I'm having a problem with the battery draining when the Bronco sits overnight, even with a fully charged battery. The only thing I have changed recently is the fuel pump/sender assembly in the tank. Truck started strong in the garage after changing the pump, then the next day it was completely dead. Replaced with brand new battery and its still going dead. I don't know why the pump would drain the battery down? Should I check the relay or do you guys think the pump is causing the issue?
Battery drain when off
- Thread starter TheBus
- Start date
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yo,
Do you hear the fuel pumps running when engine is off and ign sw is off?
If so, do check FP relay. If good, check EEC relay,m because it may be hanging up or contacts stuck and signalling FP relay to close
Location pic; GREEN Connector pic, next to the Brown Connector Under hood behind air cleaner assy; pic in a 90 & up to 91; Miesk5 NOTE, Someone had removed those relays from the bracket
Source: by Need4racin (The 90 Bronco, Dean) at http://img130.imageshack.us/img130/9307/temp90pics033ru4.jpg
Wiring Diagram in 87-89 Bronco & F series (Mitchell)
Source: by equivalent (Beetlejuice) at SuperMotors.net
=============
If not;
Parasitic Current Drain Test; "...
Remove Negative the cable from Battery & place an ammeter in-line set to the 10A range.
Isolate circuit causing current drain by pulling out one fuse after another while reading the display.
Current reading will drop when the fuse on the bad circuit is pulled.
Reinstall fuse and test components (including connectors) of that circuit to find defective component(s).
Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp, or luggage compartment lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses or disconnecting fuse links to pinpoint the location of the current drain. When the current drain is found, the test lamp will go out or the meter reading will fall to an acceptable level. If the short is still not located, after checking all the fuses and fuse links, the drain may be due to the generator. The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (underhood, glove compartment, luggage compartment, etc.) that do not shut off properly. If the drain is not caused by a vehicle lamp, remove the fuses from the interior fuse junction panel, one at a time, until the cause of the drain is located. If drain is still undetermined, remove fuses one at a time at the main fuse junction panel to find the problem circuit. Check for current drains on the battery in excess of 50 mA with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure;
DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED. Do not crank the engine or operate accessories that draw more than 10A. You could blow the fuse in the meter. Many computers draw 10 mA or more continuously. Use Rotunda 88 Multimeter 105-R0053 or equivalent between the battery positive or negative post and its respective cable. NOTE: Steps 1-5 correspond to the numbers in the following illustration. Insert the test leads in the input terminals shown. Turn switch to mA/A DC. Disconnect battery terminal and touch probes as shown. Isolate circuit causing current drain by pulling out one fuse after another while reading the display. Current reading will drop when the fuse on the bad circuit is pulled. Reinstall fuse and test components (including connectors) of that circuit to find defective component(s)..." from 1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual;
Source: by Ford
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (underhood, glove compartment, luggage compartment, etc.) that do not shut off properly.
If the drain is not caused by a vehicle lamp, remove the fuses from the interior fuse junction panel, one at a time, until the cause of the drain is located. If drain is still undetermined, remove fuses one at a time at the main fuse junction panel to find the problem circuit.
Electronic Drains Which Shut Off When the Battery Cable Is Disconnected
Repeat Steps 1 through 6 of the voltmeter drain testing.
Without starting engine, turn ignition on for a moment and then off. If applicable, wait one minute for the illuminated entry lamps to turn off.
Connect the voltmeter and read the voltage.
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps after a few minutes, and if this drain did not show in previous tests, the drain is most likely caused by a malfunctioning electronic component. As in previous tests, remove the fuses in interior fuse junction panel one at a time to locate the problem circuit. .."
Do you hear the fuel pumps running when engine is off and ign sw is off?
If so, do check FP relay. If good, check EEC relay,m because it may be hanging up or contacts stuck and signalling FP relay to close
Location pic; GREEN Connector pic, next to the Brown Connector Under hood behind air cleaner assy; pic in a 90 & up to 91; Miesk5 NOTE, Someone had removed those relays from the bracket
Source: by Need4racin (The 90 Bronco, Dean) at http://img130.imageshack.us/img130/9307/temp90pics033ru4.jpg
Wiring Diagram in 87-89 Bronco & F series (Mitchell)
Source: by equivalent (Beetlejuice) at SuperMotors.net
=============
If not;
Parasitic Current Drain Test; "...
