How do I replace the electric aerial mast on a 2004 Volvo S40 4dr (older 2003 model shape) I have read that you just need to pull the old mast out and feed the cable through into the motor, swicth the radio off and it will feed the rest of the cable through? Is it really that easy?

It is usually best to check an aerial from the radio end with an ohmmeter or continuity checker. The aerial cable is a coaxial cable with a centre core that carries the signal and an outer braid that when properly grounded keeps interference to a minimum.

Measuring between the centre and the outer there should be an infinity reading on an ohmmeter, indicating no short circuits in the cable or aerial base. Measuring between the outer and a good ground the reading should be very low, no more than a few ohms indicating a good ground connection to the aerial base and of the aerial base to the bodywork.
The next test is simple and tricky at the same time as one lead of the meter will need extending. Remove the aerial mast and test for a very low reading of just 2 or 3 ohms between the cable centre and the stud or socket where the mast mounts. If all tests are fine it indicates the mast has an internal fault. If the tests aren't fine the cause is fairly intuitive.

To some extent you can perform the tests at the aerial base but the results will be limited due to the physical connection between the cable and aerial base won't be part of the test.

You need to be aware some installations are fitted with an aerial amplifier which can confuse matters and make checking more difficult.

Typically there are two ways: easy and major surgery. The easy way is available, depending on exactly how the old mast is broken....Car off, radio off, unscrew the external pieces of the antenna at the mount, right where it exits the vehicle...Have assistant turn on radio and activate the antenna. It should spit the whole mast and inner piece. The new one goes in, BUT BE ready to carefully and without kinks, feed the new mast assembly.
If this method does not work, you have to extract the entire motor assembly and open it up. Sometimes easier to replace the assembly.

well they are almost impossible to straighten without breaking most likely it will snap off and you may need to replace the whole auto antenna unit ( not to exppensive if you can fit it) best of luck you can try straighten it if you want.... best of luck p.s if you try straighten i would recommend using pliers to squeeze the antenna back into shape at the bottom of the bend just be careful not to squish it flat etc.....

Mercedes preferred supplier of aerial masts is Hirschmann. There is a connector to the top of the box a coax aerial connection to the mast root, an earth lead strap and a bolted bracket to the base. The aerial mast exits through the car skin in a rubber fitted sleeve. You say that you can hear the motor running but that the mast refuses to emerge. The beauty of Hirschmann is that their motor drive antenna assemblies are readily disassembled (and reassembled). You will need to take the mast assembly out of the vehicle; disconnect the wiring plug socket, remove the bracket bolt, earth strap and unscrew the coax cable connector. Pull the mast firmly down and out of the body work sleeve. The outer aerial mast is driven up by a toothed plastic flexible inner rod normally stored in a coil within the motor assembly. Remove the torx screw in the middle of the rounded end and separate the two halves. At the top is the electric motor set horizontally which drives a rubber belt to a helical drive immediately below it lying parallel. If this belt is broken this would give rise to the motor running but not engaging . The helical drive engages with the edge of the storage drum feeding out and retrieving the coiled rod to raise and lower the antenna. If the helical drive or the drum edge has missing teeth then the aerial cannot function. All these components can be be bought from Hirschmann spares or through your Mercedes dealer.

the antenna mast has a nylon cable attached to the end of it which goes into the electric motor that raises it and lowers the mast. This cable has snapped apart causing this problem. A new mast or antenna will be needed to repair this back to working condition

antenna mast is no good.. you can buy a mast and have it installed or buy a used antenna and have it installed im sure Elite foreign auto parts has only saab parts.. tested and used,

The antenna mast (multi segmented metal thing that retracts) probably has a bend/kink in it.  Lucky you if it does, because you can just replace the mast.  This is much easier than replacing the motor.  Do it soon to avoid burning out the motor, or unplug at the antenna motor if you are going to wait.
If the mast doesn't fix it, then it must be the motor, the dealer MAY be able to take back the mast if you keep the packaging,  they will NOT ever take back electrical components,  but the mast is just mechanical.  Anyway the mast shouldn't be more than $30-40, it's cheaper and easier than the motor.

If it makes a clicking sound when going up or if it is bent the aerial mast will need to be replaced, if there is no noise and it seams to work normally and just gets stuck then it needs cleaning. You can use wd40 and a cloth, with the aerial up, wipe upward (upward only, wiping down will push dirt into the mast and make it worse) spray the wd on the mast and the cloth and wipe upward, sent it down and repeat 2-3 times.

JPTCAT

Len-
The replacement only costs about $20. The dealer can also provide a replacement but it can cost upwards of $50+. Part number is 5035944.

The hardest part is removing the metal sleeve from the mast pole. Once you get this out, refit the new mast with the teeth so the motor will pull the new mast down when you turn the radio off. refit the 17mm nut on top of the mast and then turn the radio back on. It will click a few times and then be properly set.

Justin
Strictly Saab
Melbourne, FL