Is it the battery?

[Chrisdmm]

Hi Guys,

I'm hoping I can get some answers from those who've had issues with the charging system in their 911s. I have an 88' 911 3.2 and its been giving me issues that I haven't been able to figure out yet.

It started in the summer when my voltage would spike to 16-17 causing all my electronics to get wacky and light up (seatbelt light, radio on/off, dimming lights). I ordered a new VR and put that in myself. Everything was fine for about 2-3 months. I even bought a digital voltage meter to put in the cig lighter so that I can keep tabs on whats going on.

As of about 2 week ago I started getting lower than normal voltage while driving (11-12 volts, 2000-5000rpm, no difference), clearly the car was running on just the battery. Again, seatbelt light would blink once in awhile and headlights would dim, charging light in the cluster would blink like there was a bad connection. Checked bulb and connection at the cluster, no problems found.

I came to the decision that it must be the alternator going bad, after all it is the original one. Last week I had a new one installed by a very reputable shop here in Jersey, they checked all connections and the car drove great all weekend after the install. Volts were in the 13.5-14 range, no issues.

Tuesday I went to start the car, digital meter showed volts at 10-11 with the car on at idle and at 2000+ rpms, cluster light was rapidly blinking, alternator wasn't charging, looked exactly like the situation before the new alt was installed. Didn't feel comfortable driving it, parked it in the garage and plugged the Battery Tender in.

Today I went to start the car so that I can take it back to the shop to have them look at it again. I unplugged the battery tender, saw the light was green meaning the battery was fully charged, started the car and guess what...12.5 with the car off and 13.5-14 volts with the car on.

Sorry to make this longer than it has to, but now I'm confused as to whats going on here. Could it just be a bad battery or do I have an alien car?

Thanks,

Chris

[S2GART]

I vote for alien possessed......

How old is the battery? Are your grounds good?

When I replaced my VR for similar symptoms, once I started the car, the volts read 17 Volts. Had the alternator checked out and it was perfect. The shop suggested that I check all the grounds. When I put the alternator back in, I wire brushed/steel wool all the connections dealing with the installation of the alternator. With it all together, she started and was fine.

[wwest]

Clean/burnish all battery posts/connections/grounds and check the connection at the starter solenoid to the alternator output.

[911pcars]

Originally Posted by Chrisdmm

Hi Guys,

I'm hoping I can get some answers from those who've had issues with the charging system in their 911s. I have an 88' 911 3.2 and its been giving me issues that I haven't been able to figure out yet.

It started in the summer when my voltage would spike to 16-17 causing all my electronics to get wacky and light up (seatbelt light, radio on/off, dimming lights). I ordered a new VR and put that in myself. Everything was fine for about 2-3 months. I even bought a digital voltage meter to put in the cig lighter so that I can keep tabs on whats going on.

As of about 2 week ago I started getting lower than normal voltage while driving (11-12 volts, 2000-5000rpm, no difference), clearly the car was running on just the battery. Again, seatbelt light would blink once in awhile and headlights would dim, charging light in the cluster would blink like there was a bad connection. Checked bulb and connection at the cluster, no problems found.

I came to the decision that it must be the alternator going bad, after all it is the original one. Last week I had a new one installed by a very reputable shop here in Jersey, they checked all connections and the car drove great all weekend after the install. Volts were in the 13.5-14 range, no issues.

Tuesday I went to start the car, digital meter showed volts at 10-11 with the car on at idle and at 2000+ rpms, cluster light was rapidly blinking, alternator wasn't charging, looked exactly like the situation before the new alt was installed. Didn't feel comfortable driving it, parked it in the garage and plugged the Battery Tender in.

Today I went to start the car so that I can take it back to the shop to have them look at it again. I unplugged the battery tender, saw the light was green meaning the battery was fully charged, started the car and guess what...12.5 with the car off and 13.5-14 volts with the car on.

Sorry to make this longer than it has to, but now I'm confused as to whats going on here. Could it just be a bad battery or do I have an alien car?

Thanks,

Chris

Sounds like an intermittent open circuit (broken wire or connection) somewhere. Could try moving accessible parts of the harness around while engine is running and observing the multimeter display. Was there previous collision damage to the vehicle?

Perhaps a friendly electric shop can put the alternator on their test bench and with your harness installed (that possible?) try to simulate the symptoms you have. That might help isolate the location of the electrical issue (harness, alternator, regulator or ??).

Or you could simply bypass the normal diagnostic steps and start buying replacement parts and hope for the best. However, buying essentially spare parts can get expensive.

At some point in time, it might be good to surrender to an experienced electrical tech to find and fix it. Sometimes, the trick is find one (a good tech).

Sherwood

[Norm Faustino]

+1 on the grounds.
I had a bad ground on my E30 beemer and it wasn't that technologically advanced but it turned out to be the cause of everything from heavy shuddering at idle to all kinds of mystery gremlins. Then the car completely died one night on the way home. I had no power to crank and the hazard blinkers had barely enough power but after fumbling around a bit, I FOUND IT! The engine ground was completely loose. after I tightened it back on everything worked flawlessly.

[Bob Kontak]

Originally Posted by Chrisdmm

I unplugged the battery tender, saw the light was green meaning the battery was fully charged, started the car and guess what...12.5 with the car off and 13.5-14 volts with the car on.

Fully charged battery after immediate un-plug from battery charger will be in the high 12's - e.g., 12.8-ish. Try this again but give it a half hour for voltage to settle down.

Also, what that wwest guys says makes sense.

[Chrisdmm]

Thanks guys.

I will take the battery out and thoroughly clean the terminals + get it tested.

What are the most important grounding points I should check/clean?

[kidrock]

Originally Posted by Chrisdmm

Thanks guys.

I will take the battery out and thoroughly clean the terminals + get it tested.

What are the most important grounding points I should check/clean?

Battery to body ground inside driver's fender; transaxle to chassis ground underneath car @ driver's side of transaxle; and ground cluster @ #1 intake.

Also, I'm curious if anybody cleaned or tampered with the alternator to engine ground strap when doing the alt/VR repairs?