110 Isuzu Electrical Gremlin

[D3Jon]

The electrical system of my Isuzu 110 County is causing me some strife! You see, here's what happens when you add advanced electrical features like a fan / demister to a car... :D:D

She's a flapless 1990 air-con model complete with 3 speed fan. I have a problem which reared it's ugly head yesterday and has me puzzled.

1) The blower motor has been working intermittently for a while now, but if I slam the front passenger door or open the bonnet and bang the blower motor's casing it generally starts to run. Once running all 3 fan speeds work. I figured it was the motor bushes and have left it alone for the time being. Yesterday I had the usual problem getting the fan to work, but part way through my journey it started working on its own (it was raining so that was a blessing).

2) I got where I was going and the car wouldn't turn off when I turned off the ignition key, so I figured it was the Jideco electric engine stopper as it wasn't making it's usual whirring noise through the bulkhead no matter how many times I turned the key to the off position.

3) I then noticed that even with the key out of the ignition, all of my ignition circuit controlled things were working, for example fuel gauge, temperature gauge, the heater motor, etc. So I started to think it was the ignition key mechanism / barrel itself, but I also noticed that the Volt Meter dropped when I turned the key to off, and went back to normal when the key was in position II, so turning the key to the off position *was* doing something.

4) I popped the bonnet and stopped the engine manually by pulling on diesel injection pumps stop mechanisim. The engine obviously stopped.

5) Back in the cab, I noticed that everything ignition controlled was still ON, gauges, blower, you name it, even though the ignition key was out of the barrel and the engine was now stopped. I turned the blower motor to the off position and everything turned off just like as if I'd turned the ignition off.

6) So now, in true electrical gremlin style everything is back to normal, the car stops normally and everything turns off on the ignition key as it should.

It seems that something is 'back feeding' into the ignition controlled circuit somehow, most likely via the blower motor itself or it's wiring.

I'm at home now, so I'm going to have a good prod and poke, but would welcome any pointers from the more electrically experienced!

Thanks in advance,

Jon

[wovenrovings]

Do you have a wiring diagram? And has the wiring ever been messed with, e.g by someone putting in a new radio?

[EchiDna]

most of the items you mention are run by vacuum based switching in the post 1987 aircon 110 ... so if the vacuum is still present, they can still "switch".

regarding the blower motor, they can get water pooling inside em and this can cause a short, resulting in a bad earth which could easily cause all the problems you mention.
My advice is try looking inside the fan motor for signs of moisture before getting too upset :) of course if this drains away, the gremlin disappears until the next rainstorm!

[D3Jon]

Do you have a wiring diagram? And has the wiring ever been messed with, e.g by someone putting in a new radio?

Hi Wovenrovings,

I've placed a couple of wiring diagrams in the upload section of this site, I had to scan the larger one at a higher resolution, so it's in a compressed zip file.

They're both to be found here: LINK TO WIRING DIAGRAMS (http://www.aulro.com/afvb/local_links.php?catid=3)

The vehicle (like any 18 year old Land Rover) has been messed with a bit, but not too bad. It's got a pair of driving lights, currently the air con compressor is removed, it has a transfer fuel pump from an auxiliary side tank back to the main tank and it's been fitted with an engine immobiliser as per current legislation.

I have no idea how the immobiliser is fitted, but I have seen it behind the dash with a stack of wires coming out of it!

Jon

[Rangier Rover]

Some of your troble sounds like a after market relay holdig on partly polarised and feeding power back. Is the fan earth switching?
Tony

[C H T]

Do you have an electric trailer brake controller fitted? I had a very similar problem many years ago on a Defender - turn the ignition off and nothing happened - the EBC was feeding back into the ignition circuit. Removed the EBC - no more problems - the particular unit was renowned for causing problems.

Christopher

[87County]

did you see this?

http://www.aulro.com/afvb/technical-chatter/50155-county-advice-3-9d-electrical-please.html?highlight=aircon

maybe could be some help - it was for me :)

[D3Jon]

Thanks for all your useful replies. I'm 99% sure I've got this sorted, I'm being nagged to get off the computer by my wife as we've got to go out, so I'll post details later today.

Cheers,

Jon

[Freestyler]

Hi Jon, Just infront of the fan motor is the series resistors that control the speed of you fan, check those connections. the one closes to the fan is the power feed to the fan, it's probably rusty and the terminal would look like it has been hot. I had this problem this week and just fixed it. My trucks a V8 so I don't know the wiring of a isuzu but a mate of mine had the same stopping the engine problem, fitted a universal cable to the stopper solenoid and mounted it on the RHS of the steering column where the later V8s had a choke control. The Gauges staying on would be related to the alternator still going around producing power even though the battery had been disconnected. Stop the engine first the turn the switch off see what happens. I your vehicle a 1990 county? I have only every seen one in this country and my father owns it. Tim

[D3Jon]

Some of your troble sounds like a after market relay holdig on partly polarised and feeding power back. Is the fan earth switching?
Tony


Hi Jon, Just infront of the fan motor is the series resistors that control the speed of you fan, check those connections. the one closes to the fan is the power feed to the fan, it's probably rusty and the terminal would look like it has been hot. I had this problem this week and just fixed it. My trucks a V8 so I don't know the wiring of a isuzu but a mate of mine had the same stopping the engine problem, fitted a universal cable to the stopper solenoid and mounted it on the RHS of the steering column where the later V8s had a choke control. The Gauges staying on would be related to the alternator still going around producing power even though the battery had been disconnected. Stop the engine first the turn the switch off see what happens. I your vehicle a 1990 county? I have only every seen one in this country and my father owns it. Tim

Thanks for theses helpful posts, you were both pretty much bang on fellas, here's what was happening...

One of the connectors within the multi-plug to the blower motor's resistor pack was corroded, additionally the main power connector from the resistor pack to the motor itself was also corroded and had been getting very hot. It had obviously been arcing resulting in the plastic outer insulation melting. I cleaned this lot up and also replaced the damaged connector.

I can't be absolutely sure, but I'm pretty certain that all the arcing going on at the blower motor connectors caused either the main ignition relay or the relay in the cars immobiliser to stick on, probably due to arcing across the relays contacts. All is OK now.

Thanks again,

Jon