PRND selector fault - Only goes forward

[Flying John]

An embarrassing moment today when I came to select reverse the Blingo just went forward. Thats odd I thought and went through all selections hoping to see the reverse yellow light come up on the dash. But it only lit when I selected Park. I had to wiggle it around so that it was just out of Park (so the pawl wasnt engaged) and still giving some reverse. Got out of trouble and decided I needed to strip down the selector to see whats what.

After removing the trim round the handbrake and the selector lever you can undo 4 small machine screws on the side of the selector lever and open up the hole where the business end of the selector is.

This appears to be a simple mechanical link to the Park pawl and a black device mounted on the drivers side with two wires leading to a small plug. It would seem that as you move the selector what you are really doing is changing the resistance of a two connector pottentiometer. One end is connected to 12 volts from (I guess) the ECU and as you move the selector this voltage rises and falls as more (or less) resistance to ground is in circuit.


This "pot" measure 200 ohms to 2Kohms from end to end. It seemed to adjust smoothly and vary the voltage on the line back to the ECU - but alas no reverse.

Anyone experience anything similar - all help appreciated.

John

[Flying John]

Well after a longer than expected day with my diagnostic hat on I have discovered and fixed this problem and thought others may like to know what the fault was.

As I said in the 1st posting - I could not initially select reverse and I was able to start (clunk) in any gear position.

I stripped out the trims round the handbrake and the gear selector and there is a single plug with 4 wires. Two of the wires are for the green LED that glows under the PRND legends and the other two wires go to the ECU (pins 53 and 55 i think).

When I ,measured the voltage it was ranging between bout 5.5v and 12.2 volts depending where the selector was.

I plugged in the diagnostic Actia kit and this said there was a fault of a short circuit to 12volts on the selector line.

I connected up a spare potentiometer to the two wires and found that if I could get the voltage down to 3volts or thereabouts the selector seemed to work. Now on the diagnostic kit both the accelerator pedal voltage and the gear selector voltage field is marked at 5volts. So how come I had 12v.

I dug out the French Berlingo book and on page 93 there was a diagram of the selector and the 4 positions of the lever. This showed that there should be 0.9 volts for Park, 1.7volts for R, 2.5 for N and 3.3v for Drive. So now I understood the fault report of 12volt short to selector line on the Actia.

So where was this 12volts coming from. I disconnected the large multiway connector from the right side of the controller and a residual voltage remained. Tracing the wires thru there are two large dirty brown round screw in connectors on the nearside just under the little black box with the one fuse on top.

I opened the one nearest the front of the van and the lowest 4 connectors had so much green gunge round them you could have planted a potato

So a squirt of toluene and a brush out followed by a few puffs of compressed air saw all the gunge gone.

I reconnected and it all worked perfectly.

Hope it helps someone else.

John

[ChrisB]

Nice one, so I presume water must have been getting into that connector and tracking accross or was it a earthing issue due you think and it was getting this stray voltage via something else ?

ChrisB

[Flying John]

I think it is an adjacent pin/pins carrying 12v that was leaking across through the jelly like crud in the connector Chris