Anyone else having trouble with those pesky heated mirrors? Judging from this forum and others they rarely work and my 2.5 TD is no exception.
However, help is at hand. Here’s a method of repairing them rather than taking out a second mortgage to buy new glasses.
Firstly remove the glass from the wing mirror. Look carefully below the glass roughly in the middle. In the small gap between the bottom of the glass and the plastic mirror housing you will see a tiny glimpse of metal. This is the wire spring which keeps the glass in place. Using a small screwdriver or toothpick push the metal spring to the side towards the car and at the same time push away from you. This will unhook the spring and with a few taps the glass will fall out into your hands. Disconnect the two connectors very carefully. Do not force them otherwise the solder tags will detach from the glass and will make you swear.
Next, put the glass in the oven at gas mark 1 ( or 100 degrees centigrade) and cook for 30 minutes. Take the glass out of the oven and before it has a chance to cool, slowly peel the plastic backing off the glass. It is held in place with a double sided sticky pad the same size and shape as the glass. Peel slowly and carefully. The resistance wire which does the heating is sandwiched between the sticky pad and the back of the glass. You may have to use the back of a spoon or a wooden lollypop stick to help prise the backing off the glass.
Once separated it is clear to see why the circuit fails. The resistance wire is very, very fine gauge copper. For most of its length it is trapped between the sticky pad and the glass and is protected from the elements by virtue of the waterproof pad. However, the resistance wire is not wound carefully and some loops are too long, passing outside the protective pad. These loops are subject to all the weather that the door mirror assembly is exposed to. The ends of the loops corrode and eventually break. With the circuit broken the heating element no longer works. In addition the two ends of the resistance wire pass out through a hole in the plastic backing and are soldered to a couple of solder tags. The tags are crimped to the plastic backing for strength and support. The hole in the backing where the two ends come out is another place where the weather gets to the wire and corrodes it.
Inspect the resistance wire under a strong light. You may even need a magnifying glass. The breaks are hard to spot. Once you identify a broken loop use a pair of tweezers or small long nosed pliers to pull some slack free of the sticky pad. Do this for both ends of the broken loop. The wire is varnished so before you can solder it you need to remove the varnish. I trapped the wire ends between my finger and a piece of ‘Wet & Dry’ (very fine) sandpaper. Pull on the wire and let it slide between your finger and the sandpaper. Repeat several times until the purple varnish disappears and is replaced by the gold coloured copper. Do this for both ends that you intend to join. Twist the wires together. Solder to make a good joint. Repeat this procedure for all of the loops which are broken.
If the wire is broken at the solder tags you will need to use the sandpaper to clean the tags. I found that the flux in the solder wouldn’t clean the tags.
Once you think you have repaired all the broken loops test for a complete circuit by connecting a multimeter set for OHMs across the solder tags. If you’re lucky, you’ll get a reading. If not, check for more broken loops. It can take a while.
Once repaired, my completed circuit measured 11 ohms.
To reassemble the glass and backing, smear Evo-Stick or a similar contact adhesive to the back side of the glass only. Wait until it dries and then stick the glass and the plastic backing together. Seal around the edge of the glass with silicone sealant. Also seal the hole where the two solder tags are mounted.
To replace the glass on the car, replace the metal spring. Put the end, bent at 90 degrees, into the hole for the purpose. It’s just off-centre at the bottom. Thread the spring around the circumference making sure it sits in the slots in the hexagon. Hook the looped end over the little plastic hook. Present the glass to the door mirror. Re-connect the two spade connectors, it doesn’t matter which is which. Offer the hexagon to the mating part on the mirror and push. The spring will clip over the mating part and stop the glass from falling out.
Hey presto – one working heated mirror.
For anyone who has heaters that currently work, I would suggest that you take out the glasses and seal around the perimeter and the connector hole with silicone sealant before the damage is done.
Best of luck
norrie
Those pesky heated mirrors on an XM
Moderator: RichardW