Sigh.. Unusual FBH problem..

T16 · 25th February 2013, 19:31

So, before I drive my car off a cliff, with me in it, I was hoping some clever person might be able to shed some light on my FBH problem.

Quick summary..

Fitted brand new FBH to car that didnt have one.
Brand new Doser pump
Brand new loom at the front as the wires on the old one were worn through
Brand new LandRover temperature sensor (the more accurate version)

So... all was well until recently it just stopped working.

It tests ok by shorting pin 3, so fair enough. I replaced the temperature sensor as I expected it to be that, no difference.

Shorting the plug that goes onto the sensor doesnt turn it on either.

Ive checked the loom plug, and the loom around the drivers side headlight, and it all looks 100% ok.

Is there some place in the engine bay that the loom by the drivers headlight might have a problem?

I really dont know what else to troubleshoot, and have really reached the end of my patience with the MG.

Has anyone had this sort of error before?

suffolk boy · 25th February 2013, 20:09

ok seems like you have covered most bases.so back to the begining .the fbh.you say it is new?unlikely unless you shelled out over £500 for a new one.if you did send it back pronto.in the meantime if it worked with the new temp sensor.and was all tickety boo .it points out to your pcb is cream crackered,

T16 · 25th February 2013, 20:19

Yeah, it was off a guy called Roverbreakers.

A few forum members bought some new FBH's off him a few years ago.

He had some more relatively recently.

As far as I could see it was unmarked, and looked totally new.

I thought a faulty PCB meant that it would not start and run at all? I dont get any strange behaviour when opening and closing the car doors.

It works great when its pin3 to ground!

Greeners · 25th February 2013, 20:31

You need to check the wire from the sensor with a metre that you are getting 12v with the engine running and the outside temperature is 5 degrees or below.(or unplug the sensor and bridge the 2 pins)

If not, check the alternator side of the sensor., if not it's the alternator output that's failed, or a break in the wiring

Thomas · 25th February 2013, 20:55

Moved to technical help forum

T16 · 25th February 2013, 21:33

Ok thanks.

What wires should the 12v be on at the FBH ??

I guess thats the easiest thing to check first.

Greeners · 25th February 2013, 21:39

Brown / Yellow is from the ECU / Alternator to one side of the temp sensor
Slate / Green from the other side of the sensor to Pin 1 on the FBH

oldcarguy · 25th February 2013, 21:57

Check the wire from the plug by the headlamp to the sensor, mine had been pinched behind the front panel and finally broke inside.

T16 · 26th February 2013, 16:37

Quote:

Originally Posted by oldcarguy

Check the wire from the plug by the headlamp to the sensor, mine had been pinched behind the front panel and finally broke inside.

yeah, thats what happened to mine, it had been rubbing on the intercooler.

I replace the loom that runs to the bonnetswitch, horn, and fbh sensor with a brand new one!

Thats why I am perplexed. All looks fine after inspection too. No breaks or anything.

Thats why I wondered where the loom went in the engine bay after the big grey plug under the headlight....

If I do not get 12v at the connector to the FBH, how on earth am I going to be able to troubleshoot the entire loom?

Is the alternator side of the loom easily accessible? Im not sure where it takes the power from for the sensor.. I thought it came all the way from the battery where the loom for the FBH plug is.....?

oldcarguy · 26th February 2013, 18:01

From the socket behind the headlamp the wire runs upto the ECU and is unlikey to be damaged, but you need to do a test to see if your getting voltage at the socket when the engine is running, as you get the signal from the alternator.

25th February 2013, 19:31	#1
T16 I really should get out more....... ZT CDTi 135, ZT260SE Join Date: Feb 2011 Location: Dundee Posts: 2,877 Thanks: 10 Thanked 331 Times in 213 Posts	Sigh.. Unusual FBH problem.. So, before I drive my car off a cliff, with me in it, I was hoping some clever person might be able to shed some light on my FBH problem. Quick summary.. Fitted brand new FBH to car that didnt have one. Brand new Doser pump Brand new loom at the front as the wires on the old one were worn through Brand new LandRover temperature sensor (the more accurate version) So... all was well until recently it just stopped working. It tests ok by shorting pin 3, so fair enough. I replaced the temperature sensor as I expected it to be that, no difference. Shorting the plug that goes onto the sensor doesnt turn it on either. Ive checked the loom plug, and the loom around the drivers side headlight, and it all looks 100% ok. Is there some place in the engine bay that the loom by the drivers headlight might have a problem? I really dont know what else to troubleshoot, and have really reached the end of my patience with the MG. Has anyone had this sort of error before?

