Coolant fan not working C32 AMG

Daveedge

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Sep 14, 2021
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16
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NOTTINGHAM
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C32 AMG
Hi guys

I've recently acquired a C32, decided that I wanted to give it a major service as well as changing out the common issues like radiator and IC pump.

Burped the system, including partially blocking the intercooler water hose and the fan wont kick in neither will the A/C blow cold air.

I get the coolant visit workshop shop message.

So far I've changed out the fan motor and module, temp sensor, fuse 51 in front SAM, fuse 5 in pre fuse box (125a), both of these were fine but I changed them just in case and I've also visually checked for damaged wires and they all look sound. 12v is getting power.

I'm thinking it's the ignition wire but from what I can see of it, it looks sound.

Any ideas?

Cheers
Dave
 
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Daveedge

New Member
Joined
Sep 14, 2021
Messages
16
Location
NOTTINGHAM
Car
C32 AMG
Hi guys

I've recently acquired a C32, decided that I wanted to give it a major service as well as changing out the common issues like radiator and IC pump.

Burped the system, including partially blocking the intercooler water hose and the fan wont kick in neither will the A/C blow cold air.

I get the coolant visit workshop shop message.

So far I've changed out the fan motor and module, temp sensor, fuse 51 in front SAM, fuse 5 in pre fuse box (125a), both of these were fine but I changed them just in case and I've also visually checked for damaged wires and they all look sound. 12v is getting power.

I'm thinking it's the ignition wire but from what I can see of it, it looks sound.

Any ideas?

Cheers
Dave
Just to update the thread-

I've had it put on diagnostics and fan engages at different speeds, so fan, module, wires, fuses must be sound.

There are faults within the AC system due to low pressure... I'm thinking ac pressure switch might be the cause, but I thought if there was an issue with that then the fan ran all the time rather than not at all?

Got one ordered, if its not that then I'm stumped..
 
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Daveedge

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NOTTINGHAM
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C32 AMG
Nobody has any suggestions?

Fwiw if you're ordering a pressure switch there are 2 variants... ask me how I know... the right one should be here tomorrow.

I'm assuming they'll be the same as 320's but c32's use the one that has a plastic end that after the thread. Some switches don't have this, just the threaded insert, not sure which models but definitely some w203's(unless gsf got that wrong as well). The plugs are slightly different and don't mate and the thread is m12 vs m10.

From always owning Japanese cars I stand by Denso products, as good as any other oem manufacturer in my opinion, I got the radiator made by them to hopefully eradicate the coolant/atf cross contamination and also order the dps17006 ac pressure sensor.
 

BPD07

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SLK-32, CLK320 (a208)
Nobody has any suggestions?

Fwiw if you're ordering a pressure switch there are 2 variants... ask me how I know... the right one should be here tomorrow.

I'm assuming they'll be the same as 320's but c32's use the one that has a plastic end that after the thread. Some switches don't have this, just the threaded insert, not sure which models but definitely some w203's(unless gsf got that wrong as well). The plugs are slightly different and don't mate and the thread is m12 vs m10.

From always owning Japanese cars I stand by Denso products, as good as any other oem manufacturer in my opinion, I got the radiator made by them to hopefully eradicate the coolant/atf cross contamination and also order the dps17006 ac pressure sensor.
Sounds like you’re well on your way to resolving the issue. I’ve the SLK32 so know it’s a great engine.
 

Jobsworth

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Horsham
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One or two...
Very likely the fan problem is in the engine ecu. Not common, but seen one or two. BBA used to repair them, but would often fail again a year or two later. They may have improved their repair by now
 
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Daveedge

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C32 AMG
I did think that but was hoping it wasn't.

But after having it on diagnostics and it running the fan at different speeds wouldn't that rule out the ecu/wiring as the program is communicating with the fan through them or not?
 

Jobsworth

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One or two...
Now, I could be wrong on this, but from memory the fan unit is stand-alone, and can be called to duty via the canbus. The air conditioning can send a fan request via the canbus, as can the engine ecu, again via the canbus. I stress, this is from memory, which ain’t so good these days. Star test of fan operation only tests the fan module and the various speeds. I don’t think the test originates from the engine ecu, more from giving it a signal from the front SAM. I’d need to have a pick through Star to confirm it. Maybe tomorrow if I get a moment.
 
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Daveedge

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C32 AMG
Couldn't remove the aircon pressure switch, it's seriously seized on and the required force with a breaker bar would 100% damage the condenser, which is looking worse for wear.

Does anybody know if the switch definitely effects the fan kicking in for engine cooling or if it just effects it working when aircon is engaged?

If its the former I'm going to leave it as it is, if not I'll replace the condenser and switch at the same time.

