Hi all,
2006 4.2 Coupe @ 91k miles
I had a completely dead car the other day, and to cut a long story short, installed a brand new battery.
It appears the previous battery died because of a small fan constantly (24 hours) switching on and off every 15 seconds or so - with a cold engine and car locked. it's situated under the RH headlamp, and occasionally the fan runs for a good 3-4 minutes, and yes, it's draining the battery.
I'm led to believe it's an 'auxiliary air pump' (dealer's words, not mine). I'll try to post a video.
Has anyone met this problem before, or know exactly what it is, and why it should be running like this? I'm guessing it's a sensor gone bad, but any help would be greatly appreciated!
Cheers, Mark

 

Welcome to the forums Mark,

Your post was automatically locked for moderation. I can't see any problem with the content and have unlocked it.

Graham

 

I have never heard of this, nor seen the fan mentioned. Under the headlight, as in Remove the Headlight Assembly and it is beneath that, inside the bumper cover?

 

Hi CJ,
I've never heard of it either :-(
Yes, the offending unit is inside the bumper immediately under the RH headlight. The fan itself isn't visible, but it's definitely in there.
I can't find anything obvious in the 4000 page workshop manual, mainly because I don't know what the unit does or what it relates to. The only thing that is remotely similar is on the air intake side (page 1809 diagram) but I can't see it needing a fan.
Very frustrating!!
Mark

 

Are you talking about the secondary air injection unit? Being in Europe, your vehicle should have it installed.

Sounds like an electrical issue so I would disconnect the battery, then disconnect all the electrical connectors to the pump and valve (if the valve has an electrical connector), and clean them out. Not sure if there is a module or fuse for the pump/valve, but I would check those out too. If that doesn't work, could be an internal short in the pump. Heres the procedure to remove it ...

 

Is this is?





Graham

 

Thanks for your replies chaps - they've been a big help.
Having browsed the workshop manual once again (thanks for pointing me in the right direction!) yes, that seems to be the culprit. I'll check the hoses for leaks, then the pump connectors, to see why it appears to be on a constant leak test cycle.
I must admit I didn't know this secondary air pump existed, but in mitigation I haven't had the car long - despite having Jags most of my driving life!

Mark

 

Ok, I’ll bite. ‘What’ is the secondary air injection pump. Why doesn’t every xk have one?

 

I don't know if/why every XK doesn't have one, but this is what the workshop manual says:

Secondary Air Injection (SAI) is fitted to the vehicle to reduce exhaust emissions to meet European Union (EU) Stage 4 and Federal Petrol Emission standards.
The SAI system comprises: • SAI pump • SAI valve • Associated pipes • SAI Absolute Pressure (MAP) sensor (NAS only)
The SAI pump is used to provide a supply of air into the exhaust manifolds during the cold start period of the engine. The SAI cycle lasts for up to 65 seconds. The hot unburnt fuel particles leaving the combustion chamber mix with the air injected into the exhaust manifolds and immediately combust.

My mysterious problem seems to have cured itself, so maybe there was some moisture lurking somewhere. I'm keeping an eye on matters, and carrying a battery booster with me!

Mark