Typically the ECU can handle 15-16 volts without immediate damage. There are
regulated circuits inside but the injectors and some other stuff uses
straight battery voltage. All VWs have the alternators running ~13.8 volts.
This voltage is chosen as it gives a good compromise for battery charging as
it is just at the edge of "gassing" the battery. Lower voltage leads to
sulphation and incomplete charging. Higher voltages can lead to corrosion of
the positive plates and excessive gassing during longer trips.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
neil n
Sent: Friday, November 20, 2009 4:33 PM
To: vanagon@GERRY.VANAGON.COM
Subject: How many volts can ECU handle?

Hi all.

Although I rebuilt the wiper linkages/shafts not long before swapping
engines, (Jetta 2.0) and it may be that they are simply working as
designed, my wipers have always seemed pretty "fast" since the engine
swap. Like fast enough that putting them on high, is kinda scary! (I
notice it more now as I tended to drive my Westy in Spring/Summer)
This lead me to thinking: "maybe my alternator is putting out too many
volts?"

Seems to me that the principals of Jetta and WBX ECU's should be the
same in this regard, so.....

Looking at my Vanagon Bentley, I see B+ from alternator going to the
Digifant control unit relay, then off to the Digifant ECU. Seems to me
that the amount of volts to the Digifant ECU is controlled only by the
alternator regulator. (or is there some other limiting component in
the ECU relay?)

More a point of curiosity than anything, but if an alternator puts out
too many volts, would this do any damage to an ECU? I figure that
things like wiper motors etc. can handle a little more, but was
curious about a more sensitive item like the ECU.

Either way, I should test alternator output.

Neil.

--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"

http://tubaneil.googlepages.com/

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engine
s