Electical and intermittent starting issue
05-06-2016, 06:49 PM
#1
2nd Gear
Thread Starter
Join Date: May 2016
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Electical and intermittent starting issue
1988 944 NA, 61,000 miles, in-between one to twenty minutes of run time the red service light and check oil light comes on, temp gauge goes to the top and jumps around, alternator gauge drops below 12, oil pressure gauge drops from 4.8 to 2.0., if the car is turned off then back on the battery performs as if it is low (cranks as if it is drained). However, if the neg. battery cable is disconnected and then reconnect it resets. Battery/starting and gauges all perform as normal until the malfunctioning cycle begins again? The car runs fine mechanically during these malfunctioning episodes and the battery test good. Has anyone experienced this or have any suggestion? Thanks.
05-07-2016, 09:06 PM
#2
Rennlist Member
Erratic gauges and false high/low indications are often caused by poor grounds, suspect wiring/connections, and/or additional resistance/corrosion. Electrical issues manifest themselves in many, strange, inexplicable, ways.
When your problem re-surfaces and the electrical system indicates less than 12v, put a VM across the battery terminals while the engine is running to confirm the actual state of the system. If the battery measures 13.5v +/-0.4v, I would look into poor/compromised grounds, wiring, and connections.
When your problem re-surfaces and the electrical system indicates less than 12v, put a VM across the battery terminals while the engine is running to confirm the actual state of the system. If the battery measures 13.5v +/-0.4v, I would look into poor/compromised grounds, wiring, and connections.
05-09-2016, 11:35 PM
#3
Second the ground check. Just be careful when checking the battery cable ground on the block. You can and will drop the bolt into the flywheel if you don't cover up the suspiciously placed sight hole right below it. Ask me how I know..
05-19-2016, 11:39 PM
#4
Burning Brakes
Clue: You disconnected the negative terminal, the only part that has an electrical connection that was disturbed. Sounds like voltage drop gets higher when the bad connection heats up (causes higher resistance). Does it do the same thing if you disconnect the positive battery lug?
Check/clean the heavy wire going the negative battery lug that goes on the battery terminal (wouldn't hurt to do the positive also). You might have to replace it. Some of the smaller wires that have ring lugs on them also get corroded under the crimp. Replace with new ones, and solder them if you can. I have even seen where the nut and washers get oxidized and make poor connection.
Electrical wasn't Porsche's finest moment!
Check/clean the heavy wire going the negative battery lug that goes on the battery terminal (wouldn't hurt to do the positive also). You might have to replace it. Some of the smaller wires that have ring lugs on them also get corroded under the crimp. Replace with new ones, and solder them if you can. I have even seen where the nut and washers get oxidized and make poor connection.
Electrical wasn't Porsche's finest moment!
