Auxiliary Fan Emergency!!! Picture of blown fuse - Mercedes-Benz Forum
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post #1 of 16 (permalink) Old 07-14-2016, 02:14 AM Thread Starter
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Auxiliary Fan Emergency!!! Picture of blown fuse

Ac was working perfect today. A few hours into driving off and on i noticed the air was getting hot, so i lifted the hood up and noticed the ac compressor wasn't running, and i checked the low port pressure and it read 200 psi. I was stupid and released some refrigerant, & in front of a cop, also i noticed the coolant tank was bubbling. Without an instrument cluster i had no way to tell the temp. After i got home i let the truck cool off; i checked the fuses and noticed the ac fan fuse was blown . I replaced it; turned the car on the compressor is back on, but the fan is still not running. My question is does the fan come on when the AC is on, or only when the engine warms up? I was told the AC will work for a while without the fan, until the pressure builds up to high then the compressor shuts of for safety of course, that's why my AC was working even after the fans failed. Now i may need to hook the fan directly to the battery to see if the fan is still good, also called the DC test. Then i may need to check the Coolant temp sensor, but i am still looking at every wire and sensor.
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post #2 of 16 (permalink) Old 07-14-2016, 02:46 AM Thread Starter
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Update

I hooked up my OBD 2 and only found a P0130 usually a oxygen sensor fail, but i am repacing the cats in September anyways. Right now i am going to start the truck and let it warm up to see if the fans kick on and to test the AC.
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post #3 of 16 (permalink) Old 07-14-2016, 04:05 AM
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The fans will only come on once certain parameters are reach with engine coolant temperature and A/C pressure.


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post #4 of 16 (permalink) Old 07-14-2016, 05:02 AM
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Originally Posted by mattml430 View Post
The fans will only come on once certain parameters are reach with engine coolant temperature and A/C pressure.


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Exactly and here they are. If the fuse keeps blowing, you will have to have the circuit rewired.
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post #5 of 16 (permalink) Old 07-14-2016, 08:40 PM Thread Starter
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First thanks to all for your help. Update: I unplugged the coolant temp sensor and my fans turned back on. I will be removing the senor to see if the new one will turn the compressor back on for the AC. I read that if the coolant sensor fails it will turn off your AC compressor is that correct?
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post #6 of 16 (permalink) Old 07-14-2016, 10:53 PM
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Turning off/locked compressor is only possible with 2002 MLs and above.

The overheating was caused by the blown fuse which operates the Cooling Fans.

What you should do is, working with a cold eng., reattach the connector to Refrig. Pressure Sensor and make sure the coolant level is correct.

With the A/C off, start the eng. and monitor the temp. gauge. If the gauge rises quickly then the fan clutch is faulty.

If the temp. rises slowly to 80C, continue to monitor the gauge. If the temp. rises past 100C and the fans do not kick in, then your Coolant Temp. Sensor is at fault.

All during this time you must monitor the two elec. fans, the clutch fan, the overflow tank and the temp. gauge. It would be best if one person monitors the gauge and you monitor the rest.

If everything works fine with the A/C off, then it is strictly an A/C issue, probably low on refrigerant.
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post #7 of 16 (permalink) Old 07-15-2016, 04:41 PM Thread Starter
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Thanks i will do what you said, but i dropped my securing clip for the Temp sensor now i can't do anything until i get a new one or find the old one. The clip is so hard to get back in! I had a huge puddle of coolant from taking out the sensor.
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post #8 of 16 (permalink) Old 07-16-2016, 11:55 PM Thread Starter
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Update: my fans turned back on at around 90- 100 celsius. I changed my coolant sensor, then i disconnected my battery. The compressor is back on, but no cool air. Low port psi is about 20 psi which is low, bought some EZ chill at wallmart wasted one bottle already from a bad connection, i got a new one, and will add it tonight. I drove the car for 6 hours and no issues at all; temp was about 85 celsius all day. Bonus my instrument cluster is back on!
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post #9 of 16 (permalink) Old 07-17-2016, 02:03 AM
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You are low on refrigerant.
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post #10 of 16 (permalink) Old 07-17-2016, 09:54 AM
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Yes you are low on refrigerant most probably from that "atmospheric release" in front of John Law. Lol. Good luck.
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