relays

Paul,
If I'm not mistaken, relays are pretty straight forward, they either work or they don't. Automotive relays are of an 'enlargement' type, e.g., to control a high power circuit w/a low power 'branch' curcuit. With DC electrics, wire sizing is based on the amt. of power (in watts) required @ business end of the ckt.. Relays reduce the need to carry large amts. of power thru-out the total ckt., including controls (switches, etc.) thereby reducing costs & increasing effectiveness. Swapping out 'like kind' relays is an easy way to determine if the relay is functioning properly. Yes, you can check your relays w/a multimeter but it's not going to give you a % health reading, and it's rather involved.
Bruce

 

There are only two different types of relays among the 20 relays in my 400i, so it is easy to swap a couple of like relays to see if that fixes the problem in the questionable circuit (and cause a similar problem in the swapped circuit if the first relay really is bad), even if you don't have a spare. The relays are readily available and not very expensive, so keeping a spare of each is probably a smart idea. Even if you don't carry spares and one craps out on the road somewhere, you can usually swap the failed relay for a critical system (e.g. fuel pump) for one from a non-essential system (e.g. the horn or the high beams) in order to make it home.

Also, keeping the contacts clean and tight can make a huge difference in the performance of the relays.

John

 

What kind of relays does the 400 use? The typical Bosch type? These are only like $5 a piece....
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I have been thru this problem. Like all Ferrari owners of a certain age (the cars I mean).

My advice is. If in doubt about a relay replace with a new one. I believe Bosch dont make these relays anymore and the manufacturing rights has been taken over by Tyco of Portugal. If you are buying Bosch you are buying old stock.

Secondly I would use a quality electrical contact cleaner on the connections on the fuseboard and when replacing relays or fuses use a product called Stabilant on the contacts (see other threads in this forum about this product) which acts like a solder but is a NATO approved substance which remains viscous on the contacts.

A good winter project is to clean electical contacts in the fuse board area and coat fuse and relay pins with Stabilant.

Hope this help

 

Right, this is also what I've experienced with the fuse board. Murphy's law would be : the fan fuses contacts will stop making contact the day you' re stuck in a traffic jam. Fan fuses are at the center of the left board.