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Mobile Aircon, Air Conditioner for a Mercedes Benz 4x4 1017A
Saturday, 14 June 2008
After experiencing the scorching heat of Oman in March & April 2008 we felt that aircon (air-conditioner) in this region is definitely no luxury. As we heard from so many others – staying in the UAE or Oman without air-conditioner during summer time is close to unbearable and specially when living in a truck. And we only felt the heat in the springtime with so far relatively low humidity. So staying on the Arabian Peninsula during summer makes Air Conditioning a must have. Just like a heater is during winter time in Europe. But air conditioner installation isn’t an easy job in our case – the OM352 6 cylinder engine is not prepared for such modifications. But if there’s a region with a lot of air conditioner experience, it must be the Arabian Peninsula. So we searched and found an A/C fitter in Dubai for heavy trucks and special equipment – and for those who are thinking about air-conditioner installation too – read on – it’s a long story with quite a few technical details.

AC Compressor installation

An air-conditioner installation in trucks pretty much comes down to one thing – fitting the A/C compressor. The rest is basically connecting pipes and wires from the compressor to the condenser and evaporator. Even when there’s no space in the dashboard, there are units easily mounted on the ceiling or through a roof hatch.

Sanden Mobile Aircon Compressor
Sanden mobile aircon Compressor
Installing an aircon compressor for a Mercedes Benz 4x4 1017A has one major difficulty. Where to install the compressor? There is little space left or right from the engine unless it’s fitted underneath the engine sticking out like a sore thumb between the chassis and front axle stabilizer rod. For a 4x4 that’s a bad position, the compressor gets to chew all the road debris and can be easy knocked out by a stone or branches getting tangled up by the belt. The only sensible position is either at the left or right side of the engine.

Double AC evaporator outlet

Thinking a bit further it would be quite “cool’ if the A/C system not only cools down the front cabin but also the living unit while driving. During the past 2 years we found ourselves inside several times to get away from big crowds building up around our truck. So a little coolness inside would be very welcome. Also compressor installation must be simple without any modifications to other parts of the engine. This to prevent problems with other engine parts as much as possible after the install. And last but not least the connecting belt must be easy to remove from the pulley when the hot season is over. This to save the clutch bearing of the compressor.

In Muscat we spotted a similar 1017A truck with mobile aircon at the Mercedes Benz dealer. Strangely the whole aircon installation was complete, except for the compressor. Looking closer, the designated spot for the compressor was just underneath the alternator. They moved the alternator up creating a little more space. But it wasn’t finished – only the connecting A/C pipes were there. Anyhow this location seemed ok although it’s a very tight fit.

Kysor mobile Aircon Roof Condensor
Kysor mobile Aircon Roof Condensor

Dubai truckers center - Ras Al Khor

Back in Dubai we found an A/C fitter in Ras al Khor – the truckers area in Dubai - located next to the nature reserve Ras Al Khor. The company - Ampex Engineering - is run by a large Indian crew doing all sorts of A/C installations for MAN, Mercedes, Renault, Iveco, Hino and TATA trucks.  The place is always busy and jam-packed with all sorts of vehicles. Looking at the work being done it seemed pretty standard with relatively recent equipment and materials. Ampex is a dealer of Sanden compressors and Kysor A/C units. Sanden is a robust brand that seems to be pretty well known, because their compressors are illegally copied in other countries as we heard from the dealer.

Mobile Air Conditioning outfitter in Dubai - Ras Al Khor

After going through our wishes with the chief engineer, the compressor install seemed a bit difficult but not impossible. Usually Ampex manages to do mobile aircon installations a 3 to 4 working days minimum for trucks. However that all depends on how well a truck is prepared for A/C installation. Our Mercedes Benz 1017A wasn’t for sure. So we estimated it would take at least a full week – if not more. Ampex custom builds the compressor brackets and out-sources pulley modifications if necessary. In our case we needed the pulley modification also. The existing 2 pulleys were already taken by the alternator, water pump and power steering.

