MGB & GT Forum

Trying to install electric fan to my B, but seem to be running into electrical connection problems (novice installer). I've connected it as best as i can understand but the fan isn't coming on. Any advice? See images.

Thanks.

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Cheers!
Hersh

I'm electrically pretty clueless, but what in the world is that wire grounded to?

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Drew Maddock, So. Calif. USofA

Drew, it's a temp ground to oil cooler bolt.

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Cheers!
Hersh

Does this help?

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Hersh-

I have the same setup on my '70 which I had to rewire (PO had it wired incorrectly). I'll take a look and let you know how mine is wired when I get home from work.

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Doug

http://www.mgexp.com/journal/OldBlue

Member - NAMGBR, ENMGR

Has the thermostat contact closed to turn on fan? Could jumper it to see if fan works

Sort of a dumb observation but they won't come on unless the thermostat clsoes (i.e. hot water...)

Roberts schematic is good to go. I personally would put thermnostat between G and 2 leg before the relay 12 oclock pin and then the 6 oclock pin goes straight to ground. Wired that way you could jumper 12V power on 12" o'clok pin and ops check the fans.

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The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G

If I remember correctly, there are 5 connections on that relay, not 4? I have the same thermostat in the radiator, and yes, if you jump the 2 terminals, the fan should turn on. I also have a switch in my console to turn it on manually.

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Doug

http://www.mgexp.com/journal/OldBlue

Member - NAMGBR, ENMGR

Yes in the pdf you can obeserve they also provide the 87a contact which opens, not closes when the relay is energised over the coil connections 85 and 86. My old Kenlowe thermostat also has such an extra connection. But neither on my Kenlowe, nor in this situation is 87a used. If the relay is energised contact 30 to 87 connects + battery to the fan motor(s).

Following Roberts diagram, the bridging of the thermoswitch (3) connections will simulate the hot situation and the fan(s) should run. Kenlowe also provides a seperate switch for this bridging, as a kind of manual override. This connection setup puts switching in the earth loop, unlike the factory pdf which makes switch (3) connect the + line to the relay 85, with 86 on earth.


PS Robert: you forgot to draw the 85 and 86 numbers on your simplified drawing, Assuming that 85 is on + battery the thermostat switch (3) is on 86. I feel it is wiser to seperate the constant + battery on relay 30 from the switched + battery on 85, taken after the ignition switch. The factory PDF shows the same split. So 30 connects to the bottom fuse and 85 on the one higher up





Edited 1 time(s). Last edit at 2015-07-30 08:35 AM by Donthuis.

My current set up is as follow:

Red - fuse box (4)
Black - ground
Orange w fuse (+) - fan
Yellow from thermosensor - fuse box (4) --> instructions call for ignition switch (lost me here)
Brown thermosensor - relay
Blue fuse (fan 2) - not used
Green a/c clutch/manually switch - not used

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Cheers!
Hersh

That would be a fused connection that is hot ONLY when the ignition is switched on.

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Doug

http://www.mgexp.com/journal/OldBlue

Member - NAMGBR, ENMGR

Doug, would this be applicable only if i want it to turn on with ignition as oppose to have it hot all the time so it turns as long as the water is hot till a certain temp?

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Cheers!
Hersh

Then you follow exactly the pdf diagram and not Roberts. The relay is activated on switched + battery via the thermostat towards contact 85 via brown while 86 is via black is put to mass.
Yellow then goes to switched + battery on the one but lowest fusebox postion. Red with the constant + battery should go to the lowest position of the fusebox. Black to mass/earth. Nothing wrong!

It is a very simple circuit: if you bridge (interconnect both of its connections with a separate wire shortly) the thermostat, the relay should come on and the fan turn. Are you sure the other fan connection, the minus one is firmly grounded? As always using a testlamp is easiest to check + battery on the red and yellow wires and subsequently on brown when the thermostat is bridged

PS I distrust thermofeelers pushed through the radiators, they tend to come up later than the ones in the hoses. But by bridging the thermostat you will check the circuit first, success...

Three camps here...

On all the time
Switched
Was on all the time and got tired of hearing the fans and switched back

I am in the switched camp. Little need to force the fans to run after the alternator is not making juice. Especially if the radiator/puke tank system is working properly.

Manual fans don't run after the engine shuts off -

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The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G



Edited 1 time(s). Last edit at 2015-07-30 10:49 AM by Ex-Calif.

Don
Do you mean Yellow to #6 and Red to #8?

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Cheers!
Hersh