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bishbosh
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As you are all aware, last year I moved over to the dark side and replaced my luverly V8 with a stinky (but frugal) 200Tdi.

Unfortunately, the air conditioning wiring system takes information from the V8 ECU which of course is no more. I know it is hard to believe, but I have survived nearly a year and more to the point nearly a whole summer without A/C :P:P .

The situation at present is that when I move the dash control to "dual" or "A/C" I get the right combination of condensor fans and evapoator fans running, but the clutch for the compressor does not engage.

Now this is where it gets tricky, at least for me so pay attention to the ramblings of an electrikery numbnuts: :lol:

I have consulted the workshop manual and discovered the follwoing diagrams:

post-121-1177261698_thumb.jpgpost-121-1177261730_thumb.jpg post-121-1177261754_thumb.jpg

The third image is the Key for the second image.

I have found the connector from the EFI loom (that bit was easy as I remembered undoing it when I took the EFI loom out!)- it is a four pin connector with all the right colour wires to match item 6 (Cable connection to ECU). All good so far.

The pins are

BR +12V from condensor fan motors

BS AC output

YB AC input

WG Fan Relay

The way I have interpreted it is this - The ECU senses 12V from the condensor motors. It then checks that both the pressure switches (21 & 22 on the diag) and that the engine coolant temp (23)are OK before switching the BS pin to earth, thus energising the compressor clutch replay. This stops the A/C working if the engine is too hot or if the A/C pressures are out of range- makes sense. :wacko:

So if I was to put the BS pin to earth, the compressor clutch should engage right? :huh: Only problem is when I do nuffink happens.... :( I don't even get 12V at the compressor so I can't rule out the clutch being knackered yet.... (all came from the donor vehicle so not tested yet...)

The system is currently depressurised, but without the ECU to sense it I can't see how that should stop me engaging the clutch relay by manually earthing the BS PIN.

Can some kind hearted soul please explain what I am doing wrong...?

TIA

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Bish,

Put a 12 v feed and earth to the clutch to make sure it does work :blink: , or you could be looking for a fault that does not exsist ;)

I'm down this coming weekend for the CSW challenge (marshalling), if you can do with out it that long :unsure: I'll happily have a gander ?

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Cheers Les,

I had considered putting 12V to the clutch but didn't want melting wires in my hands! :lol: Did I say I was an electrical numpty?

When are you travelling back from CSW? I could have tea a cakes ready at J21 for you if you fancy a visit...? ;)

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Have you looked at a wiring diagram for the Air con on a 200 Tdi Range Rover as that should show you the wiring required for what you have,

not what you think you should have,

meaning that you can alter it to suit,

rather than trying to get it to work with what you had, when you don't know what you should have...

Make sense :lol:

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Looking at dia 1, theres no input for the ECU to disable anything.

If you have power on fuse 13, then it should run.

I see an A/C input & output on dia 2, but dont see how that connects to dia 1.

Normally the only thing the ECU would need to do is up the revs when a/c is on, thats the input.

suggest you check the clutch as Les suggested.

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Surely in diagram 1 the BS wire needs to go to earth so the relay is energised?

The clutch may well be an issue, but at the moment I can't get juice to it through the loom so there is at least one other problem there too! Will try a direct feed to the clutch tomorrow....

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Can't reaad the diagram cus I opened a bottle of Stolly. After you get the rellay to work the only thing that normally stops the clutch from working is the low pressure switch due to you having an un-pressurised sytem.

jw

<cough> erm yes i missed that connector.

So what normally happens is:

1. you select A/C

2. the ECU ups the revs

3. the ECU allows the clutch to engage

('m not a diesel man, so forgive my ignorance) but if there is no method of increasing the revs &/or it doesnt need it?

So the WG line is on (AC selected) it grounds the BS line.

BR must confirm the fans are runing, you could ignore that i think.

The YB (BY from 12) controls the temperature. Since i dont see an LP valve, it must be done with the clutch.

It may be that the BY output from 12 goes to ground to reduce temp (confirm that) if so simply link YB to BS. If not use a relay to invert. (in fact it might be best to use one anyway, in case current cant be driven from 12.

(21 & 22 only allow this if pressures are correct)

disclaimer - this is all guesswork based on the diagrams. I have elctrrical & refidgeration experinece, but never worked on a LR system.

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Guest diesel_jim
<cough> erm yes i missed that connector.

So what normally happens is:

1. you select A/C

2. the ECU ups the revs

3. the ECU allows the clutch to engage

('m not a diesel man, so forgive my ignorance) but if there is no method of increasing the revs &/or it doesnt need it?

So the WG line is on (AC selected) it grounds the BS line.

.

I think that's right, the V8 needs extra oomph at idle so as not to freak out and stall, unlike a manly chest beating diesel that'll continue on regardless.

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OK, let's break this down a bit.

From my understanding of the wiring diagram, if I put BS to ground the relay should close and the clutch operate. None of the other bits affect it.

Is this statement correct?

It looks like it yes. That would be a good first test, but it will leave the compressor on full time.

I think its by switching the clutch that temperature contol is done. so i think you need to link YB to BS directly or with a relay to get full function.

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I think in the final set up I will need two relays, each switching the BS line. One fed by the engine coolant temp and one fed by the pressure switches.

Of course, getting the bluddy clutch to work is the first thing. I am beginning to suspect a dodgy relay, but I haven't a clue where it is..... :angry:

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Cheers Ralph.

By left, I presume you mean left when sat in the drivers seat? i.e. near side on a RHD vehicle?

If so, then no dice - only one relay under there with totally different wires in it. I think there were more than four too.... :angry::angry:

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