Ok, sorry that did not work
I'll go through what I know and hopefully something will work.
The wipers and washers should be on the same fuse so its unlikely to be a fuse issue. Only other thing on switches could be the connector block.
As Helz says it is worth checking the rear contacts. Check that they are clean and that the springs are ok. Check that the rear door closes properly. Check behind the trims on door and body as you can get corrosion and/or loose connections. Finally check the earth connection, left rear.
If you can get a spare battery or a meter, try putting a direct feed onto the motor or measure its winding resistance. Rear wipers on early models tend to fail a lot.
Front wiper. Check earth, left front. Check connections at motor/plug and inspect the loom for wear, etc. as far as possible. Again if you can, put a direct feed on the wiper to see if it works at both speeds.
Thats about as far as I can help you. The wipers are connected directly through the switches. If the wipers work with a temp feed then it is likely that the switches or through connections are gone. Rear wiper failure and rear door connections are fairly common faults. I'm not aware of any major electrical issues with front wipers.
Good luck and let us know how you get on