grounding problem

[nuge]

Hi i have a problem with my 1995 crown vic hope you can help. when i park it over nite my battery goes dead and i got to give it a jump to get it started the next day. Its a new battery i just got . i think there is a ground some where. any suggestions where i should look for a ground. Any help would be great. Thanking you in advance nuge

[rhandwor]

Pull the negative battery terminal place a volt meter between the ground wire and neg. battery terminal. If you have over 25 milli amps 100 minute battery it is to much. Remember you have to wait to for the under dash lights to go out. Pull one fuse at a time until you find one which stops the excessive draw. If still their after all fuses blowed disconnect the alternator. Then start pulling relays one at a time. Older cars pull external regulator.
When you find the area start pulling bulbs or other items on the circuit.

[nuge]

thank you rhandwor wil try what you told me and will get back to you thanks again

[nuge]

Hi rhandwor done like you said but i never got mV on meter it showed 12 volts did i do something wrong. dont know much about those meters. placed one end on ground and one on post (neg) 12 volts came up on meter. done this several times same reading nuge

[mechhound]

I'm not sure how you did it but you have to remove the negative battery cable from the battery post and then connect the meter between the bare negative battery post and the loose cable end that would go on the battery.

[rhandwor]

You are checking for amperage draw not volts.

[nuge]

hi mechhound thats the way i did it but i never got mVon my meter i got 12.5 volts. thanks for the response nuge

[nuge]

thats what i did wrong will try again thank you

[nuge]

hi rhandwor its me again im getting 0.01 0.02 amps showing on the meter is this good or bad. nuge

[Selectron]

0.02 Amps (that's 20 milli-amps) is a perfectly reasonable quiescent current drain, so your problem is elsewhere - either the battery itself, or the charging circuit - that's the alternator, the voltage regulator, and the associated wiring connecting those items to the battery.

After leaving the car standing overnight, I'd measure the voltage next morning prior to starting the engine - you should expect to see at least 12.6V (this tells us that the car does not have excessive quiescent current drain, but we already know that because you measured it), then after starting the engine, measure the voltage again and it should read thirteen-point-something volts, possibly as high as fourteen volts (this tells us that the battery is receiving charging current from the alternator). Then rev the engine a little and that should rise to around 14.2V and stabilise at that level (probably somewhere between 14.2 and 14.6 volts - this tells us that the voltage regulator is working correctly).

If one or more of those measurements aren't as expected then that will tell you where to start looking for the fault. If however they all give normal readings, then the battery itself would be suspect.

As for 'quiescent' current drain (I'm an electronics engineer, by the way) - that is the residual current which continues to flow after the ignition has been switched off - it's a low-level current which runs the clock, retains the radio memory and onboard computer memory, and powers the alarm circuit. I'm not familiar with your vehicle (I'm in the UK and we don't have them over here) but I found a photo of one and it's a fairly big car so I'll guess it has at least a 60Ah battery fitted, and that would happily cope with a 20mA quiescent current drain if left parked for a couple of weeks or more and I would still expect it to start readily, so something is causing your battery to not receive, or not maintain, a full charge. Start by taking the voltage readings above and that will hopefully be a pointer in the direction of the fault. Oh yes, and when you're taking the voltage readings, be sure to make contact directly with the lead battery posts - don't measure at the connectors, because that would hide a high-resistance connection between connector and terminal post, so that's why you need to measure directly on the lead post.

[Selectron]

I was just thinking about that 20mA - that may not be the real quiescent current drain - it depends under what conditions you measured it. So to get an accurate indication of the overnight current drain, if the alarm would normally be set then you would need to attach your meter (set to measure current flow from negative terminal connector to negative terminal post) and then close all doors and activate the alarm. Then give it maybe a minute for everything to settle down and that would then be an accurate quiescent current reading (I'll just mention in passing that my Escort 1.8 diesel estate has a current drain of 35mA when parked, and with the alarm activated).

[nuge]

thanks for the information selectron the reason i think i have a ground is. if i take the neg cable of the battery post and leave it over nite when i hook it up the next day its starts fine so it cant be the battery. i just bought the battery its a heavy duty one because the car has power locks windows seats etc. it also has air ride . i think its going to be hard to find a ground. i was hoping someone knew an easy way so i dont have to trace the wires thats a big chore. thanks again nuge

[sheebeehuh]

You mentioned your car has rear air suspension (RAS). It's a long shot but it could be an air leak in the RAS system causing the compressor to cycle too often (or run too long) and thus killing the battery over time.

Just a thought.

[Selectron]

If the battery is too flat to start the car after being left parked overnight with the battery connected, but it will start the car ok after being left overnight with the battery not connected, then the current drain of whatever is causing the problem must be fairly high. I'd be thinking in terms of one of the lighting circuits - glove box light, trunk light, under-hood light, etc., so check if these all switch off when they are supposed to.

If they all appear to be in order then I'd move on to measuring the quiescent current - disconnect the battery negative lead and then connect a multimeter set to the current (amps) range, between the negative connector and the negative terminal post. Then close all doors and set the alarm and then watch and wait until the current reading rises to a higher-than-normal level. If all is well, then the current should only be a few tens of milli-amps, say 0.03A or so, but if the fault condition occurs then it will probably rise to around 1A or more, and you can then check visually to see if any of the dash lights or other lighting circuits are illuminated.

The other way to track it down would be by leaving the battery connected overnight but pulling different fuses each night until you find the offending circuit by a process of elimination. That could be a slow process though, and if it were me I'd go by the current measurement method.

If the car is parked on your driveway or in your garage and you can leave the meter hooked in circuit then I'd set it up to read the current and then check it at 30 minute intervals. Obviously if your parking is on-street then that won't be practical and you'd have to use the fuse-pulling method.

Here are some old threads which refer to the same problem - overnight battery drain on the Crown Victoria:


http://www.automotiveforums.com/vbul...d.php?t=493750
http://www.automotiveforums.com/vbul...d.php?t=212348
http://www.automotiveforums.com/vbul...d.php?t=416898
http://www.automotiveforums.com/vbul...d.php?t=571390

Edit: Just another thought - you said that's a new battery, so I'm wondering what happened to the old one - are you sure that the charging circuit is working correctly? Perhaps the battery is not receiving a full charge and is therefore operating right on the borderline, and leaving it parked overnight even with just a normal current drain (i.e. no fault condition) is enough to mean that it won't start next morning.

As a rough-and-ready check, start the engine and measure the voltage directly on the lead terminal posts (not the connectors) and note the voltage, and then rev the engine a little and note the voltage again. For the first reading you should get thirteen-point-something volts and for the second reading you should get around 14.2V and it should stabilise at that level regardless of engine speed, as the voltage regulator kicks in.

If that checks out ok then the charging circuit is probably working normally and you can then concentrate on tracking down the excessive current drain.

[rhandwor]

After you shut it off a relay can stick but not 100% of the time. Listen for a fuel pump running or other relay uses.