Remove Negative the cable from Battery & place an ammeter in-line set to the 10A range.
Isolate circuit causing current drain by pulling out one fuse after another while reading the display.
Current reading will drop when the fuse on the bad circuit is pulled.
Reinstall fuse and test components (including connectors) of that circuit to find defective component(s).
Typically, a drain of approximately one amp can be attributed to an engine compartment lamp, glove compartment lamp, or luggage compartment lamp staying on continually. Other component failures or wiring shorts may be located by selectively pulling fuses or disconnecting fuse links to pinpoint the location of the current drain. When the current drain is found, the test lamp will go out or the meter reading will fall to an acceptable level. If the short is still not located, after checking all the fuses and fuse links, the drain may be due to the generator. The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (underhood, glove compartment, luggage compartment, etc.) that do not shut off properly. If the drain is not caused by a vehicle lamp, remove the fuses from the interior fuse junction panel, one at a time, until the cause of the drain is located. If drain is still undetermined, remove fuses one at a time at the main fuse junction panel to find the problem circuit. Check for current drains on the battery in excess of 50 mA with all the electrical accessories off and the vehicle at rest. Current drains can be tested with the following procedure;
DO NOT ATTEMPT THIS TEST ON A LEAD-ACID BATTERY THAT HAS RECENTLY BEEN RECHARGED. Do not crank the engine or operate accessories that draw more than 10A. You could blow the fuse in the meter. Many computers draw 10 mA or more continuously. Use Rotunda 88 Multimeter 105-R0053 or equivalent between the battery positive or negative post and its respective cable. NOTE: Steps 1-5 correspond to the numbers in the following illustration. Insert the test leads in the input terminals shown. Turn switch to mA/A DC. Disconnect battery terminal and touch probes as shown. Isolate circuit causing current drain by pulling out one fuse after another while reading the display. Current reading will drop when the fuse on the bad circuit is pulled. Reinstall fuse and test components (including connectors) of that circuit to find defective component(s)..." from 1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual;
Source: by Ford
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps it indicates a constant current drain which could cause a discharged battery. Possible sources of current drain are vehicle lamps (underhood, glove compartment, luggage compartment, etc.) that do not shut off properly.
If the drain is not caused by a vehicle lamp, remove the fuses from the interior fuse junction panel, one at a time, until the cause of the drain is located. If drain is still undetermined, remove fuses one at a time at the main fuse junction panel to find the problem circuit.
Electronic Drains Which Shut Off When the Battery Cable Is Disconnected
Repeat Steps 1 through 6 of the voltmeter drain testing.
Without starting engine, turn ignition on for a moment and then off. If applicable, wait one minute for the illuminated entry lamps to turn off.
Connect the voltmeter and read the voltage.
Test Conclusion
The current reading (current drain) should be less than 0.05 amps. If it exceeds 0.05 amps after a few minutes, and if this drain did not show in previous tests, the drain is most likely caused by a malfunctioning electronic component. As in previous tests, remove the fuses in interior fuse junction panel one at a time to locate the problem circuit. .."
Attachments
coolio2281
New member
you definately have what is called "Parasitic Draw" ....i suggest buying a cheap multi-meter (IF YOU DONT ALREADY HAVE ONE) and do some testing...first test....turn all electrical components off on the vehicle, let the vehicle set for a few moments and turn the headlights on for 1-2 minutes. (this gets rid of any static charge that is present on the electrical system.... once you let the headlights rid of the static charge, turn them off and disconnect the negative battery cable. turn the multi-meter to amp's. and connect the cable to the post with the meter and read the "Parastic Draw" i do believe but do not quote me on this, it shouldnt be anymore than .05A if so. open the fuse block and start checking the fuses to see which circuit is pulling the amp's...once you have found the correct circuit, that will help you pinpoint your problem. hope this helps...i do opollogize if iam a little off on certain area's if so i can look them up for you if they are not correct.
Thanks for the input guys. I had a chance to take a quick look at it today. With everything off; I'm reading 4 amps with a digital meter between negative post and negative cable! The fuel pump is not running with the key off. So I have a very excessive draw somewhere in the electrics if 1/2 amp is a normal reading.
