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Help to diagnose C Max fault


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Hi all,

My girlfriend has a 2005 plate Ford C Max, very low mileage (16k) due to first owner being elderly, full service history and well maintained. 10 days ago she heard a loud screeching sound coming from the engine and managed to get it home, next day engine cut out and would not restart. RAC recovered the car and diagnosed a problem with the starter motor which had now blown. 

Car recovered to a local garage (RAC recommended) who agreed starter motor is the issue but also needs a new power cable. Total work including labour £355 (a little steep I thought but thats by the by). The work took 4 days to complete due to parts availability. Car drives home fine after collection in the evening but next morning, same problem... RAC recover again and diagnose starter motor and power cable blown out once more. After some to do with the garage the mechanic reluctantly accepts liability for the blown parts on the basis he clearly did not fix the actual problem. Agrees to replace parts under warranty and continue to look for the fault.

Now here is our problem, this was now 5 days ago, and still no fault found. He has disconnected new starter motor and using a test light which seems to be working fine. He claims to have got it to fault once, but not for long enough to diagnose the issue. Without finding the fault he doesn't want to release the car and have to accept liability for blown parts again (understandable) however my girlfriend is currently paying £30 in taxis per day to get to work which is unsustainable until the garage happens to come across the fault.

So what is reasonable here? How long should the garage continue to test before trying alternative means (not sure what these might be)? For the car experts among you, any suggestions on what the fault could be?

We have suggested that the garage quote us for replacement of all parts in the circuit (to my knowledge this is starter motor, power cable which have both been done, plus ignition switch and relay). Garage doesn't want to just throw parts at it which is understandable, but on the basis the two parts left are relatively inexpensive it seems like an acceptable option.

Of course we could take it to another garage but RAC wont recover it again on the basis they have taken it to a suitable location. So we would bare the recovery costs plus lose warranty/goodwill from this garage and have to start again..

Thoughts and advice appreciated!

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Engine cut out came both times a while after starting so leads me to believe this isn't an ignition problem. Garage and RAC suggested screeching noise is the starter motor but I would assume that this would also cut out upon ignition, and not continue running while driving.

Garage still unable to diagnose or find fault

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2 hours ago, Walshy252 said:

Engine cut out came both times a while after starting so leads me to believe this isn't an ignition problem. Garage and RAC suggested screeching noise is the starter motor but I would assume that this would also cut out upon ignition,

This is frustrating, and looks to be more complex that first envisaged.

The exact point when the screeching started is important. If it is while driving, some time after any start attempt, then I have some difficulty seeing it is the starter motor. The coil for the starter relay (Start lock relay) has one side to the ignition switch (start position) and one side to the pcm (engine computer). So for this relay at activate, both the pcm must allow it, AND the ignition switch has to be in start. In am pretty certain the pcm side is de-activated as soon as the engine fires up, and only re-activated once the ignition is cycled off & on. If my car stalls, the key won't re-start it unless cycled off.

The only ways I can see the starter engaging while driving is either a very unusual fault in the relay, where it closes without being energised, or a wiring loom fault that supplies power direct to the starter solenoid, by-passing the relay.

There is another possibility. The same power cable for the starter goes to the alternator. Certain alternator or charging system faults might be able to blow the fusible link section of this cable. For instance if the alternator ramped up to full power output (full field strength) at highish rpm, delivering massive current to the battery. This would also overload the drive belt, and could make that squeal.

(Most of this info is based on the Focus wiring diagram, but the C-Max is based on the Focus, and this is very basic stuff.)

I would guess the old starter has been returned for exchange, so can not be tested. But the new one has not blown, if I read it right, although the power cable has gone again.

Of course, if the screeching started immediately after any starting operation, then that makes a sticking starter motor, or welded relay contact, much more likely.

I have some (small) sympathy for the garage, but perhaps they should have done more diagnosis and asked more questions before just assuming a faulty starter motor. A courtesy car would be a very useful offer from them, though as they are probably losing money on this job by now, they would not be very happy. You might need to try the iron fist in the velvet glove approach, promising future custom if all ends well, with well veiled promises of trouble if they don't help.


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Thanks Peter.

Garage have been less than helpful and have dragged out. Refused a courtesy car and not given us any confidence that they have the skill or equipment to diagnose this issue properly.

We complained to RAC and demanded they recover the car and tow to a new garage on the basis they made a poor recommendation initially. It is now with an electrical specialist who has charged £40 for diagnostic. They are suggesting based on description of symptoms that it is not an ignition issue but that is yet to be seen

Will update asap

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how long ago did you buy the car, and where did you buy it from?


Really, I would be looking to get the car replaced nad costs recovered from the initial salesman if it was done within the last 6 months!

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