What is the normal drain on the battery when the Reatta is setting parked?
This question comes up quite often on the AACA Reatta forum. I will try to answer that question and show how to check the current draw on the battery in your Reatta.

You will need a multimeter capable of measuring voltage and amperage to perform this test. Leads for the meter with alligator clips will make the it easier to make connections but are not necessary. A 3/8" bolt screwed into the battery will also make it easier to connect the leads of your meter to the battery.

This test was performed on my 1988 model that only has factory accessories. The electrical system is in good condition and working properly. Amperage readings for other models may vary.

To check the battery drain properly you need to start with a fully charged battery. With mine fully charged it measured 12.6 volts.

Make sure the ignition key is in the off position and all lights and accessories are turned off. Do not turn them on during testing or attempt to start the car.

Disconnect the negative battery cable.

Connect the leads to your meter for measuring amperage and set the meter to the 10 amp scale.

Be certain you have your meter set correctly. Not doing so could destroy your meter and possibly do other damage!!

Connect one lead from the meter to the battery and the other to the disconnected battery cable as shown in the photo below.

battery_drain-1.jpg

When I first connected the leads, the meter read 4.40 amps.

battery_drain-2.jpg

After 5 seconds a click could be heard and the meter dropped to 4.31 amps.

battery_drain-3.jpg

After 60 seconds the meter reading dropped to 0.02 amps (20 milliamps) and stayed there as long as the meter was connected. If the meter was disconnected and then reconnected it would again read 4.40 amps and fall to 0.02 amps after 60 seconds.

battery_drain-4.jpg
 
The results of your test may vary some but this should give a good baseline if you are trying to determine if you have a short that is draining your battery.

AACA forum member Padgett wrote:
 
"GM spec is "less than 50 ma" The '88 which has no RKE will be the lowest, 17-20 ma in my experience. Anything over 200 ma will drain the battery in a day or two.

Also if your DMM is limited to a 10A max, when the blower module shorts so that the heater/ac fan is running constantly (not uncommon failure) , the draw can be in the neighborhood of 15 amps and will pop the fuse (if you have a fuse)."
Thanks to members of the AACA Reatta forum for this information.
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