| Author | Message | |||
     Mark Aldridge Prolific User Username: mark_aldridge Post Number: 117 Registered: 10-2008 |
The windscreen washers work and the windscreen wipers work, but the wash wipe facility does not ! If the wash /wipe is operated ,only the washers work. Any suggestions please. The car is a 1987 Bentley 8, UK spec. chassis 22684 Thanks Mark | |||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 118 Registered: 10-2008 |
Just found an earlier posting on this problem,looks like another ECU is required! Mark | |||
| Graham Burn Experienced User Username: graham Post Number: 33 Registered: 6-2013 |
Hi Mark, several of the "ECU"'s fitted in our cars are little more than a control circuit operating a relay and very often all that's required is to clean the relay contacts, not sure if this applies to the wiper unit but when some of my interior lights ceased to come on when a door was opened this was the problem and other than a bit of time to take the unit out, open it up and clean said contacts cost nothing to fix  Graham | |||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2970 Registered: 4-2003 |
Graham, true, but more often then not a transistor or two inside the ECU is dud. Still very simple stuff and easily repaired. It is always a good thing to replace an aged transistor while you are at it regardless. RT. | |||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 128 Registered: 10-2008 |
I have replaced the two MPS6534 transisters with BC327, now the intermittent wipe does not work and neither does the wash wipe. I cannot find a replacement for the zenner diode (TO3C24 ) >Any suggestions ? Mark | |||
| Graham Burn Frequent User Username: graham Post Number: 54 Registered: 6-2013 |
Hi Mark, I found this information on zeners, don't know if it's of any help as I'm no expert on electronics!
Regards Graham | |||
| Peter Talbot Prolific User Username: squerryes Post Number: 191 Registered: 7-2010 |
Mark - try the sites below: www.mouser.com/Zener-Diodes www.nxp.com www.xxl-sale.co.uk/Zener-Diode Peter | |||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 129 Registered: 10-2008 |
Graham, Peter, Thanks for the help. I have ordered new semiconductors and will see if this sorts the problems. Mark | |||
| Peter Talbot Prolific User Username: squerryes Post Number: 193 Registered: 7-2010 |
Mark Just make sure you get the new Zener Diode the right way round !!!! Peter | |||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 161 Registered: 6-2005 |
Mark, Because both the washers and wiper work OK separately, the problem is likely to be the circuit that provides a delayed 12V from Terminal 2 of the Control Unit to energise Relay 3 which in turn switches 12V via Relay 1 to the slow speed brush of the wiper motor. The Wash/Wipe switch on the steering column provides an earth to energise the washer pump and an earth on the Light Green/Black wire connected to the Control Unit. This second earth energises the wiper motor. It is likely that this second earth is absent and it would have been better if this had been checked before changing electronic components. It is too easy to damage circuitry by changing components without good reason. John | |||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 130 Registered: 10-2008 |
Thanks John, I have an earth connection at terminal 2 when the washer is pressed, but I have less than 2 volts at terminal 2 at standby.This is what suggests that the control unit may be faulty. Mark | |||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 162 Registered: 6-2005 |
Mark, Fair enough. Because the circuit incorporates both ON and OFF delays you really need a circuit diagram (or draw one from the unit) to determine where the fault is. The voltages are odd. On standby Terminal 2 should be 0v via Relay 1 winding to ground, as the output transistor should be cut off. With the Wash/Wipe switch operated Terminal 2 should be 12V. Did you replace the transistor connected to Terminal 2 ? I see that the Control Unit (UD70070) is available on Ebay for around 65 GBP. Good luck. John | |||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 163 Registered: 6-2005 |
Mark, Both the Wash/Wipe and the Intermittent Wipe use the Control Unit to provide the necessary delays so they are both affected by the fault. Sometimes these old hand assembled circuit boards can have poor connections at the solder points on the back of the board so as a final resort I would use a soldering iron (preferably temperature controlled) to quickly melt the solder at each joint to repair any bad connection. John | |||
| Mark Aldridge Prolific User Username: mark_aldridge Post Number: 131 Registered: 10-2008 |
Gentlemen, success ! I replaced the transistors with identical units ;(new old stock on ebay),and Zenner and all now works. A worthwhile excercise and the total cost to replace all of the components on the board would have been about £5. This compares with approx £200 for a new unit. If changing the tansistors and zenner had not worked, I intended to change all of the components. Mark | |||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 164 Registered: 6-2005 |
Good work ! |
Zener