Convertible quarter windows inop
#1
Convertible quarter windows inop
I recently purchased a 1992 XJS V-12 Convertible and the quarter windows refuse to work. I have checked all the relays, the thermal breakers and replaced the hood control module. Still nothing. When I bought the car they were able to get the windows up and down by jumping them. I could simply install window switches but I’d rather have the system work as designed. I have checked the 30 amp fuse also. Holding the switch until the motor stops doesn’t help. The hood does go up and down as it is supposed to. Any help would be much appreciated.
Last edited by Tibbetts; 05-18-2019 at 09:10 PM. Reason: Add information
#3
#4
For the quarter rear windows to function (in a convertible), the parking brake is the key. When lowering the top, the parking brake has to be engaged. When raising the top back in place, the parking brake has to be engaged. The windows will not function without the parking brake set. I owned a 94 XJS convertible. Experienced the same issue.
#5
Tibbetts,
As you say that the hood is operating correctly, then the problem doesn't lie with the handbrake switch. The problem must lie in the relays, window motors, wiring to the motors or (unlikely) the hood ecu.
Are you checking the relays by reading voltage output when the hoos is being lowered? (Easier to test on the down cycle because of the time delay from the ecu on the Up cycle.) If not, then backprobe the output wire from the relay when the hood down switch is pressed. If you're reading voltage at that time, the problem must lie in the wiring to the motors or the motors themselves. You mentioned that the motors can be powered directly so that points to the wiring, if you've tested the relays correctly?
So, if you've got output voltage on the relays when the switch is pressed, remove the 1/4 trim panels and see if you're then getting voltage at the motor. If none there, it confirms the wiring problem.
Good luck
Paul
As you say that the hood is operating correctly, then the problem doesn't lie with the handbrake switch. The problem must lie in the relays, window motors, wiring to the motors or (unlikely) the hood ecu.
Are you checking the relays by reading voltage output when the hoos is being lowered? (Easier to test on the down cycle because of the time delay from the ecu on the Up cycle.) If not, then backprobe the output wire from the relay when the hood down switch is pressed. If you're reading voltage at that time, the problem must lie in the wiring to the motors or the motors themselves. You mentioned that the motors can be powered directly so that points to the wiring, if you've tested the relays correctly?
So, if you've got output voltage on the relays when the switch is pressed, remove the 1/4 trim panels and see if you're then getting voltage at the motor. If none there, it confirms the wiring problem.
Good luck
Paul
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Mac Allan (05-21-2019)
#7
I did some relay testing with a volt/ohm meter although I’m not convinced that my testing was conclusive. They did all click and each seemed to function properly when used in the hood up and down positions. It does seem like a relay related problem but it seems unlikely for all four window relays to fail.
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#9
If the top/windows have not be used often, it has been reported that the motors can get 'stuck' and there isn't enough current to get them going. However, when I've experienced that, it was one motor at a time. So I would focus making sure current is reaching the motors first.
Good luck
#10
Thank you so much, Paul. I have tested the relays to the best of my limited abilities. This seems like a relay related problem since the hood operates normally. Is there more electrical load on the window relays than the hood motor? It may be easiest to eliminate one possibility by replacing all relays. Hopefully before this drives me nuts.
#11
Thank you so much, Paul. I have tested the relays to the best of my limited abilities. This seems like a relay related problem since the hood operates normally. Is there more electrical load on the window relays than the hood motor? It may be easiest to eliminate one possibility by replacing all relays. Hopefully before this drives me nuts.
Next, I would remove one of your side trim panels and see if you are getting voltage at the motor. If you are, and you have a safe way of measuring current/amps I would then test that and see how much current is passing through the relay.
When I had a inoperable window, believe it or not, the fix was to tap on the motor while voltage was going to it. Viola! has worked fine every since. I also recall someone having those windows function once the side trim was removed and the weatherstrip was no longer putting pressure on the window.
#12
#13
The way the system is wired, going up, the current grounds through the down relay, and going down it grounds through the up relay. It grounds through the normally closed contact, and I have seen many relays that are dual rated: 30A for the normally open and 20A for the normally closed contacts. It grounds through the lower rated contacts and over time they burn and pit and can't conduct as much power as they should. I don't believe the hood circuit grounds through relays, but it's been a while since I looked at the circuit.
#18
#19
Thank you Paul,
i have just replaced all six relays with no results. Top goes up and down but still no movement of the windows. They both worked when I bought the car but they had to be jumped. Unfortunately I didn’t see how they did it but I know the motors and regulators work properly. I’m stumped. I’d like to try getting the, to work but don’t know which two points to jump. Any help will be appreciated.
thanks,
Tibbetts
i have just replaced all six relays with no results. Top goes up and down but still no movement of the windows. They both worked when I bought the car but they had to be jumped. Unfortunately I didn’t see how they did it but I know the motors and regulators work properly. I’m stumped. I’d like to try getting the, to work but don’t know which two points to jump. Any help will be appreciated.
thanks,
Tibbetts
#20
Attached is the circuit diagram for the 1992 convertible top. Since the top goes up and down, we know the switches are good. The power coming in through the thermal breakers is not fused. I would start by putting a probe into the relay socket on the black wire and then to a good ground on the body and make sure you have continuity. If that's good, then make a small jumper wire and bridge the relay socket terminals. For example, to make the right window go down you would join where the 30 and 87 pins of the relay go in, which is the green/brown wire and the green/red wire
Last edited by Jagboi64; 05-26-2019 at 10:50 PM.