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Evening all

My compressor has been running excessive lately and iv struggled to track down a leak. Tonight the compressor burnt out and was too hot too touch.

When unplugging the compressor the top left pin. Looking towards the front of the car had melted.

Fortunately I had another compressor which had been rebuilt and I knew it was a runner.

I swapped the compressor out with the aid of some oven gloves and repaired the melted terminals.

Even after resetting the eas fault using the dongle.

I can't get power to the compressor.

Tried all the pins with a multi meter but can't pick anything up.

Is there any fuses further down the line where I should be looking.

Any pointers much appreciated

Dan

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You obviously have checked the fuse boxes haven't you

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Check between the Orange and Black wires, they should be shorted together inside the pump. If they are open circuit, that means the thermal cutout has tripped and not untripped when it cooled down. If that is the case the ECU doesn't try to turn it on.

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Morning Gents

Symes, i did go through the fuse box and tested the fuses, all checked ok. But i agree it is a question that is worth asking 😀

I have found that i do have 12 V to the compressor. But it is not running.

I will go and check the thermal cut out. I believe i saw the video on the RSW website this morning whilst doing some homework

If the thermal cut out is faulty, is there a way to bypass, to prove the pump does run ?

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To bypass the thermal switch read Richard’s post directly above yours. Short the orange and black wires.

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Hi when you say short between them

Do that on the pump side of the multi plug or the vehicle side of the multi plug

Iv gone over checking fuses and whilst its all connected is short on Relay 20 between pin 5 and 3

All i get from the pump area is 1 solid click and nothing else

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I also tested between the pins for the thermal cut out on the multi plug for the pump and it was a closed circuit, no resistance.

So i assume that the thermal contact is in one piece and working as it should

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Shorting on the pump side only would have little effect as the ECU needs see the closed circuit before switching the pump on. If it’s closed circuit on the pump side already then you can assume the thermal cut out is working.

You say you have 12V at the compressor so it has effectively been turned on by the ECU! How did you check this because if you break the connector the ECU won’t provide the 12V (because the thermal cut out signal will go open circuit to the ECU). Have you checked the earth/ground is also OK on the vehicle loom side of the connector?

I would be tempted to just apply 12V directly across the compressor motor, +12V on pin 4 (purple/light green) and an earth/ground on pin 3 (black) and see if the compressor motor actually runs. If not, then the compressor is at fault and needs refurbishing (new brushes?) or replacement. If it does run then check the vehicle side of the earth/ground on pin 3.

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Thanks Garvin and i will get on to these tips tonight

I found i had 12v going to the compressor by losing my temper and pushing a multimeter probe into the cable on the pump side of the multi plug

I will try grounding as you say

But i feel the conclusion maybe that the back up is or never was any good.

Thank you all for the advice ( as always) and i will report back with any findings

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With the compressor unplugged, the wire colours are different. It's have a Green, an Orange and a Black. Put positive 12V from a battery on the Green and negative to the Black. Use a battery rather than a power supply as it draws about 10A with no load and can trip out my 15A bench supply with a finger over the output when checking for pressure.

As said, if the thermal switch is dead, a jumper wire between Orange and Black (on either the compressor or wiring loom side of the plug) will fool the ECU into thinking it is good but if you have continuity between the two wires (with the compressor unplugged), it is fine.

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Its me again

Big thank you to you all.

Im not electrically biased as such. Iv always been and worked on the mechanical side of life

Your problem solving checked out the dead compressor and also the spare

Electrically I found the spare had a failed thermal switch. The current pump with the burnt out 12V feed did not

After following all the tests i decided to break down the current frazzled pump, what do i have to lose

I found the bushes on the spare to be in a much better state than the current so i swapped them over. I then also discover that the current pump has a seized bearing on the piston arm. Bingo

I imagine thats enough to melt something and also when jumping pin 5 and 3 on Relay 20, explains the audible click. not a relay but the actual pump trying to move

I will hold my hand up and say even though i had a spare seal to replace on the piston. I just dont have the nack in swapping them. I can cut the old one off, but im dire and refitting

So i split the piston arm away from the knackered bearing and replaced it on to the bearing coming from the spare pump.

Reason i did this is that the spare pump has a very worn piston seal and liner with scoring, so it made sense in my strange mind to re use the bearing instead.

Result, i now have a solid working pump. I do feel it runs too often. I changed the seals in the block. Re sprayed all the bags and connections yesterday also. Still feel like its leaking somewhere

Thanks again for the tips. Certainly learnt some new lessons and it also allowed me to make it to the Lincolnshire aviation museum yesterday to watch some tanks and planes feed the senses

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I’m glad you got it working.
Does anyone know if the parts (eg bearings etc) to rebuild a pump are available? (I know where to get seals). I have a spare pump that needs more than seals to make it a functional spare.