Air-cond is not Cold, What Could it Be Now?

I took Rhino out for a drive today to get some lunch. As the car was not warmed up properly yet, I decided to let the car idle while I packed, and 10 mins later, I noticed that the temperature was idling at about 90c.

I checked the engine bay if the fan was running and it wasn't. So I decided to check and look around if there is any clue that could be causing this. I noticed that the cable that connects to the aux fan resistor or aux fan ballast seems to have had its insulation melted. This is strange as the insulation was corrected not too long ago.

I called the wireman to share my observation and he mentioned that the issue could have been a bad resistor or aux fan that was drawing too much current. But till this is checked in person, we will not know for sure.

I called the AC guy after that to get some opinion, what he shared was new learning for the day:

The Aux fan will trigger at a low speed once the AC pressure reaches a certain level
When the freon level is low, the pressure will not be high, hence the aux fan will not be triggered
As this car is fitted with the 95c coolant temperature switch, the high-speed fan will trigger and bring the temperature lower to below 90C (if I am not mistaken)

Other observations that were seen were:

The temperature was hovering below 90C when the car was in motion
There are no issues with the AC when the car is moving
A high-pressure hose was cold with vapor condensing on it - this removed a faulty compressor out of the equation

When I did the wiring work on Rhino, the aux fan resistor was replaced with a used one. That could have been faulty and as remediation, I managed to scout for a new genuine one (made by Beru) that fits Rhino and hope that this will sort the problem, assuming the resistor is faulty.

I am also planning to do a complete AC overhaul where the entire system will be checked and refreshed accordingly. There could also be a leak somewhere on the AC piping that is causing the freon gas to leak. This too will have to be fixed or a mutation of this issue will reappear again in the future.

A video of the melted resistor insulation cable can be viewed here.

Update #1:

I did check the aux fan relays, it is located at the extended fuse box, that needs to be unscrewed to be accessed. There are 2 relays for the aux fans, also called the pre-resistor relays. The first one is for the low speed, the relay is equipped with a 15A fuse on it, the second is a high-speed relay, which is equipped with a 30A relay.

The relay low-speed relay looks like it will need a new fuse, if not a replacement relay. The high-speed relay looks like it has been replaced, back in 2005 and is still functioning since the high-speed fan kicks in when the coolant temperature reaches 90c.

Update #2:

I checked the existing stage 1 aux relay and found that the one on Rhino had a 30A fuse instead of the 15A fuse. Furthermore, the fuse has been burned and further burned into the relay. I did replace the relay with a new one, but there was no improvement to the low-speed fan.

As a bypass, I disconnected the pressure switch at the AC drier and jumped both leads, while there were sparks, the aux fan did not run at low speed as it should.

Update #3:

Rhino has been sent to the AC guy for a complete AC rework/overhaul. The entire work would consist of diagnosing, testing, running in, monitoring would take approximately 10 days. I am not rushing the work and would like it to be done properly. I will also take this opportunity to have the dashboard swapped from the one with SRS to one with a glovebox. There will also be a thermostat hidden that will enable the AC temperature adjustment, presently, it is only blasting on full swing or off. The entire system will need to be checked, the compressor may be on its way out. The cooling coil may need replacing, the AC blower is working, but there is no telling how good it is at the back of the dash, a thick blanket of dust over it is certain.

Update #4:

There were some updates on the AC works today:

The compressor is no longer efficient
There is a leak on the discharge hose (the hose that connects the compressor to the expansion valve)
The outlet on the condenser has been bent

As a result, the recommendation was to have the compressor replaced, a Denso Japan compressor was sourced. The expansion valve and cooling coil will be replaced and we got the replacement that is Hella made. Drier will be replaced as well to one that is made in Korea. As for the leaking hoses, those will be made to measure. To ensure proper reliability, the blower motor will be replaced as well, it will be a lot cheaper to do it now compared to later.

