Heater sapping power

[Jaime]

Hello,

Hope everybody had a happy new year.

I have a problem with my heater sapping power from my other systems. I seem to remember this being brought up before but I can’t find it. When I turn on the heater my volt meter goes from almost 14 volts to almost the first line after the 9 volt line. Then if my lights and heater are on and I turn on the wipers, they move very slowly. If I turn on my blinkers, then they blink very slowly. I can also see the needle jump when the blinkers are on. I also have a pair of Hella 500's on the truck. When I turn them on (thinking they would sap more power than the heater) the rest of the system works fine.

 

I have done cruiser's tips 1-5, then 27, and recently #28.

Any help is greatly appreciated. Thanks!

 

88, 4x4, open cooling system, upgraded head lights.

[Eagle]

The heater blower uses resistors to control the speed, and resistors create draw in the electrical system. It's also possible that your blower motor itself is getting tired and drawing more current than a new one would.

 

That said, I suspect that your alternator is dying. The parts chains like Auto Zone and Advance Auto can bench test it for you if you take it in. A regular shop can probably test it in the vehicle, but they'll charge. The chain stores will test it free, but you have to carry it in.

[Doc.]

I was thinking just what he said.

[Jaime]

Thank you for the response.

 

I forgot to mention that about a month ago I got a new battery from Auto Zone. The sales person went out with his meter/tool and tested the charging system. He said the only thing wrong was the battery. I think that I will take it in again and have it tested. If it tests good then I will have the alternator bench tested. If it is the alternator is it worth it to get a higher out put alternator or just keep with the stock one?

 

Also if it ends up being the blower motor how hard is it to remove, will I need to remove the dash, and how?

[mikekaz1]

blower motor is in your engine bay, on the passage side firewall, 3 bolts, normally rusty, 8mm I think

[Eagle]

Quick test -- the heater blower uses resistors to control the lower speeds, but there is no resistor on the high speed setting. Try running your heater on the high setting and watch the volt meter. See if it makes any difference.

[Jaime]

Yes it does. When fan speed is on high the volts drop more than when its on low.

[TheDude]

Have you replaced or upgraded your battery cables to a heavier gauge and added beefed up and extra grounds?

Just doing heat made an amazing difference with how everything on electrical system works.

[Jaime]

So if I need to replace the motor I can do it thru the engine bay. That works for me.

 

I have added the extra ground to the battery but I have not upgraded to a heavier gauge cable. Do you have a part number and store I can purchase them or what gauge wire should I look for.

[mikekaz1]

Napa has a whole shelf of battery cables

[cruiser54]

So if I need to replace the motor I can do it thru the engine bay. That works for me.

 

I have added the extra ground to the battery but I have not upgraded to a heavier gauge cable. Do you have a part number and store I can purchase them or what gauge wire should I look for.

20 minute job. 

[Gene]

Hi Jaime,

 

Do you have a volt meter? You can probably buy one for about $10, please get one of these, and don't be afraid to use it.

 

Try to find out where the voltage is dropping. For example, check voltage right at the battery posts. Then, check at the battery terminals. If there is much difference between these readings, it would indicate corrosion where the battery terminal meets the post.

 

Then move the negative probe to the engine block, and to the firewall, finally as close to the fan housing as you can get.. If there is a significant difference here, that would indicate a problem with one of the grounds.

 

But if  that's not the case, then move the negative probe back to the battery, and start moving the positive to different locations.

 

Systematically checking this should give you an idea where the voltage is dropping, and then hopefully you'll be able to clean/repair the offending connector.

 

Have the heater blower running full speed while you're doing these tests.

 

Good luck!

 

Gene

[Jaime]

Hello,

Well this weekend I replaced the ground cables with a thicker gauge cables. I probed the system and could not find any change in voltage as I probed. I went ahead and replaced the blower motor. None of this made any difference. It still saps power when the heater is on. I did attempt to replace the resistor on the inside of the cab but was unable to. Autozone gave me one with a metal guard that would not let it sit right in the slot. So I will have to take it back and see if maybe NAPA has the correct one.

Now on the connector to the resistor it looks like it is a little melted. I also think that maybe Eagle was right and I need to replace the alternator. But I had it tested twice and was told that it test good under load. What do you guys think?

[Eagle]

If the votage drop still happens with the blower on high speed, the resistor pack isn't causing it because there is no resistor in the circuit on high speed. I would pull your blower motor and check it out physically. When you get it out, there's a round "squirrel cage" blower impeller on the end that goes into the air box. Try spinning it by hand. It should spin freely, with no resistance (or almost no resistance). What you've got is a mechanical device with a metal shaft that rotates in two metal bushings (not bearings) that haven't been lubricated in25 years. It may be running dry at this point, and metal on metal doesn't work very well.

