Kenlow fan wiring

[Dave S]

Good afternoon, can I lean on the collective’s knowledge?

My car (which I have had for 1 year now) came with a kenlow fan installed. When out in the hot period last year the fan came on and fuse 3/4 blew (fan came on because viscous coupling needs replacing). There was also evidence of heat damage to the fuse carried board. On investigation I discovered that the fan was drawing power directly from fuse 3/4 even though there was a relay present in the circuitry. Over the winter I have replaced the fuse box and rewired the kenlow as the attached kenlow wiring diagram. This takes a feed direct from the battery to a fused relay. This works fine for the override switch, however the fuse blows (in the fuse box on the low current side of the circuit) when the Kenlow thermostatic switch activates.

If I wire it so that either only the override switch or the Kenlow thermostatic switch are used to trigger the fan all is well. As a result there is not an issue with the individual components. My thought is that in providing power to both sides of the Kenlow thermostatic switch it is creating a short circuit and that the override switch present is not the 'special' KLM0570 switch noted on the kenlow wiring diagram attached.

Does anyone have any observations/thoughts/ideas in this regard?

My thoughts to resolve this is to provide two relays, one as a trigger from the Thermostatic switch and the second as a trigger from the override switch. This looks OK to me, but I am not an electrician. Does anyone see any issue with this proposal as the 2 relay wiring diagram attached 2 relay wiring.pdf ?

Thanks

[DZP]

Hi Dave,
I would say that there is a good chance that your manual override switch is the problem, if this is not the Kenlowe Off/Auto/On switch.
It sound like it is connecting the thermocouple output to earth when in the off position (which is bad!!), whist providing 12v to the relay when on.
(e.g. you have the connection from the thermocouple on the common pin of the manual switch).
If you can provide information of the manual switch and pin-out connections being used, then I might be able to advise further.
Regards,
Den

[Dave S]

Hi Den. Thanks for your response. The manual override switch is on or off only, it does not have an auto position. I have a couple of pictures. Not really much help as the label on the switch is pretty much unreadable. Can just about make out supply which is connected to the fuse box. The middle connection returns to the thermostatic switch and the other connection goes to earth.

[Wheelz]

It appears to me that the earth connection shown on the switch could be causing the short - as it warns on the diagram - if the wrong type of switch is used.

[StagJonno]

Some Kenlowe fans were 2-speed, identified by 3 wires from the fan itself. If the high speed wire is energised without the low speed wire, it will draw a massive current and blow the fuse.

[Dave S]

No, there are only two wires coming from the fan.

[wilf]

Some Kenlowe fans were 2-speed, identified by 3 wires from the fan itself. If the high speed wire is energised without the low speed wire, it will draw a massive current and blow the fuse.

Very true - mine needed a 60A fuse to avoid that - necessary as the over-ride goes straight to the second (high) speed.

[DZP]

Hi Dave,
Disconnect the earth connection from the switch.
The switch warning lamp will probably stop working, but I suspect manual override and thermocouple will both operate OK.
Den

[Dave S]

Cheers. I will give that a go at the weekend. May have to invest in some more fuses.

[Dave S]

Hi All, taking comments from the replies to my query into consideration I have resolved my Kenlow wiring issues.

in case anyone is interested, I removed the existing illuminated override switch and replaced it with an on-off-on switch and a separate illuminated warning light wired as the attached diagram. This means I get a warning light when the fan is triggered either by the thermostatic switch or when in the overide position. So spent most of the day upside down under the dashboard as this needed two new wires run from the relay mounted near the radiator to the switch under the dashboard by the steering wheel.

[022Dave]

Hello Dave,

I had to fit a diode into the lamp circuit to stop it glowing at speed; the Kenlowe was acting as a generator.

Another Dave

[DJT]

Hello Dave,

I had to fit a diode into the lamp circuit to stop it glowing at speed; the Kenlowe was acting as a generator.

Another Dave

Likewise. Anything above 50mph and the LED illuminated due to the fan being rotated by air movement through the radiator. A diode sorted that.

Dave 3

[Dave S]

Thanks Daves (great name by the way) Diodes is a bit beyond my electrical knowledge. Can you give a bit more info on the diode spec and where to install in the circuit. Cheers

[DJT]

What you need is a Zener diode in series with the warning lamp. This will block electrical flow to the lamp from the freewheeling fan, but will allow the full 12v when the fan is switched on. Sorry, but I cannot find details of the diode I used.

Edit: just done a forum search on Zener and came up with a couple of old threads. It seems it was a 8.2v Zener Diode bought from Maplins, who no longer exist. I am sure a quick search online will find something similar.

[Stag About Town]

When I bought my Kenlowe I told them I only wanted manual control so they sent instructions. It is a 2 speed but only operates on one. Attached PDF if of any use. I know virtually nothing about the electrics but this seems to work OK. John Kenlowe Wiring (1).pdf