i seem 2 have a problem with me pup and car hes nearly 6 months, it started 2 happen about 2 month a go and not sure why as hes never had a bad experiance in it as i all ways take him to parks in it , hes only got to see the car harness and hides he sits on the back seat of a 3 door fiesta normally, he even wont go near the door of it , i have always lifted him and out and must admit hes getting a bit heavy .iv always bin happy telling him we going out with toys and treats but still the same and when we come home from any where hes really sulky and seems down and for got 2 mention hes a rottie. do u think i might need a bigger car or is it me

He is reaching the stage where EVERYTHING becomes scarey for a while. You have to ignore it as best you can until he realises it won't hurt ;) Instead of the harness could you try using a cage in the back? It'll mean putting down the back seat so that you can get a decent size one in, but he might just be feeling a bit restricted in the harness.

Prehaps the harness hurts him try taking him to the car without the harness just his lead and just sit with him untill hes calm then reward for good behaviour. If hes willing to go to the car minus the harness then another means of securing him is needed. hth