 

It may be possible to dribbly some lightweight oil into the end with the impeller on it. The other end is sealed, but people have carefully drilled a small hole in the little bump where the end of the shaft is located so they can get a few drops of oil in there. Then cover the hole with tape or mastic or RTV. Just don't use too much oil, because you don't want it to seep into the electrical contacts inside.

[Doc.]

But he said he replaced the blower motor (and it made no difference).

[Jaime]

So if it's not the resistor what else can it be?

[Gene]

Hi Jaime,

 

Two basic possibilities:

 

1. The system voltage is low. This would involve weak battery or weak alternator. To test this, measure voltage AT THE BATTERY POSTS when the fan motor is running. If you have low voltage at the battery posts, you have a weak battery or alternator (probably both.) I think that this is very unlikely.

 

2. If you have 13.5 volts or so at the battery posts when the fan is running, then you are losing voltage between the battery and the fan.

 

Please post voltage at battery posts with fan running.

 

Thanks.

 

Gene

[Jaime]

Hello,

 

So I put the volt meter on the battery posts and I got these results with the engine running:

nothing on 14.3 volts

lights only 14.1

fan on low 14.1

fan on medium low 14.0

fan on medium high 13.9

fan on high 13.8

with the fan on high, lights on, blinkers on, and wipers on 13.7 - 13.8.

 

What do you think?

 

Jaime

[cruiser54]

I think you're fine. Ever see this?

 

http://www.jeepforum.com/forum/f11/renix-voltage-gauge-fix-684375/

[Jaime]

But it doesn't explain why the blinkers and the wipers run very slow when the blower is on high.

 

Also I don't have AC but it acts like a vehicle with AC when it is turned on. The engine bogs down. 

[cruiser54]

Voltage is good and amps are low. Voltage is getting bottled up somewhere or the alternator is putting out low amperage. . 

[Gene]

Hi Jaime,

 

First, we feel your pain. Things like these can be very very frustrating and time-consuming to track down.

 

Think of electricity like water. In your house, you have a water main coming in. Then you have different pipes, leading to various faucets.

 

If you have low water pressure at one faucet, it may be from low water pressure coming into the house, it may be a problem with the large distribution pipe in your house, or it may be a problem with smaller branch lines.

 

Electricity is the same. You have already checked the "water main". The voltage that you read that the battery is fine. This is not a problem with your battery or alternator. You were checking these voltages with the engine idling, so the alternator was only putting out a small fraction of its total output.

 

The "pipe" that goes to the heater motor, as well as the other accessories (linkers and wipers) that seem slow, has the problem. The "pipe" that you put in for your Hellas does not have a problem. Again, this is further evidence that the battery and alternator are not the problem.

 

So you have to troubleshoot, step-by-step, to see where the voltage is being lost.

 

I don't have access to a wiring diagram right now. If someone could post a link to home wiring diagram, we could go through that. However, generally speaking, the wire probably goes from the battery positive to the relay on the fender well, to the 101 connector, to the inside fuse block, to the ignition switch, to the heater switch, heater resistor, and heater blower motor.

 

Since blinkers and wipers are affected, I doubt that it's just the heater switch or resistor circuit. I believe you said you replaced the 101 connector completely. I suspect it's somewhere related to the inside fuse panel or the ignition switch. In other words, where the "pipe" supplies the blinkers, wipers, and heater blower is where the problem exists.

 

Again, a specific wiring diagram would be very helpful.

 

Good luck!

 

Gene

[Gene]

Ironically, another thread posted a link to wiring diagram.

 

Here's the flow of power:

 

Battery uses a red wire to go to the starter relay.

 

Green fusible link goes to connector D4, then red wire to ignition switch pin 3.

 

From ignition switch, there is a brown wire, which goes to a junction point, then runs to the inside fuse box, 25 amp fuse for the blower.

 

There's then a violet/yellow wire that goes over to the heater switch.

 

 

 

So, in all likelihood, somewhere between the starter relay and the blower switch is the problem.

 

Easiest point to check the voltage would be at the 25 amp fuse itself, with the engine running and blower on, check the voltage at this point. The plastic fuse actually has little cutouts where the metal tab is exposed, you can just put the tip of the voltmeter probe on this. Voltage will probably be low.

 

Then your troubleshooting is between the starter relay and the ignition switch and the inside fuse panel.

 

 

 

Just to be sure, you did bypass the large connector on the engine side of the firewall, connector 101, per Cruisers tips? This would be most likely place for the problem.

 

Gene

[cruiser54]

Gene, you are on to something. The brown wire at the ignition switch feeds blower motor and turn signals as well as something else. The switch overheats and burns the brown  wire at the connector per the photo below.

 

[Jaime]

Hello,

 

Thanks for the great response. You have definitely given me a solid starting point. I plan on tackling the system this weekend.

 

I wish I could do it tonight but it's dark and cold out. There is only two of us in our department and my partner is out for the next few weeks. So that means a lot of 12 to 14 hour shifts.

 

Thanks again for all the great info.

 

Jaime