Hi there, I recently bought a roadster that has its cooling fan wired to a switch which allows you to manually turn the cooling fan on and off. I would like to remove this setup and have the fan turn on normally as the car gets to temp. In place of the fan relay that’s meant to be in fuse box there is two spade connectors which run to a relay/switch box with a ground running off. The wires then run from the relay/switch box through the firewall into the foot-well where there connected to the manual interior switch. As you can see in the pictures a red wired with an inline fuse is also connected to the manual switch. I bought an LA10 relay for the cooling fan, what is the purpose of the red wire with the line fuse? Any help would be appreciated, Thanks!
The point of a relay is to indirectly manage the main power to an item. This protects switches, gauges, instruments, etc from the higher power needed to operate fans, heaters. lights, etc.
on that basis have no clue as to why the inline fuse on the switch wire as the main current for the fan should come straight off the relay. Perhaps the switch has been put on the main relay to fan power cable rather than the temperature sensor feed?
I would try to speak to the previous owner to find out why he went to this effort. Can only guess that the sensor controlling the fan was faulty and it ran all the time or perhaps not at all.
As you say normal setup is LA10 in fusebox and fuse protected circuit to fan but some effort made to change this so unlikely to be a case of remove switch. non standard relay and wiring, reinstate LA10 and all sorted.
Personally electrics is not something I would play about with - go to an auto electrician would be my advice.
I’d an Audi 80 Sport a few years ago saw 2 unplugged connectors that looked like they should be joined - I blew two relays, knocked out lights, indicators & horn, luckily it cost £25 for 2 new relays & no permanent damage was done !
An uncle who’s an electrician said to me before about electricity “you can’t see it or hear it & you might only feel it once” something I pay great heed to
My guess would be that the red wire with the in line fuse has been spliced into either a permanent live or a switched live ( comes on when ignition is switched on ). By live I mean 12 volts. This is then passed through the switch, and when turned on, passes 12 volts to the relay, the other side of which is grounded on the bolt holding it to the bodywork. This means you are switching the 12 volts rather than the normal way of doing it where the relay has 12 volts going to it and the earth ( ground ) side is switched. The thing that isn’t clear from the photos is there seems to be two wires running from the relay to the switch. Is the switch illuminated when it is switched on? If it is this second wire may be the ground for the lamp in the switch. Note: if you intend keeping this setup, which I wouldn’t recommend as switching the live 12 volts is a bad plan, you should add a diode across the relay to prevent the switch contacts burning out due to the voltage spike generated in the relay coil by the voltage collapsing. If it were me I’d be tempted to remove the two wires going to the relay socket and plug your LA10 relay in and see what happens. I am not recommending this, just saying that’s what I’d try, but I am a electronics engineer so maybe that makes me a bit more casual about these things. You don’t say what model or year you car is so I’m not sure where the signal to energise the relay comes from. If you post the info I’ll take a look if you like. If you could find out why this modification was carried out by the previous owner that would help, ie was it done because the normal switching circuit had failed or did they just want a manual override?
This is normally a track day mod, to allow cooling while not running the engine (after high temperature reached during time on track.) Question really is does the fan work normally while the engine is running?
If not, then the mod is wrong. It could also mean - as Rhino suggests, that the normal run mode is faulty - usually the temperature switch (temp dependant resistor) on the engine. Run the engine and see if the fan works with the switch off, if it doesn’t work then the temp switch is faulty, or there’s another fault somewhere.
I did the track day mod on a couple of local cars, neither of which I’m aware have been sold. That doesn’t mean that someone else has gone the same route, as it makes sense to me.
Quote from Gerry " Run the engine and see if the fan works with the switch off, if it doesn’t work then the temp switch is faulty, or there’s another fault somewhere. " I think with the original fan relay missing the fan will not run without the switch being on. Without the relay in place even if the correct signal is there, there is no relay to turn the fan on. The only way to find out is put your new relay in. As I said that’s what I would try but I fully understand the caution voiced by others. D
Point taken, I quickly read the OP’s post and missed the point the fan relay was missing from it’s normal position. However I stick by my assumption is was a track day mod, just done incorrectly. I also know this was not done by me, as the connectors I use are different to those illustrated.
Another thought - The original wiring appears to be still in place, just the relay is missing - yes? I’d stick the relay back in and try with the engine running, and the dash switch OFF - if the fan still works when the engine temp reaches it’s normal point, when if everything else is O/K - then the fan should still work. If it doesn’t ten you may need a new temperature detector - or a wiring check.
The switched added relay coil and contact is wired to battery live (next to the key switch*) so it can power up the fan when the ignition is off (Trackday cooling mode) and the added relay appears to bridge the normal (missing) fan relay contacts ) so in my book both ways should work if you put the original relay back in. If you don’t intend to do any trackdays, then by all means remove the dash switch and the associated wiring between battery live and added relay, including the bridging (red) wires back to the proper relay base. If it were me, I’d stick a 10 amp fuse in the live lead from the keyswitch* lead, otherwise the battery isn’t protected, if you intend to keep the mod.
