Electrictian advice needed with A/C

[gmeddy]

help is needed with my A/C, 200tdi, (no control box under bonnet or under passenger seat.)

It's stopped working with these symptoms:
Compressor kicks in and works on fan stages one and two but fan does not work.
Compressos does not kick in on fan stage three but fan does run at full speed.

here's the switch

http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs498.ash2/77147_465019888743_733373743_5549747_5812865_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs965.snc4/75839_465019523743_733373743_5549743_7383514_n.jpg

if you number the blades clockwise from top left 1. 2. 3. 4.
Number 2 has connection with one of the other three in each of the fan speed settings.
connections are as follows:
stage one: 1-2
stage two: 2-3
stage three: 2-4

there is no connection between any of them when fan is off.

when A/C nob is turned up, connection between the top yellow cable is on through all fan speed settings - thats the A/C control.

So looks like the switch is working fine?

with my test light, testing in car with motor running, i only got a light up on number 4, only when fan was not running.
when fan ran on stage three, the light would go out on that one wire and i could not get a light up on any of the other wires.

this is interesting seing as number 4 is the one that unites with 2 when fan is on stage 3.

so now i'm guessing there is some control box/relay under the dash somewhere in the A/C unit that the wires from the switch run to, and it's that unit that is malfunctioning.


is there anyone who has dealt with this system of wireing before?

I've read that on some defenders, maybe 300tdi? the control for A/C is under the passenger seat, but on mine there is only a + wire which is constantly on to a relay, (which does not seem to be doing anything because it's always kicked in, instead of having ignition power switch it on and off) and when disconnected the fan and A/C do not work at all.

[bee utey]

Start I think with finding the fan speed resistor. You should find it somewhere in the cool air stream. They do break, regularly.

[fraser130]

I notice the thing that the 2 yellow wires go to is a potentiometer, this means there must be an electronic control circuit somewhere too, as they cannot carry any usable current without burning out.
Most likely it adjusts the cabin temperature, so the control box (somwhere) will control the compressor.

Sorry I can't help more.
Fraser

[gmeddy]

i hate the people who designed this A/C system. :censored:

the wires go down behind the fan motor and condenser! access is prevented by the metal grill plate in front of passenger feet.

the two bolts holding it to the floor wont budge, one is a flat blade screw driver head and another is a 10mm nut head, the screw driver head is seized and wont even turn with an impact driver and the nut head turns, spinning the nut on the other side.
there is no access to the other side of these bolts. :wallbash:
i'm stuck.

the other possibility that i'd really hope for is that one of the relay looking boxes bolted to the back of the fuse holder frame in the centre in front of the gear stick could be the controller.
but there is a few there and i cant see where all their wires go.

the only relay under the bonnet i could find and had hoped was the A/C control, turned out to just be the pre-heater coil for engine start.

it's getting over 40 up here, need A/C!! :BigCry:

[fraser130]

Just to be sure, you do know that the switch you have in the photo should have 2 knobs?
one (long skinny one) is a 3 setting switch (fan speed maybe), the other (the short sleeve) is a variable control (temp maybe)

So it is two seperate controls in one.

Fraser

[slug_burner]

i hate the people who designed this A/C system. :censored:

the wires go down behind the fan motor and condenser! access is prevented by the metal grill plate in front of passenger feet.

the two bolts holding it to the floor wont budge, one is a flat blade screw driver head and another is a 10mm nut head, the screw driver head is seized and wont even turn with an impact driver and the nut head turns, spinning the nut on the other side.
there is no access to the other side of these bolts. :wallbash:
i'm stuck.

the other possibility that i'd really hope for is that one of the relay looking boxes bolted to the back of the fuse holder frame in the centre in front of the gear stick could be the controller.
but there is a few there and i cant see where all their wires go.

the only relay under the bonnet i could find and had hoped was the A/C control, turned out to just be the pre-heater coil for engine start.

it's getting over 40 up here, need A/C!! :BigCry:

Are you able to control the compressor and other individual parts directly? Maybe you can bypass the current suspect control system if you can force the compressor clutch and fan controls.

I think a circuit diagram could be very handy to try and sort this out. Have you got one? There is a couple of reference CDs that will contain the info you need in the shop associated with this web site

[bee utey]

Are you able to control the compressor and other individual parts directly? Maybe you can bypass the current suspect control system if you can force the compressor clutch and fan controls.

I think a circuit diagram could be very handy to try and sort this out. Have you got one? There is a couple of reference CDs that will contain the info you need in the shop associated with this web site

In essence I agree here, however if you visit an a/c repairer or a wrecker, get a thermostat off an under dash unit and wire that into the replacement compressor feed wire. The thermostat will have a pipe that needs to be close to/into the evaporator core. Any old under dash unit will have one you can steal. No electronics needed.

[p38arover]

I don't know if this is the same AC unit or if this is from the later Defender:

https://www.aulro.com/afvb/images/imported/2015/09/763.jpg

[gmeddy]

I dont seem to have much stuff at all under my passenger seat but the battery and one relay that is just wired up to be always on, and when that is disconnected the fan and AC don't work at all.
other than that, all the other things in that diagram that are supposed to be in the battery compartment could be anywhere for all i know.

I never got into the condenser area for the reasons i already mentioned, and i never got around to finding a solution (like drilling holes from under the floor in search of the bolt heads) because the other day on a long hot (43 degrees!!) drive to Wyndham and back, we turned it on and by some miracle it started working again!

So I'll re-visit this thread if and when it fails again. Finger's Crossed! ;)