w163

Hi
continuing the AC drama - 1998 ml 320
Went to the local MB dealer for o rings etc and was found out that 4oz of their PAG 45 - $275.00!!!

So work done so far - replaced

1. Expansion valve
2. AC compressor
3. AC line condenser to compressor
4. AC dryer
5. 3.5oz of PAG 45 to compressor (shipped dry)
6. Blend motor/ actuator

Added 12oz of RA135 - the system calls for 26oz

AC on - compressor running - face vents - blower motor at 3 - Cold air!!!!
Reading 6.5 bar - scanner
However the AC manifold gauges are wacky - outside ambient temp is 60 degrees (humid) High lowside pressure and low high side pressure

Does anybody know what is going on here?

Thanks

Hi low side pressure - low high side pressure, compressor engaged, ambient temp 60degrees Cool air at in car air vents

iCarsoft scanner live data ac system pressure

Only added 12oz 134A system fully evacuated and on vacuum pump for 1 hr.

w163

AC readings ok
Fitted an aftermarket AC compressor and battled some leaks - mainly at compressor suction fitting, hopefully new o ring has fixed this
The guages are now reading ok, and refrigerant pressure 14.5bar, there is cold air in the cabin.
Now the last issue - check engine light - P1453 stored

1. Air pump relay (K17)
2. Air pump relay (K17) relay module K76, fuse and relay module K40/4
cannot get rid of this annoying issue
Any advice welcome on this one
thanks
PDG

Maj. Dundee

That is the correct code, but your scanner has given you wrong info on the relay #K17 which is for a different model.

The correct relay is K28. Before a cold eng. start, remove the eng. cover, then remove K28 and substitute with K 21.

Then start eng.and feel the AIR Pump to see if it is working. It will run for a while and then shut off.

w163

Maj Dundee

RE : Relay K28

Thank you for your reply.
- Removed cover from relay K28, if I close contacts - no ignition on - air pump will run
- Start car relay does not close - if I close contacts Raif pump will run.

There must be no signal to that relay - what’s next?
Check engine returns after ‘clearing’

Many Thanks

Maj. Dundee

I suggested that you swap relays and you completely ignored it.

w163

Hi
Thank you for your reply
I have in fact swapped out the relay, and this is the relay shown in the test - the thread on this issue will show that swapping this relay was one of the things done in an effort to solve this issue.
The fact that the relay works - ie sends power to the air pump, suggests that the problem is else where.
It must be that the NE/10 ME control unit is not sending a signal that K28 relay.

Surely this is not the only ML that has had this issue!

Thanks

E55Greasemonkey

On a 22 year old ML pull the bulb for the check engine light and move on with your life.

w163

Thank you for your observation.
Not sure if this is the direction I want to take.
Difficult to move on if it is not possible to get a ‘state inspection’
There must be a logical explanation and equally logical fix for this.
As for a 22 year old Ml every thing else is functional and and in good shape
Thanks

E55Greasemonkey

If you have state inspection then it's a different story. Typically the electric air pump goes bad (either seizes or draws too many amps) and burns out the relay, which can in turn burn out the fuse box internally. The fuse box inside is layers of circuit boards.

w163

Dear E55
Thank you for your reply
The relay and all things down stream - on this circuit are functioning ok.
It must be the signal to the BCM - (or the BMC itself) that is causing the issue
Questions -
1. where is the BCM located?
2. Does any one have a ‘pin out’ of the BMC showing what controls the K28 relay / 40 Amp fuse and air pump.

This is the last obstacle to overcome before handing this Benz over to my son. (He is currently driving a 2002 ML) which I will then give to my brother-in-law., my wife and I also drive 2002 / 03 ML’s each also have the high milage award from Benz

There are 2 additional small issues to overcome
1. The rear washer does not spray - the pump works.
2. Replacing the small bulb / illumination for the HVAC control.

I have the high milage award from Benz as this ML has over 250,000 miles and is running strong.
Keep calm and carry on Benzing.

Bezalel

Hi, Did you get your AC working properly in the end? My AC in my 2000 ML320 doesn't work, but I'm leaving it alone as it can get expensive to fix. Where I live there are only about three days a year when it would be useful... Well done on the high mileage awards! Mine has only done 126700 miles and only 16000 of those are mine, in the last nearly seven years, so I should get a low mileage award...

w163

Hi Bezalel
Thank you for your message. Yes after much drama with a leak at the suction side at the compressor, finally got the ac working.
used after market parts including a replacement compressor and did the work myself to keep costs down
The compressor has 3 securing bolts, however in true ml style one is a real sod to get to.

The wacky guages were due to operator error. I had the wrong valves open.
live in Houston so ac is a must!
Still cannot get the check engine/ smog pump issue fixed