Hi Everyone, I'm chasing a diagram showing the location of all the air con components in my motorhome. I have an electrical issue somewhere in the system and need to find where all the components are located eg. pressure switches, relays, thermostat etc. If anyone has one they could send me that would be much appreciated.. Thanks in advance...

There are normally 2 pressure switches on an aircon system - high and low.

Most likely is is low pressure - gas has leaked out, despite you saying the system has gas. Maybe it is not enough gas? It may work for a while and then stop because the gas has gone into the condenser, condensed into a liquid and has therefore reduced in volume - the pressure then goes down. If you are lowish on gas, this could cause the low pressure switch to come on and stop the compressor until the gas disperses throughout the system again. The system will then start up OK - for a while.

The high pressure switch comes into play when (obviously) the pressure in the system gets too high. This can come about because of lack of airflow over the condenser. Is your electric fan working? If you don't have an electric fan (Tojo Landbruisers don't), maybe the fan clutch is stuffed and not drawing enough air through.

An aircon system has a pump (compressor), evaporator (behind the dashboard) condenser (in front of the radiator) and a drier (normally mounted near the condenser. You should find the switches on the metal pipe going from the condensor to the firewall. They will have electrical wires going to them. If you find them, disconnect them and check the reisistance. If they are low resistance, they have continuity and are operating OK. You can also check the compressor clutch by unplugging the switches and shorting out the contacts in the plugs. If the compressor goes then, check the switches themselves and see if one of them is open circuit (high resistance). That should give you some idea as to where the problem lies.

Jamie and Kerryn wrote:

---

I had the system quickly checked at an aircon specialist and they checked the gas pressure and said the system is fully charged, they also bypassed the two pressure switches by bridging them but still didn't work and then told me to check relays, thermostat etc myself once I found them which is why I was chasing a diagram with the location of the components.. Being a bus everything is mounted half way along the side of the bus and also in the roof panel in the rear of the bus. The assembly diagram for the aircon system would make it a lot easier..

---

 Hi,

You are correct the system is not as straight foward as a car. It has quite a bit more complexity. Look on Ebay for a workshop manual on a CD for that series of Coaster. They are cheap and have most of the information you need and will be posted to you in a few days.

I am not in the country currently but will be home later in the week and possibly may be able to find some info for you if there is no other solution.

Jaahn

Thanks Jaahn any help would be much appreciated..

Hi Jamie,

Could you give some details of your bus so people know what it is. Year, type, model, vin etc. These are all on the manufacturers plate.

Have you searched on ebay for a CD manual for it ?? That's where the answer will be !! Also any other information you will need for other work too, when the mechanic says I do not know what it has. Usually only $10 or so.

Jaahn 

Jamie and Kerryn wrote:

---

Thanks Jaahn any help would be much appreciated..

---

 Hi Jamie,

This might fall under "any help" but no one else has put anything up I did not see any wiring diagrams. You must get the information off your ID plate to find anything.

Here is a site to look up which has the relays etc (and every thing else) as parts and some indication of the locations in the diagrams.Takes a bit of work to get through it. Lots of pages.

  http://toyotapartscatalog.com/toyota/coaster-rb2-bb2-3-hb3-hzb3-hdb20-3-1982-1993-jp/

Here is a CD manual on ebay. Probably the same as factory information. Easier if it's on your own computer.  
http://www.ebay.com.au/itm/TOYOTA-COASTER-BUS-1982-1989-FULL-FACTORY-WORKSHOP-SERVICE-REPAIR-MANUAL-/301369249823?hash=item462b01d01f:g:BWYAAOxyRNJSclOU

Good luck jaahn

Jamie and Kerryn wrote:

---

The problem I have is that the compressor clutch is not engaging when I switch on the aircon, I ran power to the compressor and it engaged and started working and getting cold but then the clutch stopped working and now doesn't engage at all, could be buggered but the diagram would make it much easier to diagnose the original problem of it not getting power to start with. The system has been pressure tested and has gas so there is another problem somewhere else..

---

 Hi Jamie,

How are you going with your Coaster A/C. Fixed we hope

However just some words if not ! My Mercedes Sprinter A/C stopped working a while back and I just put it in for service. The answer was the clutch coil had shorted and bought the system down. But parts were not available, the brand was rare, so the whole compressor had to be replaced for a couple of Gs. The rest tested OK. Not a happy camper !

So I Googled and emailed and the correct part is now on order here locally from a regular supplier and hopefully will be fitted in a few days. ~$100 for part and hundred+ or so to fit we hope. Now that is worth some bl**dy hours on the computer is it not ??

Jaahn