Update #5:

More updates on the AC work:

Dash has been removed, and evidently, some work has been done in the past. The back of the dash was very dusty as expected
The windscreen air duct has been closed but was not sealed properly, it was closed with some duct tape, meaning cold air was sipping out onto the windscreen
The fresh air intake duct has been sealed shut and the cabin filter removed
A thermostat has been added previously, but it was positioned behind the dash and was inaccessible, it takes a champion to install a thermostat like this. the left leg air duct was damaged as well
The compressor was found to be leaking
The compressor discharge hose was leaking but it was also short, due to the engine and compressor movement, hose damages were expedited
The cooling coil was dirty
The passenger-side airbag is still in place
Old aftermarket alarm system found, this will need to be removed eventually

All ordered parts have arrived and the cleaning and installation process will begin. The phase of work would involve:

A less popular route to replace the dashboard with a passenger airbag to one with a glovebox, to me being functional was more important than style, the SRS is not working and I have no intention to make it work and test a 26-year-old airbag that could potentially explode when deployed
Clean up of all AC components
Clean up of all the mess at the back of the dashboard
Customizing of new AC hoses to ensure proper fit
Replacement of the aux fans
Replacement of the aux fan resistor
Restoring the connectivity and function of the aux fan stage 1 which was not working
Replacement of the left and center air vents which are broken and ensure that flap lights are connected
Installation of a temperature thermostat that will be hidden under the dash of the driver side

Let the works begin!

Update #6:

One thing that I do not like doing and do is working in a piecemeal manner, meaning not looking at the overall task properly and finding what are all the issues that need to be resolved. It irritates me when someone works like that as it makes it all challenging for all the different parties involved. So I am always looking to work with people who are able to be independent in the job scope that they are engaged for and deliver as smoothly as possible.

At this moment, I have been updated that all the following items have been installed:

Compressor
Condenser
Drier
Aux fans
Aux fan resistor

One of the plastic pieces of the blower enclosure was broken, the AC guy took a piece of zinc and riveted it to place to patch the hole.

The replacement dash with a glovebox is being installed and we hit a snag. The glovebox liner was not available in the replacement one. We will need to source for one and that was a panic moment, however, the situation was promptly recovered when we were able to source the glovebox liner, glovebox lamp, and also the rivet clips and they are all brand new genuine parts. Items will be delivered to the AC guy for completion of the installation of the dash. Next one the list is to have the AC vents installed.

Subsequent to that, the blower and cooling coil/heater core has not been installed because it has to be mounted over a rubber piece that drains water from the center of the windscreen out. The said rubber piece is not available when the blower box was removed, probably removed when it was worked on in the past. After a lot of finding, the part was found brand new by someone who is located 200 km away. The said part will need to be ordered and it will be shipped to me. And as life would have it, after paying for a brand new part, the ordered part was not the correct one. A few calls later, a junkyard found the needed rubber drainage that is located under the blower. As this is one of those parts which will be installed and will not be seen again for some time, I will have it cleaned up, treated with a rubber softener before passing it to the AC guy for installation.

This AC rebuild is turning to be more complex than what I anticipated, which makes me think, Rhino was probably not managed well in the past and was left to rot until I got it. I did see evidence that it was well-loved in the past with some of the expansive audio parts found in the car, but I am guessing it changed ownership after that. I just hope that the complexity reduces from here on.

Update #7:

More updates received on the AC work:

The blower case has been assembled and is ready for installation
Airflow to the front windscreen has been completely sealed off. At times, when the air vent actuator to the windscreen is not properly shut, it causes the lower front windscreen to vaporize
The fresh air intake flap has been sealed shut. Again over time, the flap does leave a gap and that causes the exterior smell, fumes, and smoke to be sucked into the cabin. This will also remove the need for a fresh air cabin filter that is located under the wiper
Metal hose and valves from the condenser and also into the compressor have been fitted

The update that was shared today was that the discharge (high pressure) metal connector in the past was not fitted with the correct diameter one and instead it was fitted with the low-pressure one. This causes leakage at the joint.

Subsequent to that, the compressor intake hose was short and did not compensate for the movement due to engine flex, which caused some leaks as well. All this will now be corrected.

Lastly, the front cowl where the blower box is installed was not rusty. This is a pleasant surprise. All that needed work was the refitting of the drainage rubber hose. The rubber hose also acts as a blocker for fumes to be sucked in by the blower. It functions almost like a one-way drain. We are not too sure if this will solve the smoke and petrol smell that is coming in the car, but the suspects left are reducing after the AC work.