I assume the red connected to the thick blue wire is steering column wiring? - it’s hard to tell. Most NA’s I’ve worked on have white main wires to the keyswitch.
Check both ways work if you wish to keep the mod wiring. BUT - always switch the dash switch off when running the engine, or you’ll get extra cooling when it’s not needed! - Longer heat up time. I’ve wired a warning light in circuit to warn when the track cooling switch is on - it’s a good reminder.
Thanks for the help so far guys, the car is an Eunos Roadster 1993 1.8. I would like it back to stock really, I would rather have it turn on automatically than trying to remember to switch it on. I started the car and ran it with the stock cooling fan relay installed in the fuse box and had the interior fan switch turned off. When the car hit half way on the temp gauge the fan didn’t turn on. It also doesnt come on if you remove the relay from the fuse box. How would I need a new thermoswitch (which i’m guessing is the green sensor at the back of the engine under the coilpack?) when I get a reading on the temp gauge?
Yes the red connected to the blue wire is in the footwell, is the red wire not “stock”? Is there only meant to be the single blue wire running into that yellow/white bit of plastic?
Below is some more detailed pictures showing the DIY relay circuit in the engine bay next to the fuse box. Also you can see the two wires that run from the fuse box to the relay/switch then the other twos that run through the firewall. As you can see the ground coming off one of the wires.
In ‘normal’ mode, the fan runs when it needs to, as the temp sensor sees fit, unlike older cars when the fan is driven by a drive belt from the main crank. The aim is to prevent overheating, rather than constant cooling.
If you would rather keep it ‘stock’, then remove all the mod wiring, relay and ground connection to the relay and the dash switch - though you may need to find a bung or cap of some sort to plug the hole where the switch was. If the switch is a normal Mazda type, then you may need a blanking plate to cover the aperture.Where the red wire connects to the blue, you need to cut this off close to the connector, and tape the live end up with electrical tape (Halfords) unless you can undo the connector and remove the red wire completely? - You’ll still need the connector I suspect, as the blue wire may have been cut to make the joint.
From what you’ve said, the normal wiring seems to be intact, so you just need the relay plugged into the fuse box socket for happy motoring. Enjoy! If there’s still a problem, PM me and and I’ll reply.
The wiring for the cooling fan must be OK because with the LA10 relay in the fuse box, when the TFA and GND terminal are bridged in diagnostic box (which I just found out you could do ) you can hear the LA10 relay click and the cooling fan turns on. However the cooling fan doesn’t actually turn on its self even when the car has been idling from a cold start for 15mins, the thermostat opens around the 10 min mark. I pretty sure I could start to hear the water boiling so I just turned it off. I have bought a new thermoswitch to see if that is the issue.
Back to the DIY wiring, if the thermoswitch is the issue and the fan starts to work automatically I will then remove the manual switch wiring which will be simple. The only bit I’m unsure about is the red (12v power) wire with the inline fuse that appears to be spliced into the blue wire. In the pictures I posted above you can see the fitting used to connect the two wires together, you can un-clip the top face and it swing back and there appears to be a mental piece that has been pressed in to puncture the plastic on both wires connecting them. However it doesn’t seem easy to disconnect, I could properly get the metal piece out using a pick/small screwdriver and the connector would come apart. But I don’t want to damage the blue wire so ill most likely just leave it be and cut the red wire shorter and tape it up. Unless someone is familiar with that style of connector and can explain how to remove them, Iv never seen it before… It would be great to know however what the blue wire is thats been connected to, I believe its a “Switched live” as the switch only works when the ignition is on and not a permanent live (eg constantly powered by the battery?)
Ill let yous know if the thermoswitch fixes it, thanks
I have just done a bit of googling, the connector used is a “run and tap” connector. It looks very similar to the top left connector and is of a similar colour. By the looks of it the blue wire will have been weakened to much to remove the connector.
Just for your info, I started my 1.8 mk1 this morning, it’s sitting in the garage so I start it now and again just to run it for a bit. It was quite a cold morning. The temperature gauge reached mid possition in about 5 mins and seemed quite stable there ( I was not watching it as doing other things ) it was about half an hour before the fan came on and when I looked the temp gauge was still around the mid possition, maybe a bit higher but not much.
D
In the current ambient temperatures it will take a good while for the fan to kick in as indicated in the post above. I think once again you are not being patient enough and giving up too soon.
The thermoswitch was faulty, I got a replacement in today and now the fan turns on and off itself after the car has been idling for around 20mins. I would have found this a lot sooner but earlier this month when I tried just sticking the LA10 cooling fan relay in the fuse box the gauge passed 1/2 and was nearing 3/4 and the fan didn’t turn on. The car still “overheated” to 3/4 quickly after starting the car from cold on the gauge with the cooling fan manually turned on so I focused on trying to figure what was causing this. I have removed all the DIY wiring from the car apart from the red live wire. I just disconnected it from the interior switch and taped up the male spade connector and secured it up in the dash.