25th February 2013, 20:09	#2
suffolk boy This is my second home fiat panda Join Date: Sep 2009 Location: haverhill Posts: 6,720 Thanks: 96 Thanked 586 Times in 526 Posts	ok seems like you have covered most bases.so back to the begining .the fbh.you say it is new?unlikely unless you shelled out over £500 for a new one.if you did send it back pronto.in the meantime if it worked with the new temp sensor.and was all tickety boo .it points out to your pcb is cream crackered, __________________ fiat panda 1.2 eco

25th February 2013, 20:31	#4
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	You need to check the wire from the sensor with a metre that you are getting 12v with the engine running and the outside temperature is 5 degrees or below.(or unplug the sensor and bridge the 2 pins) If not, check the alternator side of the sensor., if not it's the alternator output that's failed, or a break in the wiring __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

25th February 2013, 20:55	#5
Thomas This is my second home MG6 1.8T GT SE Join Date: Mar 2009 Location: Falkirk Posts: 9,510 Thanks: 106 Thanked 173 Times in 128 Posts	Moved to technical help forum __________________ MG6 1.8 TCi in Artic White 1975 Land Rover Series 3

25th February 2013, 21:39	#7
Greeners Moderator MG-ZTT Join Date: Mar 2007 Location: Ware, Herts Posts: 19,798 Thanks: 161 Thanked 1,249 Times in 1,036 Posts	Brown / Yellow is from the ECU / Alternator to one side of the temp sensor Slate / Green from the other side of the sensor to Pin 1 on the FBH __________________ *David* Impecunity is the mother of ingenuity Useful how to's for common problems Car Of The Month Jan 2014 [SatNav Power Down] [Coolant Level] [SatNav Repair] [Diesel Non Starting] [Paint Codes] [Rear Light Seals] [Reversing Light Switch] [Bleeding Brakes][Sunroof Drain] [Early ZT's][Instrument Pack Diagnostics][ATC Diagnostics]

25th February 2013, 20:19	#3
T16 I really should get out more....... ZT CDTi 135, ZT260SE Join Date: Feb 2011 Location: Dundee Posts: 2,877 Thanks: 10 Thanked 331 Times in 213 Posts	Yeah, it was off a guy called Roverbreakers. A few forum members bought some new FBH's off him a few years ago. He had some more relatively recently. As far as I could see it was unmarked, and looked totally new. I thought a faulty PCB meant that it would not start and run at all? I dont get any strange behaviour when opening and closing the car doors. It works great when its pin3 to ground!

25th February 2013, 21:33	#6
T16 I really should get out more....... ZT CDTi 135, ZT260SE Join Date: Feb 2011 Location: Dundee Posts: 2,877 Thanks: 10 Thanked 331 Times in 213 Posts	Ok thanks. What wires should the 12v be on at the FBH ?? I guess thats the easiest thing to check first.

25th February 2013, 21:57	#8
oldcarguy Posted a thing or two Rover 75 Conn SE Tourer Join Date: Aug 2011 Location: Driffield Posts: 1,952 Thanks: 27 Thanked 151 Times in 125 Posts	Check the wire from the plug by the headlamp to the sensor, mine had been pinched behind the front panel and finally broke inside.

26th February 2013, 18:01	#10
oldcarguy Posted a thing or two Rover 75 Conn SE Tourer Join Date: Aug 2011 Location: Driffield Posts: 1,952 Thanks: 27 Thanked 151 Times in 125 Posts	From the socket behind the headlamp the wire runs upto the ECU and is unlikey to be damaged, but you need to do a test to see if your getting voltage at the socket when the engine is running, as you get the signal from the alternator.