Fan overide switch (the saga continues)

[D2BBA]

Hi Folks,

You may remember that the fans on my FD wont work with the engine on yet they work at 95o with the ignition on position 2.  And this is causing a potetial overheat.  

I have fixed a leeky expansion tank and fitted a new alu AST and I replaced the thermostat to hep with the cooling.  I\'ve had a look with an auto electrician to fit a fan overide switch.

The problem is the guide i\'m using notes that you should check the wires with a voltmeter before splicing into them. If they have voltage on them under any circumstances (ignition on, off, etc.) then you have the wrong wires (as there are large, high current wires in that same harness that you don\'t want to mess with).  We have confirmed they are the corect wires (same colours and definately not the high voltage ones) but they still carry a low residual current.  I\'m dubious about splicing into them incase this damages the ECU.

http://rx7.voodoobox.net/howto/fanswitch/fanswitch.html

Has any one else come up against this?  Or is it possible to just hard wire to the fans do you think, or should I be looking deeper into what the problem may be?

Any help you can offer would be most appreciated!

Cheers
Chris Dobson

[andrewrx7]

Can\'t help with your specific problem, but on my previous FD, I wired a timer and switch into the fans. This allowed me to turn the fans on whenever I wanted, and for however long I wanted. It was independant from the ecu etc, so were not temperature activated. You could say they were paranoia activated! Basically never had any problem with that system. I just studied the FD wiring diagram in the workshop manual - took a bit of time to plan it properly i.e. not to cut into or splice into any wrong wires, but the way I did it, everything worked fine. At the end of the day, even if it didn\'t do anything useful, it at least gave me piece of mind!

Good luck!

[D2BBA]

Top advice there mate!

Do you think it would be worth just buying an HKS or similar fan controller.  I\'ve looked at this before and feedback response was good.  The only probs was it costs £130 and the overide would have been free (would have used the work based auto electrician!).

Give me your thoughts please
Chris

[andrewrx7]

I did my bit of wiring when I had alot less knowledge of what products were on the market for the 7. I actually bought a programmable timer, relays and switch as individual components and wired them up. With that in mind, I have no knowledge of professional fan controllers, so I think it would be wrong of me to suggest any advice or opinion, as to whats best etc. All my parts, I seem to remember, came in at about £50. If I were to fit a fan override again, I think I would go for a professional kit, esp at those kind of prices you mention.

But all this doesn\'t get to the route of your problem. I\'d still be looking for the reason why the fans aren\'t working correctly.

HTH!

[D2BBA]

But all this doesn\'t get to the route of your problem. I\'d still be looking for the reason why the fans aren\'t working correctly.

HTH!

Hmm,

You\'re right mate.  I\'m in a bit of a catch 22 here though.  Its either the GReddy gauge that aint right (seems to creep up even when the Mazda temp gauge stays on mid-way) or something in the fan system (fans not comming on).  I just dont know how to tell which is which, or even how to diagnose what could be wrong with the fan circuit.  It deff aint the solenoids as i\'ve removed each and tested them.

Maybe I should find another auto electrican and just hand over the car for a while!?

Cheers for the input so far!
Chris

[andrewrx7]

Guess you could hand it over to someone you trust with car electrics and just let them sort it.

You could spend a bit of time checking the FD wiring diagram, and see whether the fans and relays are supplied by the same positive feeds and earths if you are on ignition 2 (engine not running) compared to with the engine running. i.e. are there different circuits used depending on whether the car is in ignition2 or running?

You know the fans work, you\'ve said previously about ignition pos. 2, and you say you\'ve checked the relays. If the fans are running at any point, then the ecu must be picking up data from the sensors and switching them on. Therefore fans/sensors/ecu must be working ok? With the car cold, and you turn the ignition on, do the fans stay off - (i.e. sensor/ecu saying don\'t turn the fans on, \'cos the car is cold)? If thats the case, then it does indeed sound like an iffy wire/connection somewhere - just need to trace it! (Just!  :rolleyes:  Not a word you use on an FD!)

[D2BBA]

Howdy guv,

Yep with ignition only on the fans stay off.  They are only on at operating  temp.  Nothing is on when cold, just via the AC button (fans on low).

May be time to visit my local auto electrician and talk them thro with it.  Problem is when people see the car they tend to panick and not want the work...WTF is that etc etc.

Cheers for all the help tho guv!!
Chris

[D2BBA]

Just to let you guys know the problem is sorted now (ish)!!!

Found some really good FAQs on the \'net explaining how to test each part of the coolant electrical system.  Dropped off with local aotu electrician, who confirmed that the ECU is the weak link.  Everything else works fine.

Instead of forking out for a new ECU i\'m fitting an overide switch as a temporary measure, then saving for the Power FC.

http://www.fd3s.net/fan_test.html

Hope this helps anyone in future.

Ta
Chris