405 MI16 Electrical Gremlins
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  1. #1
    Tadpole Naything's Avatar
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    Default 405 MI16 Electrical Gremlins

    Hi, Recently instead of my air-con just working whenever it felt like it, I have completle lost all power to the interior cooling system! No Fans at all, no a/c, not even the light on the a/c on off button. The dash clock still works although it still resets it's self randomly and i have noticed if i turn on the hazard lights the power is drained from the clock in a couple of seconds.

    Now i know these cars have a reputation for bad wiring, connections and earths but could anyone point me in the direction i should be looking? I have made sure the battery negative lead is firm (though i think the battery might be on it's way out), i have also noticed the previous owner has tried to repair the earth loop caused by the taillights but instead of connecting the tailights to a new earth, they just soldered a wire from the taillights to the original earth wire which seemed a bit pointless to me. Should i try and find a new earth for those?

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    Any suggestions greatly appreciated.

  2. #2
    Fellow Frogger!
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    Default .

    Check fuse number 18.
    1984 505 STI

  3. #3
    Tadpole Naything's Avatar
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    Quote Originally Posted by lunchcutter
    Check fuse number 18.

    Thanks, i forgot to mention i checked all the fuses as well. I just went and double checked to be sure, and while they were still all ok i noticed since disconecting the CD player to have a look around inside the dash that the dash clock is a lot brighter and willl no longer be drained by the hazard light switch. Do you think who ever took out the Factory head unit migh have had to dodgy up the wiring for some reason? Which may be causing my problems?

  4. #4
    Fellow Frogger!
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    Default .

    Definitely sounds a bit dodgy, you don't want your CD player drawing amps from the general 12V lines which power all your instruments etc. If in doubt probably best to run separate power and earth lines from the battery through the firewall somewhere behind the glovebox and into the area behind the head unit.
    1984 505 STI

  5. #5
    Tadpole Naything's Avatar
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    Yeah i'll try that, does any one know what length of wire i will need to do that comfortably? I still have a feeling the fan problem is caused by something else though, no one else has had a similar problem?

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    They have a similar problem on the Xantia caused by voltage drop through the ignition switch.
    The common fix is to remove the wire from the ignition switch and connect it to the power to the cigar lighter which has stronger wiring.
    Don't know if yours has a similar set up, but worth a look.

    Here's a link to all the info you'll need to fix it on a Xantia so hope it will make sense on a Pug.

    http://www.frenchcarforum.co.uk/foru...ic.php?t=17322



    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

  7. #7
    Tadpole Naything's Avatar
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    Thanks Alan, I now have the center console out and the steering column un covered. I only had a quick look around as i have to start getting ready for work. There only seems to be 4 wires going into the ignition not 6 as in the ftench car forum though i didn't get upside down to have a proper look. The red wire ("Brown plug MR wire 1: Unfused permanent 12V from battery. " if it's the same as in the citreon) already had a section striped back with a bit of solder on it (it was wrapped in electrical tape) as if someone had tried this before. The wire going to the cigarette lighter is about 1/8 the size of any of these wires so i'm not sure it could handle the power needed. The advice on the forum you linked me to seems to point towards installing a relay in to the circuit to take the load off of the ignition switch. So i might look into that tomorrow. But for now i'm off to work, Thanks for the advice.

  8. #8
    Fellow Frogger!
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    Default No fan

    I had the same problem (no fan) a few weeks ago. Not your other gremlins though!
    In my case it was a relay that lives under the dash/steering binnacle. It had burned out. A $6 relay and $4 connector block. One and a half hour's work.
    At $80 per hr!

  9. #9
    Tadpole Naything's Avatar
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    Default Uh Oh

    Well i got a late start looking at the problem today, but after trying to bypass the ignition switch and still getting no power to any part of the temprature control panel, i decided to investigate the actual wiring and connectors. Thats when i found the dreaded coolant leak! It doesn't seem like there's a lot leaking there, the carpet is only just barely damp, but it does have plainly visible drops of coolant forming on the outside of the fan housing. So i'm thinking the leaking coolant could be responsible for these problems as well as a symptom of a leaky hose, or worse a stuffed matrix. Oh well i've been looking for an excuse to take the dash apart and try and muffle some of those rattles!

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    Tadpole Naything's Avatar
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    Well i think i've located the source of the problem, it was realted to fuse 18 (and 15) as lunchcutter suggested, it wasn't blown it couldn't be, it wasn't getting any power at all! Which made me think it was the relay, but after swapping it with the same sort of relay and not getting any different result aswell as the fact that the rear heater switch has been getting power the whole time has led me to believe there is something going on in the circuits in the fuse box itself. I'm basing this mainly on the fact that all the wires that are supposed to be delivering current to it are doing so but yet there is no power getting to those 2 fuses, as well as the fact it seems to have hemorrhaged a lot of green liquid as i mentioned in this post So where do i find all these 'bad earths' ? . So i'm going to replace the fuseboard and hope for the best at this stage, if this doesn't fix it it could turn into a big job.

  11. #11
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    I replaced the fuse board today to no effect, what i did discover was that i do get power to the a/c switch just not enough to be of any use. I accidentally left the blower motor unplugged when i was trying to test the system and noticed that the light in the a/c switch was giving off a faint glow! There wasn't even enough power getting to it to light up my 12v circuit tester but it was definitely on. As soon as i plugged the fan back in however it was gone again. Excuse my lack of knowledge but what could be stopping the full amount of power from getting through?

  12. #12
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    Try bypassing the wire from the fuse box to the A/C switch - I usually use a length of wire with an alligator clip at each end for this sort of thing. If you have known good power to the switch and it still doesnt work look for a faulty earth. All that nasty green corrosive water may have corroded the wires on the inside or any contacts or connectors out of sight. Even use another known good voltage source to confirm the problem. Even a wire with its own fuse straight from the battery. If it wont work with that you know the problem is on the earth side of the circuit!

  13. #13
    Tadpole Naything's Avatar
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    Thank you Paul! I tried you suggestion by running a wire from the battery to the the no. 18 fuse and the fans started up, then i took the wire off and they kept going and have continued to do start up with the igntition since. Can circuits forget what they are supposed to do and need a gentle reminder every now and then?

  14. #14
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    Default .

    I wouldn't have thought that a 'reminder' could fix a problem as you described. Seems weird. Is it possible that you disturbed a connection back into working properly while you were running this battery test? Also a note on fuses, sometimes the fuse can be ok but the things which hold it firm have broken so that it is loose in its socket. I have a fuse like this on my 505.
    1984 505 STI

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