Air vent flow lessens after 15m, blower going strong??

Air vent flow lessens after 15m, blower going strong??

Postby IndoTriton on Thu Nov 19, 2020 5:05 pm

2013 four door 2.8L diesel (no-turbo), 4x4, manual, made in Thailand, sold in Indonesia (no heat in climate controls).

I am having trouble figuring out my air-conditioning and the auto repair people at the small-town Mitsubishi service center and private repair shops are not very helpful. We have confirmed the compressor is engaging, the condenser is clean, and the coolant is charged.

When I first start the vehicle the AC blows strong and cold, the wind on 3 or 4 easily felt from 30-40cm away. After about 15 minutes the air flow out of the vents is greatly reduced, even at 3 and 4 it is barely felt from 10cm away. However, the blower seems to be working just as hard, which I have confirmed with a multimeter clamp on the blower wires, it's pulling about 12 amps on speed 4 whether earlier when the air is strong out of the vents or later when it is hardly felt. Output from dash and floor vents is similarly weak, fresh and recirc.

If the vehicle has not been used, then I start it with only the fan blowing and AC turned off, the strength of the airflow out of the vents remains strong for at least the 30 minutes I tested this.

One mechanic suggested the interior ambient air sensor is often a problem, and I have ordered one to try that, but I have confirmed that neither the compressor nor blower is turning off.

So my question is, is there any physical diversion on obstruction mechanism in the ventilation system which could be causing this based on faulty sensors?

My other suspicion is that perhaps all the air must go through the evaporator and perhaps it is icing up and all but stopping the airflow?

If anyone has experience with a problem like this, or has opened their ventilation system, or has schematics of the ventilation system, your insight would be greatly appreciated.

Thank you.
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Re: Air vent flow lessens after 15m, blower going strong??

Postby DibbyDibbyDJ on Thu Nov 19, 2020 5:35 pm

Do you have a pollen filter? this may be blocked.
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Re: Air vent flow lessens after 15m, blower going strong??

Postby IndoTriton on Thu Nov 19, 2020 11:36 pm

DibbyDibbyDJ wrote:Do you have a pollen filter? this may be blocked.


Do you mean a filter on the intake of the blower fan? There is a spot where a filter looks like it could easily go, and I have seen in my searches that many others put a filter there just above the fan.

But a blocked filter should be blocked just as much with a vehicle that hasn't run in hours as one that has been running for 15+ minutes, no?
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Re: Air vent flow lessens after 15m, blower going strong??

Postby aids84 on Fri Nov 20, 2020 5:54 am

The a/c may not be cycling properly, leading to the evaporator core freezing up and blocking airflow.
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Re: Air vent flow lessens after 15m, blower going strong??

Postby IndoTriton on Fri Nov 20, 2020 2:31 pm

aids84 wrote:The a/c may not be cycling properly, leading to the evaporator core freezing up and blocking airflow.


You mean the compressor running continuously rather than cycling on-off? Do you know, if the compressor is automatically cycling during the off stage does the magnetic clutch to the engine belt stop spinning as well like when it's turned off completely? Mine seems to remain engaged (spinning) continuously when the AC is on, even low.
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Re: Air vent flow lessens after 15m, blower going strong??

Postby aids84 on Sat Nov 21, 2020 5:25 am

IndoTriton wrote:
You mean the compressor running continuously rather than cycling on-off? Do you know, if the compressor is automatically cycling during the off stage does the magnetic clutch to the engine belt stop spinning as well like when it's turned off completely? Mine seems to remain engaged (spinning) continuously when the AC is on, even low.


Yes you should be able to see the a/c clutch disengaging (the plate on the front of the compressor should stop turning)

http://faq.out-club.ru/download/l200_2006/maintenance/Service_Manual_2009_2013/2013/index_M1.htm

Have a look at the circuit diagrams at the bottom of the index, you should be able to find a schematic in there. You could possibly have a problem with the dual pressure switch but you'd need to do some testing.
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Re: Air vent flow lessens after 15m, blower going strong??

Postby IndoTriton on Sat Nov 21, 2020 8:44 pm

Okay, I have made some good progress. I opened the access panel with the AC resistor next to the clutch panel and could see the Evaporator. It was extremely dirty and I was able to clean it well with a hose extension. So I believe my airflow problem is the evaporator iceing up, which is at least partially caused by such a dirty evaporator. There may be a secondary cause also of a sensor/electronic problem causing the compressor to run continuously and over-chilling the evaporator.

NOW... my problem is simply trying to figure out where the evaporator thermistor sensor goes?? The repair man handed it to me and said it's often a problem. I see where the bracket attaches next to the resistor, but the sensor has a cable about 20+cm and I can't find where it is supposed to go.

#6 here: http://faq.out-club.ru/download/l200_20 ... B00ENG.png
Click to view larger picture

also #9 here:
http://faq.out-club.ru/download/l200_20 ... F00ENG.png
Click to view larger picture

The sensor tip looks like this:
Click to view larger picture

It looks like it is supposed to clip into a hole, in the evaporator housing, right? Does it sense the air on the firewall side or the passenger side of the evaporator housing? Any clues on where to place/insert this?

Thank you, searching this forum has been a great help, just stuck on this last point.
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