Newbie 964 DIY Questions

[RandyF]

After several years of 911 SC ownership, I've purchased a 1990 964, and I'm now ready to do some basic DIY projects. I've already tackled an exhaust vibration problem, as I replaced three of the four bolts that connected the cat converter to the heat exchangers. I can only guess how they broke, but it sounds much better now.

First question is; what are the appropriate jacking points for a 964? The manual states that only specified points on the bottom of the body should be used. I ended up jacking the car up at the middle ridge of the engine and then lowering it down on two jack stands I located at the recommended rear jack locations. Jacking the car up by the engine would be typical on a 911 SC, but is there a better way to do it on a 964 with average home garage floor jack and stands?

Second question is regarding the battery. I've noticed that the battery discharges in about five days if I don't drive it around a bit. One of the first things I did was have the previous non original Sony radio head replaced by a newer Sony unit. I heard something about replacing the radio with a non stock unit can cause a battery drain. Is this true, and is there a work around to prevent this? There is no working alarm on this car as far as I can tell.

I'll stop at those two questions for now, although I've got plenty more. I'm pretty happy with my 964 so far, as it handles and performs better than my SC, although it doesn't seem to rev as freely.

Thanks and happy driving!

[aigel]

The way to find the drain is to measure current at the battery while you start pulling fuses. Once you know which circuit pulls your battery dry. You take it from there, disconnecting possible offending devices. You should be able to find information on hunting down a battery drain independent from the marque of the car.

Jacking up by the engine remains a good point on the later cars. I find it hard on my 993 to use the jacking points, as I have the jack on there and then no place to put the jackstand.

George

[colo964]

Look for a green wire in the radio "socket". It is part of the OEM alarm and should be taped off with non-OEM radios.

Even with that fix, I notice that my battery drains in 2 weeks, unless I pull the fuse to the radio when parking it at the airport for more than 2 weeks. I thought it was my amp, but turns out to be my Harman Kardon headunit.

Jacking: For a lot of stuff, ramps work pretty well. Otherwise, you're doing it just fine.

[RandyF]

Thanks for the feedback guys. I'm glad to hear that others jack up 964's by their engines without causing damage. Using ramps when possible makes sense too.

I'll look for the green wire when I get the opportunity, but as battery drain seems pretty common on 964s, I'll continue with my practice of driving it once or twice a week and putting the battery on slow charge when I've ignored it for too long.

The above described way of locating a current drain works. I have lifted my '91 C2 for years by the engine and no issues...

my $0.02

-CKKrause

[bigchillcar]

+1

[daven5735]

I too have a '91 and have already gone through the learning curve with the battery drain problem. After driving myself crazy with going through every possible circuit and testing at the battery for any measurable drain, I decided to do the following: I went to every switch that contolled a light....hood light switch, engine compartment light switch and door switches for interior light. First, the hood light switch mounting bracket was bent just enough so that when the hood was closed, it still didn't depress the switch button enough to completely break the circuit. So I bent it back into place. The other switches had enough corrosion so I replaced them all. That and some fresh bulbs and problem solved. Just to make sure, I also keep a BatteryMinder (model 12112) plugged-in. A Battery Tender will also work great. They both come with a plug/pigtail that you install on your battery and leave it. Then you simply connect/disconnect at the plug connector and you're ready to go. The key here is that these are battery maintainers, not high-amp chargers.

Dave
'91 C2
S&W 45

[bigchillcar]

i've seen the same thing on my hood light..closing, but not turning off!

[RandyF]

Thanks for the updates, they give me some things to look for. So far I've seen two things on my car that cause the battery to drain in short order: 1) the turn signal will sometimes stick, 2) the passenger window switch sometimes remains switched in the up position. I've had both put enough drain on the battery so that it won't start after eight hours or so. If I make sure neither of those two things occur, I'm good for about a week. I have a practically new battery too, as I thought that might be the problem.

I'll try the technique of systematically removing fuses sometime. Hopefully I can detect the difference with my inexpensive meter.

As far as charging the battery, I've just been giving it a two amp overnight charge from my charger if I haven't driven it for awhile. Does the BatteryMinder just plug into the cigarette lighter (instead of the battery terminals)? Does it stop charging when the battery is fully charged? Those things would make it a worthwhile investment.

Thanks,

[daven5735]

It has a "pigtail" that connects to the battery. You leave it there permanently. The other end has a simple two-lead plug that connects/disconnects to a mating plug that connects to the BatteryMinder. When you first plug it in it begins providing a trickle charge to the battery until it is fully charged. Then it automatically cuts off until it detects the slightest drain, then it turns on the trickle again. It does this repeatedly and keeps the battery at its peak. It's safe to leave it connected year round. I actually have a larger, more powerful version on my boat that keeps three batteries fully charged in the same manner. All batteries have a life but the Blue Top Optimas on my boat lasted over 5 years before I replaced them two years ago with three more. Over time even a fully charged battery will only be able to stay at an adequately performing level for a short time. The $40 or $50 for a good battery maintainer is well worth it. Hope this helps.

Dave
'91 C2
S&W 45
'99 Sea Ray 310 Sundancer

[tbennett017]

I was going to add that I bought an Optima Yellow top for this reason.. it can withstand more discharging and recover better due to its design. The model 35 fits the 964 perfectly.

Not the cheapest battery, but its closed design won't outgas into the trunk either.

[bigchillcar]

i've gotta buy an optima next..

[Tom W]

Optima batteries do not charge well with a simple tender (low current). The tender keeps them from discharging but the Optimas need high current to charge (I spent months with a drain issue and Optima red tops). I used a Sears tender that was connected to the battery permanently (like Dave's). You can get the kind that plug into the lighter socket too if that would work better for you. My issues were with the track car, so I got tired of the drain and charge problems and simply started using the electrical kill switch to disconnect the battery when the car sat (not the best for a street car because you'll likely loose the radio stations ... it will not hurt the car).

It's not always a switch or the radio green wire. In my case it was a relay that had intermitent issues.

www.p-car.com is a great site for DIY info. While mostly for 993s, the info is usually directly applicable to the 964.

Adrian's 964 book is a good resource to have if you do much DIY work.