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Discussion Starter #1
Hi guys,

I have a 2008 CRD SRT Design and recently I've been having some problems with the voltage dropping on idle when the inside heater blower is on and the radiator fan kicks in.

With the blower off, car idles fine and voltage remains at 14.6-14.8V.
When I turn the blower on the voltage holds but the car seems to idle a bit rougher. I feel stronger and uneven vibrations on the steering wheel. When the radiator fan comes on the voltage drops to 13.5V and the interior lights dim. This only lasts half a second and once the fan has started voltage goes up and the lights are fine but the car still idles a bit rougher than without the blower.

I couldn't get the car to behave the same way with the blower off. I tried turning everything on (rear window heating, mygig, etc.) but the car idles fine whether the radiator fan is on or not.

The only other thing I noticed is that when any of the turn signals is on while idling the voltage fluctuates from 14.4V to 14.8V. I guess that's because of rapid load changes not giving the alternator time to adjust its output.

Does it look like a faulty blower motor or the alternator not being able to produce enough power for 2 very power-hungry fans?

Thanks for your help!
 

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When the cabin heater is first turned on there are Electric Heaters on the CRD because the engine on diesels are so slow to warm up. So rather than it being the fan, it is more likely to be the electrical load placed on the system by the Electric Heaters.

Only a guess. It could be proven by pulling fuses for the Electric Heater but I wouldn't be overly concerned about it to be honest. Having said that I've never noticed it affect mine.

EDIT
Sorry didn't read your post correct. Not an initial start up problem.
The rad fan does draw a fair whack of current. How often does your RAD fan run. Mine hardly ever runs.
Dont suppose the Electric cabin heaters are on all the time for some reason ?
Don't think the Blower Fan alone should draw that much current. It shouldnt load the system that much.

Now the Electric heaters (There are 3 elements) are fused at 50 AMP each which if they are on all the time is anything up to 150 Amps which is a high load on the system.

Jack
 

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Discussion Starter #3 (Edited)
When I idle it's usually in city traffic where engine temp is higher and rad fan comes on often.
The voltage drop usually happens every 0.5 - 1 minute. Always at around 190F-192F which is the temp thermostat opens (I assume fan comes on at the same time?).
The problem never occurs when the engine is below the operating temp.
The engine doesn't run cold or hot. The needle always stays just under half-way mark. In traffic the temp can go up to 210F, but in motion doesn't seem to ever exceed 197F.


EDIT
I'll try pulling the fuses for the heaters. So these heaters would normally come on only when cold? I guess they shouldn't turn on if the blower temp is set to the lowest setting?
My problem happens even if the temp knobs are all the way to the left (min setting).

Oh and just to confirm, there are no error codes.
 

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The electric heaters should really only operate on a cold engine.
The extra load may be nothing to be concerned about because no fuses have blown.

When loading an engine up by electrical equipment the load can sometimes affect the engine at idle.

I think the only way to identify the problem would be to use a clip on ammeter to measure the current drawn by the suspect electrical bits.
The Rad fans are a hefty beasts and even if bearings are perfectly free will load the engine up. Rad fans do fail and get stiff bearings though and it may be worth while feeling how free they spin by hand.
The Blower fan may just take the combination current just a bit high but the real culprit could be the Rad fan, especially as you say prob only when engine up to temp.

jack
 

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Also understand that if the HVAC system is in a bi-level or defrost mode, the HVAC compressor will engage, creating both an electrical load and a mechanical load on the engine. RPM's will slow a bit, idle may roughen up and due to the lower RPM the alternator output will fluctuate as the compressor engages and disengages.
 
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