Question I have a 1990 Alfa Romeo Spider Graduate Spider, my fourth Alfa Spider. Since I purchased the car in 1994, with 25k and like new condition, I have experienced problems when using the wipers and heating fan at the same time. If my headlights are on, I have actually had the wipers stall while driving and at idle. The alternator was replaced a couple of years ago with a like new one from a wrecked 1991 Spider with less than 10k. My battery is an orange top Optima.
Using a good voltmeter, at idle I have 14.2 volts measured at a junction of large red leads under the hood. At the battery in the trunk I get 13.8 . At the cigarette lighter I get 13.7 (I measured there because it was easy.)
The lighter is on the same circuit as the wipers and heater fan which seems to be fed thru the contacts of the ignition switch in the on position. I have the factory 1990 specific shop manual.
At idle, if I turn on the heater fan the voltage under the hood at the junction drops only slightly to 14.15 but at the the cigarette lighter it drops to about 13.2 If I add the wipers the voltage at the lighter may drop to 12.7 or lower while I still have 14.1 under the hood. If I turn on other items I can easily drive the voltage at the lighter contact to below 12 volts while having 14 volts at the red leads under the hood, and 13.6 to 13.8 at the battery.
I have cleaned all the grounds that I can find and all the connections appear good. Do you think the ignition switch is the problem? If so, how has it lasted all these years without getting too much worse? If the ignition switch contacts are causing the problem, are there any modifications that might help (1) prevent the failure of a new switch and (2) make sure that full voltage is available to everything fed thru this switch?
Charles
AnswerI am impressed with your ability to trouble shoot the
electrics properly. There is a permanent solution.
Put the battery lead at the switch to two (2) 30 amp
relays and have them activated by the ignition switch.
Divide up the consumers between the 2 relays. The relays
must have surge suppression on the coil terminals (terminals
86 [plus] and 85 [minus]). The Bosch relays with the red
strip have this suppression. Also, many American Auto
applications have the same.
You must also check the amperage draw of the wiper motor
and the fan motor. The main problem is that too much draw
must go through the switch, but, a consumer could also
be aggravating the problem.
If you need more detail, I will oblige
