Semi Automatically Controlled Tempmatic AC - How it works

Hello Everyone.

2007 HiRoof 906 cargo sprinter (Freightliner).

This is a two fold question.

1. Can someone explain to me how the "semi automatically controlled tempmatic ac" system works? (How and does it need to be turned on - what should I be turning my dials to - is there a button i need to push etc.)

2. Our AC does not work very well - if at all. I will feel a slight breeze coming out of the dash - however I can tell if that is just cool air coming from the outside. What is the best way to test the system to know if I need something like a new AC Compressor.

Additionally - I see a button for "AC off RESET" to the bottom left of the center dial.

Please note we do not have the climate control knob on the right side - instead it is juts a clip for papers. I assume this is because we do not have rear climate control.

Thank you in advance.

Usually, if the system is not working, it is loss of refrigerant over time that causes it. My 2007 was very weak as well, and I had it recharged at 100k miles a couple of years back, and it has been fine since.

If the AC off button is not lit up, then it should be always on (on demand)

Set your temperature button down near the low end, turn the fan on medium speed, make sure all dash vents are wide open with good air flow, and see what happens. You should get very cold air out of the vents within a few seconds, less than a minute.

If not, get an AC shop to check the refrigerant. To do it right, AFAIK, they have to extract it, weigh it, and put it back.

Rob S said:

Usually, if the system is not working, it is loss of refrigerant over time that causes it. My 2007 was very weak as well, and I had it recharged at 100k miles a couple of years back, and it has been fine since.

If the AC off button is not lit up, then it should be always on (on demand)

Set your temperature button down near the low end, turn the fan on medium speed, make sure all dash vents are wide open with good air flow, and see what happens. You should get very cold air out of the vents within a few seconds, less than a minute.

If not, get an AC shop to check the refrigerant. To do it right, AFAIK, they have to extract it, weigh it, and put it back.

Click to expand...

This was my assumption.

The AC Fan seems to work fine its just that I'm not getting very cold air..

Is this something that can be DIY with one of those ac/refrigerant top off cans (ive never actually used one) or is it best to just have a shop do it?

The Heaven Van said:

Additionally - I see a button for "AC off RESET" to the bottom left of the center dial.

Click to expand...

That's not "Reset" ... if you squint really hard, you'll see it says REST

...that's for turning on a circulation pump and fan to extract the *residual* heat from the engine coolant *after the engine is turned off*.

It's on page 222 of the 2008 owner's manual

--dick (T1Ns had it, too... but not so confusingly "buttoned")

I guess a feature no longer available on the 2015? I looked in the OM.

autostaretx said:

That's not "Reset" ... if you squint really hard, you'll see it says REST

...that's for turning on a circulation pump and fan to extract the *residual* heat from the engine coolant *after the engine is turned off*.

It's on page 222 of the 2008 owner's manual

--dick (T1Ns had it, too... but not so confusingly "buttoned")

Click to expand...

Ill be sure to check my manual as soon as I get home.

Should I be engaging this button every time i stop the engine? or at specific times and circumstances? I have not been using it.

Thanks Dick - always appreciate the advice and education.

The Heaven Van said:

Ill be sure to check my manual as soon as I get home.

Should I be engaging this button every time i stop the engine? or at specific times and circumstances? I have not been using it.

Thanks Dick - always appreciate the advice and education.

Click to expand...

The only time you would start the REST function is when you want to heat the interior of the van when the engine is not running. It will provide heat for about half an hour.

"Is this something that can be DIY with one of those ac/refrigerant top off cans (ive never actually used one) or is it best to just have a shop do it?"

I'm pretty sure Sprinter AC systems are critically charged -- as mentioned: remove refrigerant, check for leaks, evacuate, weigh in correct charge. If you use one of those cans, you'll never know precisely how much you put in. I don't recommend that route.

The Heaven Van said:

This was my assumption.

The AC Fan seems to work fine its just that I'm not getting very cold air..

Is this something that can be DIY with one of those ac/refrigerant top off cans (ive never actually used one) or is it best to just have a shop do it?

Click to expand...

NO!
You do so at your own wallet flushing peril.
Dennis

The Tempmatic system system utilizes a clutchless A/C compressor that spins whenever the engine is running. The compressor has a variable stroke that is manipulated by a solenoid valve which in turn is contolled by a pulse-width-modulated signal from the dash HVAC module. When cooling isn't required, or when there is some other fault in the system which disables cooling, the compressor is de-stroked to its minimum. If you feel the aluminum A/C lines where they enter the firewall (near the service caps) with the system running, there should be a definite temperature difference, with the larger of the two lines (low side) being colder. If they are the same temperature, the system is likely disabled for some reason, which could be low refrigerant charge pressure, but could also be something else. The easiest way to check to hook up a scan tool capable of communicating with the HVAC module and see what the fault is. If there is some temperature difference between the two A/C lines, then the most likely candidate would be some loss of refrigerant charge, but not enough to disable the system.

A can of Pure 134a (NO OIL OR LEAK STOP) can be used as a trouble shooting tool for those who know what they are doing. This would be done if its confirmed a low charge, and verification of proper compressor operation is desired before spending time/money at shop for a recharge. The best approach is to have a shop evac and recharge the system by weight. That will generally include a leak test.

A good scanner should read the refrigerant pressure. If its below about 45psi in summer temps, its probably lost its charge. If its higher, and climbs with the AC on, then you may have a low charge, or bad compressor/control valve.