Pulley for mobile aircon compressor
Pulley for mobile aircon compressor
After negotiating the price and options we decided to order our mobile aircon at Ampex in Ras al Khor. The additional cost for A/C in the living unit was relatively small compared to the front cabin install.  An A/C standby unit of 220 Volt was way too expensive, almost doubling the price. This makes it possible to use the A/C without the engine on. A more cost effective solution is to buy a small 220 Volt A/C unit from a retailer and install this ourselves. More about this later.

Mobile Air Conditioner installation

following week installation started – in 3 stages – front cabin, living unit and compressor install. In the meanwhile we stayed with friends and drove to Ampex every day for installation supervision which is essential as it turned our later.

While front and living unit installations progressed there was time to take a careful look at the compressor installation.  With 2 mechanics all possible options were taken into consideration. In the end only one remained which was the one we saw on the 1017A in Muscat. The other options required the power steering system to be modified. A big risk because this company installs AC’s and is not a specialist in power steering units.

Following this decision the pulley system was removed and taken to a machine shop to add another pulley for the A/C. In 2 days the new pulley came back – a neat job with a snug fit on the other 2 pulleys. The cooling fan moved a centimeter closer to the radiator leaving enough space to turn.

Mobile Aircon compressor under the Alternator
Mobile Aircon compressor under the Alternator

Essential Air Conditioner Installation supervision

Installation of the pulley system is a procedure with a few tricky stages. A small notch on the crankshaft positions the pulleys, the fan and the vibration stabilizer.  Ruining the notch can result in massive engine vibrations because the vibration stabilizer isn’t set properly. This thick metal disk is positioned a little bit off centre and requires to be installed at the correct crankshaft position. During the pulley installation a mechanic didn’t do it properly and nearly ruined the notch on the crankshaft. Supervision proofed to be essential!

Next was compressor installation starting with removing the alternator. The easiest way is to fit the compressor on the alternator hinge. When swapping the 2 alternator belts with a smaller diameter the alternator moves – creating enough space underneath for the compressor. With this setup tensioning the alternator belts moves the A/C compressor too. To tension the A/C compressor belt, a separate belt tensioner is required. Given the compressor belt has enough slack for the alternator belts to be tensioned first. Equally important is enough space underneath the compressor to move for belt tensioning. So far it seemed all conditions could be met.

Kysor mobile Aircon Evaporator Unit
Kysor mobile aircon Evaporator Unit
The A/C compressor brackets were prototyped with a cardboard sample first. After several attempts one prototype bracket was cut from thick sheet metal. A test compressor was used to check the space around the compressor on all sides. So far it moved freely. With this the second bracket was cut from steel and fitted ok on the first attempt. The alignment of the compressor pulley with the engine pulley was ok too. After this a 3rd bracket locked the compressor and alternator together so they move round the hinge as one pair.

Next was installing the alternator and the new compressor. The pair moved freely round the hinge. Tensioning the alternator belts worked ok so far. The last problem to be solved was tensioning the A/C belt. Important is to put the tensioner in the slack side of the belt so engine power is transferred in a straight line to the compressor. The ideal spot seemed to be on the 3rd bracket itself. The only feasible spot – there was no space left anywhere. After trying many standard tensioner wheels the ideal one was fitted. Although it sat very close to the alternator belt (5 mm space) it tensioned the A/C belt pretty easily.

Kysor mobile aircon Evaporator in the front cabin
Kysor mobile aircon Evaporator in the front cabin
In the meanwhile the 2 evaporators in the front cabin and living unit were fitted. What’s left was connecting the compressor and install the brains of the A/C system which is a set of 6 relays – 3 for each evaporator. The first relay controls the compressor clutch, the second controls the fan of the condenser, and the 3rd drives a solenoid opening either the cooling loop to the front cabin or living unit. For safety a circuit breaker disconnects the power supply when a pressure sensor detects low pressure – indicating a leak. This prevents compressor damage from running dry.

