire in the middle that lead to my confusion.


John (biofos)

Posts : 15
Join date : 2016-11-23
Location : Richmond, North Yorkshire


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Re: Wiring Diagram for fan override switch

Post by Woodie on Wed Mar 08, 2017 8:29 pm

Hello Mr Phosphate. If you send me your email address or preferably a WhatsApp number as I can send up to 15 pictures at a time to : thehijetmaniow@gmail.com
I will over the next few days take some pictures and do a step by step guide of how to fit a switch into the circuit.
I have bought a load of Illuminated Rocker Switches and new Relays and I am intending to make a small batch of ready to fit kits with wiring and connections and wiring instructions for those who want to fit a Radiator Fan Overide Switch but don't know where to start or don't have the confidence to have a go themselves.
If anyone is interested, please let me know on my email address with if possible a mobile WhatsApp mobile number as well.

I am gradually finding my feet again and handyman work is trickling in. So bear with me and I will have a go at this over the next week on wet days stuck in the Garage in the dry.
I have a number of pictures, but not on this Tablet so I will have to Download them from my phone later on tonight.

Posts : 855
Join date : 2016-01-24
Location : Niton, Isle of Wight.


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