Airconditioning thermostat - burdon type - fix or replace?

Quote:

---

Originally Posted by scarry

You need to bridge the wires out,then do same for pressure switch on drier or pipework under bonnet.

Its a process of elimination,unless you have a multimeter.

---

I find it hard to be clear because sometimes I don't know what the parts are called. I have bridged the high pressure switch (the one that looks like a cooler probe) on the pipe work in the engine bay and there was no power - the compressor didn't fire up.

The only thing in the system I haven't checked though (just realised) is the pressure switch on the drier. I'll have a look at that sometime today.

Thanks everyone for your help.


EDIT - and I have a good multi meter. Just don't know how to use it [emoji23]

Do the electric fan(s) come on when turning aircond on? mine has 2 fans.

If so, as a short term fix, if you need the vehicle. Do the jump wire trick to compressor and run it through a switch inside.
Turn it on/off manually.

Never done it, so no idea if it could cause harm to other components.

Ps. the pressure switch is to protect the compressor, so that could be a problem if bypassing.
others may know more.

Cheers Ronski. Might be a good idea. I'll have a think about that. I don't know if the air con cooling fans come on the front mounted condenser. Will also have to check that. The blower fan inside comes on no worries so there is no issue there.

So have a copy of the rave manual now. I have checked the following:
1. Compressor - jumped the compressor from the battery and it fired right up and put out cold air
2. High/low pressure switch (on pipework in engine bay) - bridged the switch and the compressor did not fire up. There is no power in the black-green wire coming in to the plug. This obviously feeds the compressor too.
3. Internal switch - the A/C switch inside lights up when its depressed and the fan is on.
4. Fuses - have checked both the 60 amp and 30 amp fuses in the engine bay. Power going through them and no issue there. I checked pre and post 12v with a test light.
5. Relays - I bought a brand new correct amp relay from the local auto elec in case that was the issue. I placed the new relay in the clutch relay position in the driver's footwell. Didnt fire the compressor up. I also placed it in the other relay position - no change. I note that when the relay is disconnected the dash light on the A/C button doesn't light up. So I assume that the relays are fine as the dash light comes on either with the new relay or the old one.
6. Gas pressure - Fridgie mechanic in Yea tested the gas. Plenty of gas on board.
7. Thermostat with burdon tube. According to the rave manual, this also controls the clutch. It says the following:

1. Compressor
The compressor (1), belt driven from the crankshaft pulley, pressurises and circulates the refrigerant through the system. Mounted on the compressor, an electro-mechanical clutch maintains the correct temperature and pressure by engaging or disengaging to support the system’s requirements. The clutch action is normally controlled by a thermostat located at the evaporator (5).

So the clutch is also controlled by the thermostat located on the evaporator. I pulled it out of it's location (as per my description earlier) and put some contact cleaner through it. At this time the law of garages and lost tools came into play and my test light went missing (because I need it obviously) so I can't test the two terminals on the thermostat to see if power is going into and out of the thermostat on the evaporator.

So my question is - what setting do I have the multimeter on to test that there is power coming into and out of the thermostat switch? I've no idea. I should google that.

As I have tested everything else in the system, the only things it can be (according to my little brain) is either a broken wire somewhere in the system (the thread I quoted earlier showed that's possible as the loom goes over the steering wheel) or a broken thermostat.

I mean the clutch on the aircon could be knackered and only fires up when I jump it, but that seems unlikely. I have it booked into an A/C legend in Shepparton on the 10th of Jan but wanted to see if I could fix it before then. The guy in Shepparton helped me get my aircon working in my old Ford Fiesta for a 10th of the price quoted locally. He was really good and comes highly recommended. Hence why he's booked out until Jan.

So I'm a bit stumped. Will learn how to use my multimeter or find my test light and test the thermostat. That seems the most likely culprit.

Cheers for all the responses team. Appreciate it.

With the multimeter put it on DC Volts range that is higher than 12. Black lead to ground on the chassis and you should se a figure of around 12 when touching the red probe to where there is power.
Attachment 175676

ITS FIXED!!!!!! [bigsmile]

So somehow the two lots of A/C wiring going into the coolant thermostat (on the front of the engine head) was swapped - probably when the previous owner had the head put on. When I redid the head gasket I made sure the wires went on the same way to the Front A/C Evap Temp Switch (X101) and the clutch switch next to it as they enter the thermostat body. Turns out, they had been swapped around at some stage.