Testing Air Conditioner operation 

After the electricals, all A/C pipes got connected and the system was ready for refrigerant filling. This involves several steps. First the system is vacuumed and tested if it’s airtight. The test failed – there was a tiny leak somewhere. Next oil is injected and refrigerant pushed in. The first stage is to measure how much refrigerant the whole system needs. It turned out to be 1100 grams – which is quite a lot. With a refrigerant gas detector the whole system was checked for the leak discovered earlier. It turned out to be a leaking solenoid valve for the living unit.  Next the refrigerant is removed and used for a second filling procedure. Now the engine was started to check the cooling performance.

A/C Expansion valve
A/C Expansion valve
On the first run their was no cooling at all. The 2 expansion valves iced up on the outside indicating either being blocked by dirt or wrong adjustment of the inside nozzle. After removing the refrigerant again it turned out to be a wrong nozzle setting. All hoses got flushed with cleaner taking another full day to go through it.

In the second run the A/C system started working. As a final check a looking glass on the A/C filter next to the condenser shows if there’s air in the lines. After 2 full filling cycles only a few air bubbles appeared at the looking glass. The A/C was finished and working.

Mobile Air Conditioner spare parts

Mobile Aircon filter with looking glas
Mobile aircon filter with looking glas
With everything installed we went through the whole system identifying essential spare parts before leaving Ampex. Basically the top 5 of A/C breakdowns at Ampex:

-    Leaks at the clamped tube sleeves or seals
-    Broken / slipping A/C belt
-    Dirty A/C filter
-    Electrical problems (wires, relays, fan)
-    Compressor worn out (clutch / piston wear)

We made sure we had the belts, a spare A/C filter and enough seals for all connecting rods. The rest is available in many other countries.

Air Conditioner installation review

Mobile aircon spare part set
Mobile aircon spare part set
Looking back we couldn’t have imagined the complexity of the job. In all the installation took 2 weeks to get done properly. We got lucky we could stay with friends otherwise the hotel bill would be even higher than A/C installation itself. Dubai is definitely not a cheap place to stay anyway. Constant supervision is essential – which means many early hour drives and long stays in the workshop working with the mechanics. Afterwards you can basically start an A/C business yourself. To get to Rass al Khor it’s either by taxi or by rental car. For € 380 a month we rented a Mitsubishi Lancer at Europcar – a pretty reasonable deal compared to doing the same in Europe. We can recommend Ampex but do check out others like Aircomax who service red dot A/C equipment.

Air Conditioner standby operation on mains

WOLF Power 9000 BTU portable aircon
WOLF Power 9000 BTU portable Aircon
With this done we looked around for a small air conditioner unit for operation on 220 volt mains or our 2000 Watt Kipor generator. Amazingly there are a few manufacturers of 1000 Watt compressor A/C’s – because we figured the market must be pretty small. We found a WOLF 9000 BTU (0,75 T) – 1100 Watt portable air-conditioner unit weighing about 35 Kg for about € 180,- at Geant in Dubai. A small unit with remote control, timer, air-filter and a water vaporizing system to reduce energy consumption. The Chinese build Kipor generator can run the WOLF 9000 AC with ease. The AC takes 1100 watt at peak consumption and startup current does not trip the KIPOR generator.

Installation is reasonable simple – the unit needs a ventilation duct to expel the heat from the compressor and condenser. Biggest issue is how to get it installed to withstand the shocks and bumps while on the road. We managed to clamp it down with rubber shock absorbers all round the unit allowing some movement.
With 45 degree heat outside the 9000 BTU unit manages to cool down the insides to 36 degrees. That’s pretty bearable instead of 48 degrees without any cooling.

Read automotive air conditioning for more about the backgrounds of A/C systems.
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