I pulled the under-dash fuses one at a time, and it never really read much under 4 amps. Maybe I missed one but I'm pretty sure I tested all of them, definitely tested all the larger amp fuses. So I'm kinda at a loss right now... Do you guys think the ECC relay stuck closed could cause an issue like this? It will **** a brand new battery overnight!
I pulled the under-dash fuses one at a time, and it never really read much under 4 amps. Maybe I missed one but I'm pretty sure I tested all of them, definitely tested all the larger amp fuses. So I'm kinda at a loss right now... Do you guys think the ECC relay stuck closed could cause an issue like this? It will **** a brand new battery overnight!
coolio2281
New member
ok you definately have a draw on the electrical circuit, hmm, this is weird. you may have a short to ground on one of your circuit, my suggestion, get a wiring diagram of your vehicle and test the fuse block, make sure each circuit is operating at the specified range. anything more or less i would suggest running thro and checking for shorts. this isnt going to be easy. but will be rewarding when finished.!
yo,
do you have an under-hood lamp? if so, disconnect it, but be careful of assy since it is prob contains mercury
Under-Hood, Mercury Removal Guide, Bronco, Ford, 70-95, etc. Source: by wa.gov/pubs
Notice that they left out our Broncos in the Listing.. but incl BII & F-Series Truck (F 150-550) 1974-2000
here are more bulbs to ck
Bulb Chart w/Application in an 87
Source: by Mikey350 at SuperMotors.net
Here are bulb amperages listed in order of the chart by Mikey
161 0.19 AMP
194 0.27 AMP
1893 .33 AMP
T-3 AMPS (assumoong thsis is correct trade# for the 3 bulb)
161 .19 AMPS
1892 .12 AMPS
1156 2.1 AMPS
1157 2.1/.6 AMPS Park, Turn, Side marker lamps
912 1 AMP
2162 0.1 Amp
1445 0.135 Amp
2162 0.1 Amp
89 .58 Amp Instr Panel Courtesy
105 1.0 Amp
=============
disconnect all the alternator wires & see if the reading drops under 0.5A.; be careful
feel headlight switch panel area w/lights on; if it is very warm, inspect switch
Recall, Ignition Switch, Short Circuit Defect info for 88-92 Fords On April 25, 1996 Ford Motor Company announced the recall of approximately nine million cars, trucks and minivans that may be equipped with a faulty ignition switch that may be responsible for causing hundreds of fires. In no case has any death or serious injury resulted from these fires. The recall covers 1988-93 models sold in both the U.S. and Canada that Ford says, "In a very small number of vehicles, the ignition switch could cause an internal short circuit, creating the potential for overheating, smoke and possibly fire in the steering column of the vehicle." The faulty ignitions switches can cause a short circuit that may lead to a fire whether the vehicle is turned on or off.
altho year is off.... who knows if that sw version was installed in 87MY?
Someone here in da ZONE recently had a bad looking switch
--------------
any issues with ignition or bogging/shutting down after engine is warmed to norm op temp?
..if so:
TFI Module Failure, Troubleshooting Tips, Distributor-Mounted; "...1. Verify charging system operation; specifically, charging voltage. 2. Verify ignition system operation; specifically, there are no open or disconnected plug wires. 3. Remove distributor cap and inspect connections where TFI module hooks to the Hall Effect Switch connector. If there is any sign of deterioration at the connector, the Hall Effect pickup must be replaced. Crankcase vapors are forced into the distributor due to excessive crankcase pressure due to a worn engine or an improperly maintained PCV system. The crankcase vapors cause deterioration of the insulation around the connectors causing the module to short out..."
