Help! 1994 Ranger dies when I run heat and lights!?!

[Art]

I love my 1994 Ranger. That being said I'm having a bit of trouble with it and thought I'd see what the forums thought. Last week I started having a peculiar problem. Whenever I run my heat and my headlights at the same time there is a significant drain on the battery, which is apparent on the voltage gauge, and also can be identified by a dimming of the headlights, dash lights, and accessories (led floor lights, radio, etc.). I can drive it around running my heat with no issues, and I can also drive it with the lights on without any problems, but when I run them together, I'm losing a ton of voltage. So much in fact, that my turn signals wont even blink. When this is occurring, and I have minimal voltage, simple things like hitting the brakes show even more drain on the battery, pushing the volt gauge nearly into the red zone. same with the turn signals, and my power steering feels stiff. Revving the engine pulls even more power, opposed to giving more juice! There is usually a squealing sound that accompanies this, although the condition still happens without the squealing noise sometimes. The battery tests good, and so does the alternator, although my testers maybe not the best. the alternator is pumping a little bit high, and one of the connectors at the alternator the plastic clip has broken. I have ruled out the connection because when I kill the lights and heat at idle the battery goes right back into the normal zone. Indicative that the alternator is pumping. If I shut the truck off while there is drain on the battery I have to jump it to get it running again. If i run the heat at full blast and turn my brights on, It sucks so much juice that I start losing my gauges. My temperature gauge has been acting weird recently also, it goes up to the top end of normal then drops back down real quickly. Don't know if that may be related or not. Tonight on my way home from work it was 4 degrees F and I decided to heck with it and ran my heat and my lights. when I turned on the turn signal and hit my brakes to make a turn with the heat and headlights on, it was too much and she died. Me and my coworker pushed it the couple hundred yards to his place. we jumped it, and i drove it home without the heat on and just the lights with minimal problems. What in the world is going on with my truck? Any and all help will be greatly appreciated. Thanks, Art.

 

[6.2]

My guess is a bad alternator. When the truck is running, it's the alternator that provides power to things that require power.

 

[DRanger024]

Test the alternator output under load. With the headlights and heater on. Grab a buddy if the truck won't stay running. My dakota has a 90 amp alternator in it due to the severe lack of electronics in it ('95 2wd with manual trans, windows, locks etc). The electric cooling fan I installed draws enough current to almost do the same thing when it kicks on with the headlights on and the heat running full blast. It has the original alternator in it to boot so I'm thinking its a little weak anyways. It will be replaced with a 120 amp unit.

 

[RonD]

An alternator has 3 "fields"(phases) of AC power, this is converted to DC in the alternator, over time 1 or 2 of these "fields" can fail, so alternator produces less amperage, same DC voltage just less power.

Your description would fit failed "fields".

Engine off, key off - battery should read 12.6vDC or more volts, 12.4vDC or less means it is time to replace battery.

Engine running with all accessories off - battery should read 13.8vDC or more
Engine running with all accessories on - battery should read 13.8vDC or more
This is at idle, if you increase RPM voltage should be above 14vDC but never above 14.8vDC

Voltage will drop as each accessories is turned on, but voltage regulator should respond by adding more power, so it should return to approx. 14vDC.
If it doesn't then either the regulator is not working or 1 or 2 of the 3 "fields" are not working.
The voltage at the alternator would only drop when the amperage it can produce has been exceeded, so you need to do this load test to see if alternator is fully working.

An alternator with all "fields" working can supply all the power needed for factory equipment, when you add "extras" then you might want to get a higher amperage alternator.

These electrical diagrams for charging systems are pretty standard for most vehicles.
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

An alternator sends power to the electrical system on a few different wires, if any of these wires are corroded it can restrict the maximum amperage available or prevent the regulator from adding more amperage.


As far as the temp gauge, do you notice the heater in the truck gets colder as temp gauge goes up, if so you might have an air bubble in the system.
If heat in truck doesn't change colder or hotter when temp gauge goes up then sending unit may be going bad.
If heat in truck gets hotter with temp gauge going up then t-stat may be sticking.

And finally if heater in truck has been producing less heat than normal, over the last few months, then you probably have a partially blocked heater core.
Good news is that it is easy and cheap to replace, 4 screws and $25.
If you don't see a heater control valve near the firewall in the engine compartment then the heater core is being used as part of the cooling system, a by-pass for the water pump, not a great idea but they did this on some models, so if the heater core starts to get blocked up the temp gauge will go up and down.
My '94 4.0l was setup like this, replaced core and all was well with engine temp and temp gauge.

 

[JC 97]

Check your grounds.My '97 did the same thing.I cleaned the grounds and added one.It cleared my problem.By all means check your charging system too.

 

[cammeddrz]

check for AC current at the battery posts while running.
if a diode inside the rectifier circuit of the alternator has failed it can also bleed AC current into the DC system which "cancels out" a certain amount of DC voltage, anything less than .4v is ok

but either way the problem seems to be in the alternator.

 

[adsm08]

So Cam deigns to post again. I thought you were chillin with Chance.

check for AC current at the battery posts while running.
if a diode inside the rectifier circuit of the alternator has failed it can also bleed AC current into the DC system which "cancels out" a certain amount of DC voltage, anything less than .4v is ok

but either way the problem seems to be in the alternator.

I usually like to see less than .03V A/C. By the time I see tenths of a volt I put a new alternator in.

 

[cammeddrz]

So Cam deigns to post again. I thought you were chillin with Chance.

who is chance?

 

[adsm08]

Chance is dead.

 

[Redneckryder]

Stupid question....Have you checked to make sure the belt is tight?? low power, heating up....sounds like the serp belt is slipping. Check the tensioner or something? Just throwing it our there....

 

[BRUTUS_T_HOG]

Sounds like a loose belt or shorted battery to me. Could be the alternator of course, but the battery is supposed to do the hard work and the alternator is meant to maintain the battery

How old is the battery? Have you had it tested on a load tester rather than a voltmeter?

 

[PanamaExpat]

Sounds like a bad diode in the alternator to me also. Go grab a new one or get a higher amperage one from the JY. I personally prefer to rebuild my own alternators and starters as I know they are right when I am done but most people most people seem to be afraid of doing that so they grab AutoZone crap replacements.

 

[Andy D]

P Ex , Right now, both my starter and alternator are doing OK , but you are right, and I will be posting up a storm should the occasion arise. I am in a perfect position to overhaul one, because I dont depend on the Rat. I was practically raised in an old school garage and machine shop. I remember Sonny, cleaning up commutators on the lathe that was powered by an open overhead leather belt. I have had some success rebuilding electrics. In the past, though it was dead daily driver and I needed it to run the next morning. That is when buying a re-built happens. I will eat the core charge before I let go of the original unit, in case it works better than the one I just bought.