Have air flow issues with this truck since we bought it. Could feel the A/c cool but no fan. It was fairly warm in February when drove out of Melbourne during the bushfires.
On a sideline to this topic, driving a decommissioned ambulance through Melbourne traffic during the fires, with your lights on, is a quite easy way to move through traffic, even the boys in blue waved us through an incident
Back to the topic in hand, the fan motor didn't work. Upon investigation, and removal, the brushes had worn beyond their serviceable limit, "gone" as they say in the cricket The local autoleccy came through with some "will fit" brushes and after some time refashioning the shape on a linisher belt, fitted them in and "we were away".
Alas still not a great deal of air flow & or cooling. This A/c has a secondary unit for the ambo body, one compressor with a T piece for gas to the cab and to the rear.
With the total system on, the rear is great, plenty of air along with cool temperature but the front is barely cool Upon further investigation, the front only switched on, the pipes to the evaporator freeze up, stopping airflow to the cab.
So, with some research through the "heating, cooling A/c" section of FTE, a common issue seemed to crop up again & again, dirty evaporator.
The remedy- strip away the cowling and clean with a broad selection of solvents ranging from truckwash, air, truckwash and flush with the garden hose, pressure pack carby cleaner and the good ol' pressure washer in combination, a couple of times. Now you can see through the evaporator, so hopefully, this will solve the air flow problems
Sorry can't post any photographic evidence as I don't have enough access yet

 

Completed the final re-assembly this morning Fan feels like it has two more speed settings! So it was the blocked up evaporator causing the reduced airflow.
Temperature is 33c (90F) today, well its spring in the southern hemisphere so having the A/c functioning at its potential will be nice.

 

That's a result!

No a/c re-gas necessary?

 

There's always room for a top up

 

After a run today with the air con working, something was still not right! Evaporator pipes were icing in the engine bay but not artic temperatures flowing inside the cab
Pulled the glove box out to expose the next box behind it. Thought, this plastic box is fairly warm. &!##dy heater element, hot as Hades (hell). Soon fix that little side issue. Forget tracking down leaking vacuum hoses etc, disconnect the offending hoses and block off the outlets. Don't need a heater out here. If your cold, windows up and a coat for 20 minutes and you're toasty

 

Hey Russ, check out the MAX-A/C assist mod. Sounds like the stock set up you have still has the coolant running through the heater core when the a/c is on. You add a vac operated valve and T-piece so that the coolant flow to the heater core is turned off when the HVAC control is on max-AC.

 

Another deserved thank you I thought there'd be a "correct" solution but did the bush repair anyway. Put a bypass hose on the engine with some spare heater hose left over from previous car projects.
While I was under the bonnet (hood) I noticed the thermo fan wasn't switching on. Found the original style relay was (broken) "had the sword", so now, at last, the whole show is working, although, I need to fit a noise suppressor to thermo fan wiring, as my wife let me know in no uncertain terms "that truck was interrupting her television viewing" in the house

 

Is this the telly in the truck, or the telly at home?

Max A/C assist - this will give you the idea, coz I'm time poor I just purchased this, but you could source the parts locally:

http://www.dieselsite.com/maxacassis...4-200373l.aspx

 

The parts look like the same valve I had on my XB hardtop. Vacuum operated tap for the heater. Should have a look in the shed probably still got it on the shelf It was easier to just disconnect the hoses as I never use a heater

 

After replacing the foam piece between the blower & vents in the depths of the dash area to stop the air from just recirculating around under there, I thought I'd test all the A/c units, turned the front and rear unit (the mark IV style unit in the ambo rear) on to full. No cool anywhere ? So then went to my favorite local workshop man and he hooked up the gas n' gauges. Both units on full, the front unit became icy cold but nothing in the back, great turned that section off completely, don't need it.
So now, after the first 105k (63 mile) towing trip, with the a/c on, nice & cold both ways till near home, the last 15 k's (9 miles) the fan slowed giving less air flow. When I pulled up in town to open up the yard, I turned off the compressor. Upon returning I noticed a large pool of water under the drain from the cab, you beauty, it froze up So now only 1/2 -2/3 on the thermostat has the cab cool in 38c (100F) summer weather (no white Christmas for us down under) but good beer drinking weather.