Source: by niehoff.com
do you have an under-hood lamp? if so, disconnect it, but be careful of assy since it is prob contains mercury
Under-Hood, Mercury Removal Guide, Bronco, Ford, 70-95, etc. Source: by wa.gov/pubs
Notice that they left out our Broncos in the Listing.. but incl BII & F-Series Truck (F 150-550) 1974-2000
here are more bulbs to ck
Bulb Chart w/Application in an 87
Source: by Mikey350 at SuperMotors.net
Here are bulb amperages listed in order of the chart by Mikey
161 0.19 AMP
194 0.27 AMP
1893 .33 AMP
T-3 AMPS (assumoong thsis is correct trade# for the 3 bulb)
161 .19 AMPS
1892 .12 AMPS
1156 2.1 AMPS
1157 2.1/.6 AMPS Park, Turn, Side marker lamps
912 1 AMP
2162 0.1 Amp
1445 0.135 Amp
2162 0.1 Amp
89 .58 Amp Instr Panel Courtesy
105 1.0 Amp
=============
disconnect all the alternator wires & see if the reading drops under 0.5A.; be careful
feel headlight switch panel area w/lights on; if it is very warm, inspect switch
Recall, Ignition Switch, Short Circuit Defect info for 88-92 Fords On April 25, 1996 Ford Motor Company announced the recall of approximately nine million cars, trucks and minivans that may be equipped with a faulty ignition switch that may be responsible for causing hundreds of fires. In no case has any death or serious injury resulted from these fires. The recall covers 1988-93 models sold in both the U.S. and Canada that Ford says, "In a very small number of vehicles, the ignition switch could cause an internal short circuit, creating the potential for overheating, smoke and possibly fire in the steering column of the vehicle." The faulty ignitions switches can cause a short circuit that may lead to a fire whether the vehicle is turned on or off.
altho year is off.... who knows if that sw version was installed in 87MY?
Someone here in da ZONE recently had a bad looking switch
--------------
any issues with ignition or bogging/shutting down after engine is warmed to norm op temp?
..if so:
TFI Module Failure, Troubleshooting Tips, Distributor-Mounted; "...1. Verify charging system operation; specifically, charging voltage. 2. Verify ignition system operation; specifically, there are no open or disconnected plug wires. 3. Remove distributor cap and inspect connections where TFI module hooks to the Hall Effect Switch connector. If there is any sign of deterioration at the connector, the Hall Effect pickup must be replaced. Crankcase vapors are forced into the distributor due to excessive crankcase pressure due to a worn engine or an improperly maintained PCV system. The crankcase vapors cause deterioration of the insulation around the connectors causing the module to short out..."
Source: by niehoff.com
I went through each interior fuse one by one and I was still reading a 4-amp draw with the ignition off. No lights seem to be on, and the fuel pump isn't running. Do you guys think a bad part in the alternator could cause such an excessive amperage draw? The old battery was strong before the vehicle starting draining suddenly. I have already replaced it with a new one so its not the battery at fault.
YO,
Diodes inside the alt could be leaky/shorted, thus causing drain, but the it could still put out between 13.0 & 15.0 volts w/engine idling & pass the Voltage Output Test, however it could not put out full current, & would fail the Current Load Test.
Remove & Charge Battery and take voltage reading (should be around 12.6 volts)
Disconnect alternator, then re-install battery for a day or so & then check batty voltage again; if no drain, then diodses are prob the issue.
or Take alt it to a parts store where they can BENCH-test it for free.
Diodes inside the alt could be leaky/shorted, thus causing drain, but the it could still put out between 13.0 & 15.0 volts w/engine idling & pass the Voltage Output Test, however it could not put out full current, & would fail the Current Load Test.
Remove & Charge Battery and take voltage reading (should be around 12.6 volts)
Disconnect alternator, then re-install battery for a day or so & then check batty voltage again; if no drain, then diodses are prob the issue.
or Take alt it to a parts store where they can BENCH-test it for free.
Last edited by a moderator:
It turned out to be a faulty alternator. I removed the wire harness from the alternator, and the amp draw while off dropped to zero. While running I was reading less voltage at the battery than when it was not running. I had it tested at the parts store and the guy said it was doing "weird things" on the load tester. It was so bad they couldn't get any good readings with a load applied to it. The diodes inside of it must have been toast. I replaced the alternator with a rebuilt one and it was reading a heathly 14.7v at the battery. Fingers crossed the battery doesn't go dead any more!
beast runner
New member
What I'm wondering is do you have an Electric Trailer Brake switch installed in your Bronco? I had the same problem with my 88 when I first bought it. A fresh 1000CCA battery would be toast in 3 days. I bought it from a landscaper who knows about as much about mechanical work as I do about building a rocket! I started working my way through things that I figured I don't need and won't use and I started with this trailer brake switch. That solved my problem! It's just a thought, maybe you could use a little of my experience here! Good luck
