I work in product design for one of our nation's largest auto insurers, so I thought I'd take a stab at this one.
First off, yes, the Amex coverage is secondary to your primary insurance but if you have no primary insurance Amex becomes primary.
You did not say what the cause of your rental ding was. In many cases, if it was not your fault (e.g. done in a shopping center car park by a driver whom you did not see) then you can claim on your personal insurance under comprehensive coverage. The claims you want to avoid are collision coverages (overturn, moving accident w/ another driver involved, running off the road, etc) because they can, in some states that allow it, raise your insurance rates. Comprehensive claims do not work this way.
Talk to your insurance company and tell them about your accident. They will probably be miffed that you didn't notify them immediately of any loss but there is paperwork you can fill out to get around this. If you explain your circumstances they'll understand (at least they should understand!).
As far as Amex not covering your claim because you used coupons, you would have to read the contract for their insurance to determine whether you are eligible for benefits or not. Unless they specifically excluded coupon use, you might be able to argue that they should cover you.
I'd call your insurance company and spell things out, a good claims rep could certainly be of use to you here.
Originally Posted by zakami
I guess I learnt the hard way. I had a big dent on a rental car and filed a claim through the credit card I reserved and paid on (SPG AMEX). I had some free rental day coupons from Hertz and used them to pay for the rentals days, so the only charge that went on the AMEX was the $12 facility charges (rented at SFO). I got a ltter back from AMEX insurance stating that my claim to cover the car is denied because I did not pay for the rental FULLY on the credit card but used coupons to pay for it.
So if this happens to someone else in the future, I'd say do not turn in the coupons/free rentals days when you return the car if there has been damage to the car. My bill from Hertz is for $760, so not terrible but I sure would have liked AMEX to pickup the tab. I would have been out around $80 as compared to $760 if I had paid attention to the AMEX policy in advance.
I did call AMEX to argue but was told to call back during a weekday. I don't see myself having much luck winning this argument as I did use those rental days and their policy does state that the rental must be paid in FULL on the AMEX. If someone does have any ideas that would help, I sure am open to suggestions.