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Heater problems

l.chadburn

l.chadburn

New member
I have had my heater CCU repaired in the US and it has just been returned in working order with a life time guarantee.

I plugged it in the car and it now lights up as expected, only I still have the same problem.

WHAT DO I CHECK NEXT.

When I turn the ignition on I get front and rear fans on, on full and cannot change that.
When I turn the ignition off and pull the key out it carries on and i have to full fuse 1 to stop them.

Lee
 
Lee,

I can't recall if we have covered this suggestion before so I apologise if I'm repeating it, but your symptoms sound very much like the action of the NTC sensor in the rear blower plenum having gone bad.

The purpose of the sensor is to monitor the temperature of the air coming from the engine. If the temperature is above a defined level (as detected by the NTC sensor) it informs the CCU to maintain air flow over the engine by running the rear blower (and, possibly, the cabin fans) for some 20 minutes whereupon the temperature is sampled again.

If the NTC sensor is continually telling the CCU that the engine is over temp, your symptoms seems to be exactly what would happen.

Any chance of an update on who did the CCU repair (and the cost , if poss)??

Regards

Dave
 
Have you tried that second hand final stage relay yet? I watched unit 11 fix a car that had exactly the same symptoms. Changing the final stage relay fixed it.
 
Steve

Just fitted the other final stage relay that I had.

Made no difference what so ever.

either thats faulty as well or where do I go from here? any ideas

lee
 
Dave

I have also replaced the NTC sensor with a new one - no change.

I had the unit repaired by auto & truck electronics (autoecu.com) in the US.

It cost me $389 (£261) for the refurb plus postage there which was around £24.

I did get stung with import VAT and parcel force release fee (total £61) - am trying to claim the VAT back as it is a return package.

It also comes with a life time guarantee.

lee
 
Lee,

The thing that's confusing me about the symptoms is the fact that you get BOTH the rear blower and the cabin fans coming on together. One or the other is easier to diagnose and both my and Steve's suggestions would have covered those possibilities. With both coming on though makes the diagnosis somewhat more difficult.

If we assume that the CCU is now OK maybe we should turn our thinking to what legitimate cause could result in both fans operating. There's not much that I can think of that could be considered common ground to be honest. Something like a jammed open diverter valve (in the rear wheel wells) is unlikely to make the blowers come on. The temperature sensor in the CCU - I assume that was checked out when it was tested. There are no relays that are common to both front and rear blowers so no go there.

Try taking out the relay for the rear blower and see if the cabin blowers still start up. It's possible that if the rear blower runs, the cabin blowers might follow (bit of a guess here). If you disconnect the final stage amp (to stop the cabin blowers) does the rear blower still start up??

Do all of your flap servos operate as expected?? I'm running out of questions!!

Tell us some of the answers - it might get us somewhere.

Regards

Dave
 
Hi dave

just had a go at a few things you have suggested...so here goes.

with fuse 1 in

I removed the final stage relay - turned on the ignition = rear blower blows on its own. Have to remove fuse 1 to get it to stop
I then removed rear blower relay - turned on the ignition = front fans blow on their own. again have to remove fuse 1 to get them to stop.

I cannot control the speed or direction of air from the CCU.

I cannot see that any of the servos move under the bonnet.

What other things can I try? or do I now need someone to look at it?

lee
 
Hi steve

Unfortunately not had the time to do any work on it yet with work, christenings and kids. lol

Still thinking about taking you up on your offer if it still stands, just need to find some spare time.

Lee
 
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