The wiring diagram in the rave manual saved me. And now I have working Air-Con. So stoked! I swapped one set of wires on the rear switch with the front switch wiring to line up with the manual and bingo. Air Con works as it should

Thanks for everyone's inputs. It quite often the simple things that work!

Should make a much nicer trip next week in 38 degree heat!

One thing though - does it matter which way around on the individual switches (now I have that correct) that the connectors go? Which colored wire goes to which connector on each switch? Or doesn't it matter? I couldn't tell from the wiring diagrams.

Anyone want to take a photograph of their thermostat elbow so I can see which way around they are supposed to go?

Id assume that the A/C wouldn't work with at all if they weren't on the right way around.

So they are PRC3359 and PRC3505 - how can I test with a multimeter to see which side is which? Because I assume that can be placed in either way around? So what's correct in one may not be in another?

On mine the first sender has the yellow wire to the front of the car on the second sender it looks like a black wire to the front.
Attachment 175678

Quote:

---

Originally Posted by Fattima

On mine the first sender has the yellow wire to the front of the car on the second sender it looks like a black wire to the front.
Attachment 175678

---

Awesome. Thanks mate.

Good to be a bit more certain with an already established working version, but I don't think the orientation would matter.
The clutch cutout switch is a simple switch .. on or off .. one it hits a certain temperature.

I assume the way it works is that once coolant temp has hit xxx degrees, the switch turns off and power to A/C clutch is then off(minimising heating up even more) ..

Think of it as a generic switch, for say, a light .. it just completes the circuit.

The other temp switch(behind) is for the aircon condenser fans to come on when the coolant temp gets too high(overheating).

I'm not 100% sure of the wire orientation of that switch tho. This one is a switch too, but in RAVE the switched positions are marked [1] and [2]
each number relates to a temp range.
[1] less than 94°C, [2] more than 100°C
With this switch, I think it operates on ground only, so that if coolant temp is up to 94°C, front condenser fans are off(if A/C is already off tho). But if coolant temp exceeds 100°C, then earth [2] is then activated so fans come on, even if A/C is off.

Obviously when A/C is switched on, feed to the condenser fans is from the AC electrical system .. ie. no matter the coolant temp, AC fans always come on.

But it's when coolant temp hits 100°C, is when you want those condenser fans to come on to help Dolores to keep her cool too.

Being circular screw in devices, I'd say whether the 'correct pole' is oriented back or front will depend on the amount of tightness applied, thickness of any gasket( I reckon a copper washer) .. etc. So may vary between one vehicle to another.

If you look up in RAVE page 629 clutch cutoff is X259(X denotes a switch number) and C162 (C denotes a connector number). Note that it offers no 'face view' .. ie. I don't think the orientation is important here .. otherwise they would display it's orientation.
Same page, but X113 (coolant sensor for fans) and C146 ... note how C146 offers a face view! .... and that the connector has a specific orientation. ie. it must be important to get the position [1] and [2] conditions right.
I'd assume that if this were the case, and they were wrongly positioned, the condenser fans would be on a low coolant temp, and then switch off at >100°C coolant temps.

Anyhow.. just some assumptions to think about ..

And good to hear you're getting on top of some things with nothing but persistence(ie. it cost very little-nothing).

Quote:

---

Originally Posted by gusthedog

Hi team,

Whilst this thread contains some awesome info its all a bit over my head: Air Conditioner problems
I wanted to create a stand alone thread on this as its the latest drama I'm facing with Dolores the Disco (300tdi). Many of you have probably seen my awful mechanical skill clearly demonstrated in that thread [biggrin]

It's either got to the thermostat, wiring or the compressor itself as I've checked everything else including gas (air con dude), hi low switch, relays (this morning's effort) and fuses - and they are all fine. I will jump the compressor after lunch to see if it works because currently it's not engaging at all. If it turns out that the compressor is fine it has to either be wiring or the thermostat.

Someone in the thread above says that it's easy to change the thermostat with the burdon tube for a thermistor type. But then doesn't say how to do that. So if I find my thermostat is the issue, how hard is it to either replace the current thermostat and burdon tube OR replace it with a thermister type? I note the original author says its an expert level job to dismantle the thermostat and put it back together. I expect to stuff that up completely.

And I NEED aircon or we're going to have to take two cars next week. Which is OK but means I get to drive Dolores sans-aircon in 38 degree heat all week. I'm built for comfort, not for speed so am not looking forward to that.

Cheers and thanks all.

Pricey (aka gusthedog)

---

If everything works but no cold air, you might check the main underbonnet fuse box. Solder is known to crack over time in the module.
cheers