Lotus Elan

Help needed with Wiring the heater fan switch

PostPost by: keith stringer » Sat May 27, 2017 5:25 pm

I have recently sprayed my car and renovated the interior of my lotus Elan se4. After fitting the new dash I can't get the heater fan to work. The switch I took out was a 2 spade two position but broke apart on removal I purchased another from Paul Mattey but it was a 4 spade type 3 position switch. No matter how I wire it to the switch I cannot get it to work. However I will point out that on inspection of the heater unit there are two wires coming out that go to the switch? One Green and Yellow wire and the other green and black. Two other wires come out of the side of the fan one white that goes to a Earth on a bolt at the back of the dash the other is black and purple and this goes into the heater. On my wiring diagram of the s4 it only shows one win in and a earth coming out? Is mine a two speed heater
I used a green wire that originally fed power to the switch and connected it to the green and yellow wire, this then gave me 12v down the green and black wire.
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Keith
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PostPost by: elanfan1 » Sun May 28, 2017 11:02 am

Can't help you with the technical bits but AFAIK your Heaterbox should have a resistor inside allowing for fast and slow operation so you should have a 3 position switch - I may have one - let me know if it helps.
Steve

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PostPost by: keith stringer » Sun May 28, 2017 7:04 pm

Hi Steve,
Thanks for the offer but I already have one I purchased from Paul Mattey and tried but to no avail. It's just the wiring of the switch I am having trouble with. I wired the green wire which is live to the switch which then gave me a live to the fan which then gave me a live back down the green and yellow wire. I then tried wiring this back to the switch? But no luck, it's like there should be another wire on the switch.
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PostPost by: nmauduit » Mon May 29, 2017 9:38 am

I don't recall specific difficulty hooking up the 2 speed heater on my elan s4 : as per Lucas colors code (http://www.barnblinker.com/category/wiring-harness/ http://www.lotus-europa.com/manuals/mis ... lucas.html ... etc) , green/yellow should be "slow" speed (i.e. through the resistor) and green/slate should be the "fast" speed. You may need to pay attention to grounding issues, as is often the case on our beloved plastic autos...

also from :
lotus-twincam-f39/plus-heater-overhaul-t22942-15.html

"
The high speed wire from the switch connects to the double terminal on the resistor.
The power wire from the fan motor connects to the double terminal on the resistor.
The low speed wire from the switch connects to the single terminal on the resistor.
The ground wire from the fan motor connects to ground.

On the 'high' switch setting the power to the motor by-passes the resistor thru the double terminal.
On the 'low' switch setting the power to the motor goes thru the resistor (resistor in series with motor).
"
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PostPost by: elanner » Mon May 29, 2017 11:11 am

Presumably 12v coming down any wire out of the fan is just a floating output from the supply voltage (in other words, it's all part of the same circuit)?

Are you saying the fan isn't working or the switch isn't working? Ignoring the ground wire, the fan has two wires coming out of it - one is green/yellow, the other seems to be either green, green/brown, green/black, or green/slate. One wire for each speed. Can you simply bypass the switch and confirm that 12v applied to one or the other wires turns the fan on, fast and slow?

Meanwhile, the switch should be three position (off, slow, fast) and needs three spade connectors, one for the 12v supply from the battery, which is green. The two fan wires then fit to the other spade connectors. Since your Paul Matty switch has 4 spades you'll need a multi-meter to figure out which spade does what. Four spades sounds slightly suspicious but perhaps it's a double action switch where the first position connects one pair of spades and the second position connects the other pair. In which case you'll need to jumper the 12v supply to the two supply-side spades.

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PostPost by: Craven » Mon May 29, 2017 3:29 pm

May help
p1030194.jpg and
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PostPost by: bob_rich » Mon May 29, 2017 3:49 pm

Hi Keith

Cravens drawing should work fine and I think some Elans are done like that. But the some of the +2's worked differently in that the 12V went to the motor and then the switch would connect the other motor terminal either directly to earth (fast) or to earth via a resistor of around 1.0 to 1.5 ohms for slow.

Have attached a drawing from the +2 manual. If you have a 4 terminal 3 position switch then you should be able, with a test meter, to fine one terminal pair connect in mid position and then the other terminal pair connect for the top position. linking two of the terminals will then give you a 3 terminal 3 position switch

Hope this helps

Best of luck

Bob
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PostPost by: pharriso » Mon May 29, 2017 3:52 pm

Craven wrote:May help
The attachment P1030194.JPG is no longer available


Exactly & here's a picture of the wires on the heater itself:



The white ground normally goes to the dash earth at the chassis connection.
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PostPost by: keith stringer » Wed May 31, 2017 4:23 pm

Thanks everyone who got in touch with suggestions as to the fan wiring problem I had. I got to have another look at it again yesterday and sorted it . What I didn't understand was why their should be a current through the resistor at the same time as the fan receiving 12volts to the fan through the other wire. I thought it should be switched independently one to the other. I know that's how it should be wired according to the diagrams and it works but I feel why run the resistor when there is no need when you could use a different switch to run one or the other independently. Any way enough of that, I put a current down each cable green and yellow and green and black and run a earth wire straight to the battery as suggested. With no joy I then gave the motor a sharp tap with the screw driver and it bust into life. Brushes sticking ? Do you think.
Best regards to all.
Keith
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