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2002 CLK320
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Hello,
I have a 2002 CLK320 with 130,000 miles on it. I live in Phoenix AZ where the temperature is hovering around 100 these days. The car is not overheating. The temperature gauge stays around 90. I changed the thermostat about 6 months ago and flushed the coolant.

Please understand that I'm a backyard mechanic so if I state something incorrectly please forgive me. I have scoured the forums looking for information and found many great posts. Unfortunately for me, they seem to contradict each other sometimes so I'm not sure what to do. I've found items related to the fans, DUOVALVE, Aux Circulation Pump, Freon, etc. All seem logical.

PROBLEM: My A/C suddenly started blowing hot air. The error I got on the EC readout was related to the Aux Circulation Pump, error code B1416. I don't want to buy the part until I can confirm that's definitely the problem. Maybe it's been bad for a while? I don't know how to test it.

TESTING SO FAR:

1. FUSES: All fuses look good

2. ELECTRONIC FAN: Fan runs fine

3. AC COMPRESSOR: Clutch seems to be spinning whenever the engine is on. I don't hear it going on and off.

4. SENSORS: I ran two EC tests to get the sensor codes. The first time I pulled the codes the car had been running about an hour. The second time I pulled the codes the car had been running about 20 minutes. (Also, I pulled the codes first thing in the morning after the car sat all night. I couldn't get any codes to show up)

Here are the results from the two tests:

SENSOR 1ST TEST 2ND TEST
1 102 102
2 103 103
3 143 104
4 116 105
5 115 101
6 171 194
7 11 9
8 114 111
9 0 0
10 6.0 6.0
20-23 0 0,
24 12.1 12.1
40 8 8
41 5 5
42 248 248
43 14 14

The EC display showed error code: E 61 416, which I understand translates to B1416 - Auxiliary Circulation Pump.

4. TESTS:

SYSTEM CHARGE: I wanted to make sure the freon wasn't low so I picked up a recharge kit. When I attached the gauge, with the car running and the AC on high and the compressor engaged, I went way into the Red zone. According to the instructions, if the compressor was running then I was not supposed to add any more freon, so I didn't.

AUXILIARY CIRCULATION PUMP: I disconnected the wire harness attached to the pump. I stuck my volt meter probes into the harness and got a reading of 13.5 volts. I then put my probes on to the two pins on the pump to test for continuity. The continuity test failed. The car was running and the AC was on when I did these tests.

QUESTIONS:

1. Can the Auxiliary Circulation Pump cause the unit to just blow hot air?

2. Is there a way to test the pump to verify it's bad? I tried touching it while the car was running but couldn't tell if it was on or not.

I greatly appreciate any thoughts you may have to help me diagnose this problem.
 

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2000 E430
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44 Posts
Haven't heard from grcclk320. Would love to solve this! I will let you know what I find. Seems like this is not a freon pressure issue, but something with the control system turning off cooling because of a detected problem with the circulation pump. I haven't figured out what to try next.
 

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08 ML 320 CDI, 99 ML320 V6, 00 CLK430 Cab
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536 Posts
Well I checked my freon and it was good. The compressor works but no cold air. I'm going to take it to an indy shop and have them look at it. It might be a while though. I'll keep you posted and you do the same.
 

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2000 E430
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44 Posts
I'll be interested to see if an indy shop can solve this. I think it's a Mercedes control system issue, not a standard air conditioning problem. I will keep you posted. Thanks.
 

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2000 E430
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44 Posts
Thank you. That's part of how I ascertained the b1416 code. (See first post in this thread.) I also have a high end diagnostic scanner that can plug into the Mercedes port under the hood at the fuse box. Both methods confirmed the b1416 code. Just don't know what repair actions to take.
 

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2001 CLK320 Cabrio
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358 Posts
From the list of DTCs I have, when using the N22 diagnostic test, that would correspond to the coolant circulation pump (M13) is B1416014.

Here is the suggested MB test step for this DTC

2610893


Don't forget to erase any stored DTCs at the end of the N22 diagnostic scan.​
 

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2000 E430
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44 Posts
Interesting. This appears to be a test of the pump itself. Is it resistance across pins 20 and 28 on connector n22? If so, do you know what/where connector n22 is located?
 

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2001 CLK320 Cabrio
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358 Posts
That's the test for that DTC B1416. It does seem that it's only an electrical test of the M13 pump motor (e.g. the motor winding, bushes and wiring from the pump to the N22 controller).

The connector is on the rear panel of the N22 push button controller, so you'll have to pull it out of the dash, that requires the same 2 thin keys that are used to remove the radio.

You make the measurement on the harness connector (e.g. not the panel connector on the N22), so depending on orientation of the harness, make sure you probe the correct pins.
 

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just a try....did you clear the codes after you did the diagnostics? Clear them (believe it reads FF when you clear it) see if you get the same code reappearing. The MB system will go into safe mode if there are problem codes (no cooling to prevent accidental compressor failure). You say in original post that the compressor does not seem to be running.... In most cases, after MB servicing, the codes must be cleared before AC will become operational again.
 

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2000 E430
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Yes, I've cleared the code a few times, and it always returns upon turning on the a/c. Yes, the compressor appears to be functioning correctly: With the a/c turned off, the compressor pulley is stationary; with the a/c turned on, the pulley is spinning.

Interesting about the 'safe mode.' That explains what I am experiencing with the a/c, even though there is plenty of Freon in the system.
 

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2001 CLK320 Cabrio
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358 Posts
Given that the resistance test for your M3 circulation pump checked out OK, at this time, it's not likely the culprit.

That was the sole test MB showed for DTC B1416, which surprised me as there is usually a voltage and resistance test for DTCs (e.g. the pump motor requires power to operate which presumably is supplied from the N22 HVAC controller). Additionally, as shown in the below diagram, the proper operation of the controller also requires various sensor inputs.

View attachment 2610970

In your initial post you mentioned that all of the fuses looked OK. For completeness, those would have been the fuses in position 20, 25, 26 and 38, located in the engine bay, driver side F1 fuse box. In addition to viewing the element through the sight glass, put a voltmeter on the top metal tab (e.g. to check that the fuse has 12 volts present in the input and output) and also pull each fuse and inspect the contact for corrosion (e.g. because the voltmeter test only requires negligible current draw to pass, while contact corrosion adds resistance that will inhibit a high load current to flow ).

Try operating your HVAC only in manual mode. I have a cabriolet, where I operate my HVAC system in manual mode only, which extends the top down driving season, by manually providing cockpit heat or AC (e.g. irregardless of outside temperature). It's like chicken soup, it may not do you any good, but will do you no harm.

BTW, does your N22 controller EC button lamp always remain lit ?
 

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2000 E430
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44 Posts
Thanks, will thoroughly check those particular fuses. No, my EC button lamp does not stay on in this car. My other w210 did have that issue in conjunction with no cold air from the a/c.
 
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