From this point onwards, the AC guy will work to reinstall all components back, install a hidden thermostat and test the AC system.

Update #8:

Minor update today:

The Center cowl drain has been fitted with the two-prong drainage rubber
The dashboard has been reinstalled, a thermostat is to be fitted soon
Refitting in progress for all other components

Update #9:

All AC parts have been refitted and Rhino is now fitted with a non-SRS dash and a fresh glovebox liner.

The hot water system has been disconnected and removed so the original thermostat no longer works. As a workaround, a thermostat has been planted under the dash on the driver's side to allow temperature control.

The car is being tested to ensure that the AC system is in good shape and extra sound, noise, or even leaks are observed.

I was informed of a new issue today where the car would not crank on P, and will only crank on N. This is caused by a faulty starter blocker switch on the gearbox. I will leave this issue for another day.

Update #10:

The car was ready for pick up and while picking it up, I wasn't impressed. The AC was not as cold as I expected it to be. However, thinking that it was due to the new system that hasn't break-in.

I took the car to a mechanic that I have been frequenting to resolve the faulty starter blocker switch, or else, I will have to only start the car at N until either even that fails or replacing the switch.

I bought the original replacement and had it delivered for installation to the mechanic's garage. I also bought the Mercedes Benz Citric Acid to flush the cooling system.

An hour later, the new starter blocker switch and cooling system has been flushed and added with the citric acid.

So I made my way home and hardly 30 minutes later, disaster struck. The temperature rose up to just below the redline, something is definitely wrong.

I pulled over to allow the engine to cool down. Since my high-speed aux fan is triggered at 90c, I switched off the engine to allow the fan to cool the radiator down. At this temperature, it took almost 15 minutes of rapid cooling before the temperature reaches below 90c.

I checked the engine bay and noticed that the serpentine belt was damaged.

A quick call to another mechanic who happens to be about 5km from my location and updated him with the situation, I cautiously drove there, keeping an eye on the temperature and maintaining it to not exceed 95c.

I updated the AC repair work and also about the flushing. He was not amused when he heard about the citric acid flush and gave me an earful for that. While allowing the engine to cool down, we noticed that there was a small pool of engine oil on the floor.

He jacked up the car to check and was concerned if the engine had cracked, gasket failed, or even more irreversible damage.

Once the engine was cooled down, they first had the belt replaced followed by washing the engine bay to narrow where the engine is leaking from.

Nothing could be seen at the moment, and he went ahead to flush the cooling system with water to remove any citric acid residue. When the rubber hoses were removed, I could see that the metal hose sockets are clean, but this method of cleaning may have been aggressive and must be handled with care.

After the flush, I made my way home and I was impressed that the temperature maintained between 78 - 82c while in motion and stop and at any speed.

Once home, I spent the time learning fiddling with the AC thermostat to understand how this AC works, after a number of spins back and forth, the temperature started adjusting with the thermostat position. So the thermostat was faulty earlier, and it works properly now. However, I would like to check how does the AC work without the thermostat as I am feeling that the resistance is too high that it is not allowing the AC to be cooler.

Strangely, after having the belt replaced, the car feels lighter and possibly due to the refreshed AC system. I seem to see that even the fuel consumption has improved a little, but I will be able to confirm once I complete this round of fuel. On average, I get about 450km to a tank, and if I get to beat this number, the car has definitely improved, albeit losing some power due to a leaking exhaust system.

After allowing the car to run in with the new system, the car runs cool and can get pretty cold. This entry rests here.

Hot tips:

For an old car, it's good to do a proper overhaul of the AC system
For an older car, R134a refrigerant may not have been used, R12 would have been used instead
It's good to update the system to take R134a. However, a conversion needs to take into consideration that particles are finer for R134a compared to R12, and hence the compressor, piping, valves among others that need replacement to avoid leakages
Also, important to know that different refrigerant uses different compressor oil types and they do not mix with one another.

Pictures:

Aux Fan Resistor - This picture was taken from the net

The current aux fans on Rhino are no longer efficient

The relay compartment is behind the fusebox. The Aux fan relays are located at the first row, 2nd (blue - 15A fuse - low speed - burned), and 3rd (green - 30A fuse - high speed) from the top