Think I really need to get it on star now, otherwise I'm just blindly changing parts and wasting time an money, had enough of it tbh.

Does anybody know a good indy in the east Midlands?

Cheers
 

Bobby Dazzler

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Couldn't remove the aircon pressure switch, it's seriously seized on and the required force with a breaker bar would 100% damage the condenser, which is looking worse for wear.

Does anybody know if the switch definitely effects the fan kicking in for engine cooling or if it just effects it working when aircon is engaged?

If its the former I'm going to leave it as it is, if not I'll replace the condenser and switch at the same time.

Think I really need to get it on star now, otherwise I'm just blindly changing parts and wasting time an money, had enough of it tbh.

Does anybody know a good indy in the east Midlands?

Cheers
How far East are you? If you can get it to Mercland in Nuneaton then you won’t go far wrong.
 
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Daveedge

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I'm in Nottingham mate.

Don't really want to drive it too far with the lack of cooling, at this rate I'll be well into winter so it may be an option though!
 
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Daveedge

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NOTTINGHAM
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C32 AMG
Managed to get it off, pressure switch hasn't made a difference and I also got a new relay p just to completely clear the board of sensors, fuses/relays.

I also read about the TSB on the wiring harness adapter so I've fitted one just to future proof me.

Looks like it's ECU or a damaged wire, surely it can't be anything else.

Going to take off the wiper shroud and have a look at the ignition wire, all 4 wires look sound underneath and around the passenger wing so if there's a damaged one it must be around battery tray or bulkhead.

If it all looks good then it leaves the ECU, there's a place in Mansfield that repairs them, will take it in for a test and go from there.

If its not that I may set it on fire... I'd bet with my luck at the minute the fan would kick in then...
 

andy27168

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Are you sure the fan is for engine cooling? As the one on my 202 C43 only ran for the A/C System (Variable speed too).
If it ran for engine cooling it was a last resort to keep the engine cool, it was about 100 degrees IIRC.
 
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Daveedge

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C32 AMG
Hmmmm, well I assume it is because its the only fan, there is no ac/auxiliary.

Being a performance car it should definitely have a dedicated fan that kicks in before 100 degrees or am I missing something?
 

colinallcars

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Hmmmm, well I assume it is because its the only fan, there is no ac/auxiliary.

Being a performance car it should definitely have a dedicated fan that kicks in before 100 degrees or am I missing something?
Does the car actually overheat? I don’t see any mention of that above.
 
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Daveedge

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C32 AMG
Sorry I thought I'd mentioned it, It would if I had allowed it to.

The last time I actually drove it temps were around 100 degrees judging from the coolant warning message gauge (why amgs don't have a standard temp gauge I do not know) and iats were clearly high enough to not engage supercharger the only reason they didn't continue to rise was because I had heater on full blast and I keep on pulling over/turning engine off in traffic.

I haven't drove it since.
 
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Daveedge

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Sep 14, 2021
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NOTTINGHAM
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C32 AMG
Also I didn't realise a normal obd2 reader would work on a merc, I thought it would be star only.

Connects to the ECU fine but can't find any current or stored codes... I thought a code would have been stored tbh.
 
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Daveedge

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C32 AMG
Bought a creator c502 scanner, very good little unit. Made specifically for MB's and goes through the whole system to find faults, quite impressed with it for the price point.

Found faults that all point towards my esp system, but not sure if some of them are due to the battery being disconnected for a prolonged period of time.

If there was an issue with the ECU regarding my fan wouldn't it throw up a fault code, seen those with fan/ecu issues talk about P2073 Suction fan motor/air conditioning code?

It's communicating with the ECU and each module fine, no mention of any ECU, fan fault or otherwise?...

Here's the faults, obviously some may be historic, I've cleared them all from the system and going to take it for a spin and see which ones come back.

C1012 terminal 87 has over voltage
C1022 CAN bus fault
C1100 left front speed sensor
C1149 voltage supply of comp b24/2 esp lateral acc sensor
C1140 N49 steering angle sensor
C1141 Pressure sensor

Still none the wiser regarding my fan issue 😕
 
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Daveedge

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C32 AMG
🤣😂😁
Right we have a conclusion..

Basically each time I fitted a part I didn't want to take it for a drive because of the potential overheating issue so instead used the a/c function as a way to determine if the fan was working or not...

The problem is I now know that the A/C isn't working properly because of the condenser/no refrigerant..

I cleared the codes took it out for a drive and there was no coolant visit workshop or any other malfunction.

Pulled on the drive ano heard the distinct sound of a fan 😁🤣

Soo the fan issue has been fixed but it could have been either the fan, module or coolant temp sensor.

I'm assuming all the esp faults were due to the battery being disconnected.

Very happy and it drives faultless.

Thanks for all the replies and suggestions 👍
 

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