Electric use pulling engine down

[DMaugle]

Got my '87 out of mothballs Saturday.  Battery dead, hadn't run since mid- January, no surprise there.  Jumped easily and took off for a re-charge, fuel, etc.  Nice day so it was a while till I hit the heat levers but once I did the engine almost cut out entirely.  Backed off the levers and full throttle again, similar issue when using the power windows.  Ideas anyone.  Thanks, DMaugle

[michael lang]

Seems to me based on that description a load test on the charging system  would be a logical place to start.

[ccm911]

Agreed.  How old is the battery? 

[DMaugle]

New one put in last autumn.  Ran fine up until I put it away mid-January (first salting). 

I will backtrack for a moment though.  I've had the car for 4+ years and never had a problem starting it, even in the dead of winter until last fall.  Last season I had a problem with the clock.  Was told I needed a new one.  None in stock so all was re-hooked up and the clock ran fine when the ignition was on and not at all when off and radio did not work (took a while to notice as I rarely listen to it).  Next time in the shop had the wires uncrossed and both clock and radio had power at proper times.  Shortly thereafter original battery died and was told I needed a new battery and had one put in.  I have a concern that there is some other draw on the system and I honestly question who to turn to as my current shop is well known to this community.

I appreciate your comments and look forward to a lasting solution.  Regards, DMaugle

[ccm911]

It is time to start methodically pulling fuses.  Start with the fuse for the clock, and then see what happens.  Obviously, you'll want to assure that the battery is fully charged prior to this exercise.  Also, try to follow as many wires as you can in order to assure that all is well.  Look for cracks or discoloration.  Pull one fuse each day or so.  Hopefully, you will then be able to isolate the troublesome circuit.  From there, it will be just a matter of checking everything on the circuit.

I'll almost bet the farm that there is something funky with your dash wiring.  The clock, the radio and the heater have all been involved thus far.  Pull the clock(and the radio if you could) and then shine a light in the recess behind the dash.  Does anything look disturbed?

You didn't by any chance just install a dead-pedal, did you?  I know from experience that you can hit the main power cable when drilling.  It runs right along where you need to drill.

Just be methodical, buy a Bentley manual, and you should be fine.  And as you rule out things, let us know.  I'll bet your solution will help a lot of folks in the future.

[DMaugle]

Thank you for the info, I was afraid I'd have my work cut out for me.  No to the dead-pedal btw.  Regards, DMaugle

[LouZ]

A quick way to isolate the circuit is to pull the cable from the battery. Then connect an ampmeter between the cable and the battery treminal. Read the amperage draw. By the way, the ref books should list the acceptable amp draw with the key off.

 

Shut the doors and hood so no lights are on. By the way, check that glove compartment light!

 

Next, pull 1 fuse at a time and check the amp draw, when it significantly drops, you have isolated the culprit circuit. Check what is attached to that particular fuse circuit, then troubleshoot those devices.

[michael lang]

Chris, those are great suggestions to DMaugle for a starting point. Especially the Bentley Manual. One of the best investments I've made into my car was getting that book. Very precise.

What we're overlooking here is a 20 yr old car, before I'd start isolating fuses and wiring possibilites I'd start with the alternator. A load test on the alternator might save alot of time chasing this problem.

DMaugle, just out of curiousity, what did the volt regulator show as a reading when you did the load test. If it's too low it is not recharging your car's battery. That means that ALL electrical components (fuel pump, ECU, etc...) the stuff you don't see & then there's the heater the radio the lights etc..., are all drawing power from your car battery when the engine is running. So when you use a window switch, or turn on the blower, use the wipers, whatever, they are overriding the other components that are using the available electricity. Try this as an excercise, fully charge up your car's battery. Then go drive it & use all the normal things you would use, windows, wipers, heater, radio. With the fully charged battery everything should work and there be no drain on the engine causing it to bog down. If this was a problem I was dealing with on my car, I'd start with the charging system first to make sure that all the electrical components are getting enough power to operate properly.

Good luck, please keep us posted.


 

[michael lang]

Sorry dude, I forgot to give you the spec.

Spec for a fully charged system is 12.6v, minimum is 12.0v that is for the battery.

To do a battery load test, apply 200amp load for 15 seconds. For this time of year (temperature) figure a passing reading would be 9.3-9.5v.

All this information can be found in section 270 of the Bentley Manual.

Again good luck