Hello,

My 88 F150 has a strange problem. It has a new battery and new alternator, both have been tested again to confirm they are good. The cables are good as well. When the truck is running with nothing electrical on it will charge at about 14.5 volts and I have no problems with it. However, when you turn on the a/c the truck will bleed off voltage. In about 5 minute it is down to only charging 13.0 volts and another 5 miutes it is close to 12.0 volts. After driving the truck for 30 minutes it is very difficult to start the truck because the battery is low. If the truck is driven without the a/c or the blower running the battery will recharge and there are not any problems. The problem seems to be the blower because with heat on instead of the a/c it will discharge the battery. So with that said I am leaning toward the blower or the relay mounted right beside it. Does this sound reasonable? I could be chasing my tail and it is something completly different causing the problem, but the blower seems to be a common thread in the problem. Does anyone have any other ideas? What should the resistance be on the blower and the relay? It is to hot this time of year to drive around without a/c. I have read that there is a diode in line of the alternator could this be bad? Any help is appreciated. Thanks

Having researched a little more I am wondering if it could be the starter. The startes sounds terrible and i had planned on replacing it soon. If it has a internal short that is causing current to drain off with the addition of the a/c running it could be more than the alternator can handle? Just a thought.

 

You live pretty close to me.

Next, I'm not wondering if the alt is still bad... it could be that it's getting too hot and producing less amperage then basically none. There's a diode pack on the alt itself, not inline. All that's inline is 6 wires to a fuseable link and one switched 12v.

Are you still running that lil 65-75A unit? If so, I'd consider duming that junk for a 130A 3G...

Only blower fan problem I had was the bearings in it took a dump. If the battery hardly has amperage that's why the starter can barely crank the truck. Stay away from AutoZone's cheapo reman parts, most are junk. I've had good luck with O'Reilly stuff.



PS - my Benz is sans A/C, I still drive it all the time during the middle of the day. You have to be hardcore.

 

The current alt has about 5 miles on it. It came from Oreillys and I made them test it before I took it. The old one I took up there was under warranty and was good but the gave me a new one anyway. It is a 75 amp reman unit. I threw my Powermaster 140 amp alt on there and the problem still exist.

I don't need a/c but to have a perfectly good one that I can't use is a beat down.

 

Check the wiring from the alt to the solenoid. Could be loose or corroded

 

Ok guys I needs more help! Thanks to Hit Man X for his help so far. I replaced the starter, solenoid, and inspected all the grounds. They all look good by the way. The starter needed to be replaced regardless of my problem. There is a relay? right next to the blower that has a bunch of coils on it and is part of the blower wiring, what is this part? I am really stuck at this point. Are there any tests that Oreilly or Autozone can do on the entire system? I consider myself to be a pretty good mechanic, and hate having someone else look at it, but I am lost at this point. Thanks again.

 

Have you checked to see if you have a slow drain anywhere? Do you have anything aftermarket in there? Maybe the volt reg is bad still?

 

Nothing aftermarket at this time except for the alarm. This is not a daily driven truck so I have not done a whole lot with it. I don't believe the alarm is the problem because I disconected it and nothing changed. I am thinking I may drive it to work all week and see if makes any difference being driven more.

 

Well I drove the truck on Sunday for most of the day. I had lots of things to do so it was a good opportunity to start the truck a number of times and run the air. Much to my surprise it made it thru the day fine, however I would periodically would check the voltage and it was lower each time I would check but it never really dropped below 13 volts. It almost seems like the reman alternator just can keep up with the power demands. I have heard that most reman units are about 5 to 10 amps less than what they say they are. The gauge on the dash seems to read about two volts lower that what my voltmeter hooked directly to the battery says.

 

Those dash gauges are all about useless. The speedo is decently accurate and the fuel level gives you an idea. The coolant, oil pressure, and volts are a laugh.

I installed all aftermarket for that reason to actually monitor what's going on under there.



Ooooo... have you checked voltage drop between the wiring from the alternator back to the solenoid? Perhaps the wiring is poor or something of that nature.

 

Ya, all the gauge are junk, but the reason I mention it is because there is a noticable difference in how the gauge reacts to accessories being used compared to before. I will check the wiring this weekend for a voltage drop. I have run thru just about everything at this point. As long as it will start and drive when I need it I may just say the heck with it.