Car has come back worse than before

jayjay21

Recently took my car to a local garage for some general work which included removing my tow bar, as it was damaged and I have no intention of using it.

The car is fitted with parking sensors and worked perfectly before being taken in, when I collected the car the tow bar was removed but the sensors no longer worked.

They had the car for another day, but when I went to collect it, they told me that they did not know what was wrong and I had to take it somewhere else to be repaired, despite it being fine beforehand.

Do you think I am within my rights to take it back and ask them to get it fixed/fix it themselves?

AdrianC

Reversing sensors are often wired to the towbar wiring, if it was properly fitted, to prevent them being over-eager when you have a trailer connected. It's probably just a very simple connection needing re-making.

Joe_Horner

Are they original or aftermarket sensors?

The aftermarket ones normally have two connections: one earth and one connection to the reversing lights. If you had a 12 S (7 pin grey) or a 13 pin socket on the tow bar then anyone fitting aftermarket sensors would normally tap into the reverse light connection to the socket because it avoids taking another tap from the main car wiring. As Adrian as said, in this case it's almost certain that one or both have been disconnected.

If the sensors are OEM integrated ones then they tend to be under ECU control and it's far more likely to be coincidence rather than anything to do with the tow bar being removed.

AdrianC

Joe_Horner wrote: »

If the sensors are OEM integrated ones then they tend to be under ECU control and it's far more likely to be coincidence rather than anything to do with the tow bar being removed.

Unless the body computer needs to be told, on a dealer computer, that the towbar's gone. But I'd have thought that'd lob up various fault codes and/or error messages.

Joe_Horner

Agreed, and there's no technical reason why it should need to be told - there's no practical difference between a tow bar socket that's removed or just not got a trailer plugged into it and, on a standard socket, no way for the car to know either way.

Of course, that doesn't mean the makers haven't done something non-standard just for the fun of it!

AdrianC

Joe_Horner wrote: »

Agreed, and there's no technical reason why it should need to be told - there's no practical difference between a tow bar socket that's removed or just not got a trailer plugged into it and, on a standard socket, no way for the car to know either way.

There may be. There may be some sensor earthed when there's nothing plugged in, and open-circuit when there is. If that's now open-circuit... Alternatively, they may have incorrectly earthed something that only gets earthed when there's a trailer connected.

A half-way competent auto-electrician should sort it in seconds flat.

Joe_Horner

Yeah, but that comes under "makers doing something non-standard" (and pointless).

There may be reasons for the car to sense whether a trailer is connected or not - trailer indicator warning or even adjusting engine / ABS / traction control parameters - but I can't think of a single advantage to knowing if a tow bar is physically there or not other than to complicate things for the sake of it.

Like i said, that doesn't mean they won't do it :beer:

AdrianC

It's a legal requirement for any car to "know" when there's a trailer connected and warn the driver, audibly or visibly if the trailer indicators aren't working.

Also, it's common for reversing sensors (and sometimes rear fog lights) to not operate if there's a trailer connected.

Joe_Horner

Again, agreed. But that means sensing whether something's plugged into the socket, no whether the socket is physically there or not. If it's not there then, as far as any of those functions are concerned, it's exactly the same as having it fitted but no trailer attached.

AdrianC

Joe_Horner wrote: »

Again, agreed. But that means sensing whether something's plugged into the socket, no whether the socket is physically there or not. If it's not there then, as far as any of those functions are concerned, it's exactly the same as having it fitted but no trailer attached.

It's going to use earth or lack-of-earth to sense, right? So all it takes is that one little wire to have been wrongly earthed or left dangling...

colino

What kind of car is it and what was the damage to the towbar? Physical damage may have affected the PDC sensors, wiring or ecu; the removal may have screwed up the wiring, or it may well indeed need a quick session on a model specific diagnostic to switch the system back on properly.