Hi all, I can't get my convertible roof to work and am not very good with electrics so would appreciate some help. As best I can I have checked things out. Relays seem new, earths are good fuse ok switch working. The only thing left I can think of is the handbrake. The return spring is off at the moment but in either position on/ off the parking brake light on the dash does not come on. I have checked the micro switch for continuity and it seems ok? Both the wires get 11.8 volts if I earth them when the ignition is on. I have swapped them around but no different. I press the roof switch and nothing. What should I check or do next. Thanks

 

Brinny
I know sod-all about convertibles, but my handbrake microswitch has three wires, one to each terminal. Are you missing one? if so I think it is the earth.

 

Cheers greg that could be it.

 

This is for a 95 but could be the same for you:

 

Well despite Greg's well pointed out missing earth it was not the answer. I have fitted the earth and done some basic tests, hopefully someone with more knowledge of electrics can help. Despite fitting the missing earth no matter where I grounded the micro switch wires did the handbrake warning light come on. I'm presuming a bad bulb because both the wires had nearly 12 volts with the ignition on. I tried the switch and that had about 5 volts on 2 terminals. I moved across to the wiring near the pump. The black and white wire going into a plug we discussed previously had 12 volts both sides of it as did the fuse. The relays seem ok and got 12v also.This brought me to the last few inches of cable to the pump in the picture. The brown and blue wires going to the fuse had 12v as did the other wires nearby. However while going into the loom all had 12 v the blue wire coming out in the picture was dead. This goes directly to the pump. What next? Suggestions please. Bit wary of electrics.

 

Here is wiring color codes to help and the complete conv top circuit.
The blue wire wire you speak about with the white plug/connector appears to be the Conv top motor connector. One wire should be Blue(U) and Black(B) and the other should be Blue(U) and Purple(P). One is power and the other is ground when commanded one direction, e.g, down, then reverses polarity when commanded the other direction. When not being commanded or at rest, both are going to ground through the at-rest positions of their respective relays. See diagram. You did check the main 30 amp fuse, correct?..not just the thermal fuses. The thermal fuses are for the quarter windows only. They provide the "stop" limit for those windows.

 

Ah, now it makes a bit more sense. Yes they are the wires going to the motor. I didn’t have the switch on when I tested them so they will have been at the at rest position. I will try again later. If all is working upto there then they should work when commanded? Main fuse was ok.

 

Ok, that's good that the main 30 amp fuse is ok. That means all the 12V sides of the relay for control should be good.

What the park brake switch does is "arm" the control box. After the control box is armed, it can now accept commands from the conv top switch to the relays. You'll see two inputs (grounds) from the conv top switch. Depending on the switch position, the ground is fed to one or the other input wire. One input wire is to command up and the other is for down. The control box then sends output grounds to meet their associated relays. For the top motor, one leg will need to be in the ground position through its at-rest position relay while the commanded ground leg activates the other relay in response to the selected conv top switch position. That will then provide the 12V power leg needed for the top motor.

If you just want to test the top motor operation, unplug the white connector and place 12V on one wire and ground on the other on the motor side of the plug. Motor should run in one direction. Then reverse the power and ground and do the same thing. The motor should spin the other way. This is how the motor spins the pump in the up and down positions. This way you will know if the motor is good.. Then just troubleshoot for the proper grounds getting to the relays.

 

Carsnplanes thankyou very much for your time and help with this. The good news is I have managed to get it working this morning!! After your post pointing out how the system works and with Greg's good spot of my missing earth it got me thinking. The fact the polarity reverses was a new concept to me but was the answer. It meant all was good so either the motor was shot or something else was wrong. Anyway my suspicion was the micro switch and sure enough it was . I jammed a screwdriver in to make sure the contact was made and tried again. Everything worked immediately. The parking brake light lit up , problem solved. I have now managed to re align my windows and get them all working and get the hood and rear windows working all of which I thought was beyond me. This has all been because of the fantastic help from the forum. All it's going to cost me is a new micro switch instead of an auto electricians bill. Once again thanks to carsnplanes for your detailed assistance and greg for his eagle eye. Thanks also to all the other contributors it feels good to have won one !!

 

Really well done Brinny. Part of the journey with an XJS is being brave enough to tackle stuff that scares you. We have all been there, and we all still face it from time to time.

 

Glad to hear it Brinny! Agree with Greg. It also helps to have the right tools/wiring to know how things are connected and why.