Cab heater electric draw

[Lax]

Okay. Here is one for you. I just got my cab heater hooked up and took a couple hour drive today. I visited Mangus580 and had a nice time but to short. Anyway I decided to run my cab heater on hi to see how it worked. Seemed to work okay but I noticed that it seemed to draw a lot of electricity. In fact the needle on the amp meter was well into the yellow. That is strange because it normally is right dead center in the green. In total I was running the heater, headlights (one bulb is now dead on low beam) and just the regular accessories. Nothing to much. I thought. When I got about 30 minutes from home on my way back I turned off the heater and all lights as an experiment to see what would happen. The needle started to climb back up towards the green again before I shut her done afterthe last 30 minutes of my trip.

My question is should I always expect that much draw from the heater? When I have run just the lights as I should the needle was perfectly in the green before I hooked up the heater. Any advice? Thanks.

 

[rmgill]

I'd check grounds to be sure they're all good then check connections. I dont' have this issue with my truck. The blower grounds through the chassis, so make sure it's got a good metal to metal contact with the fender.

 

[jwaller]

The gen should be able to crank out more amperage than the all the stock accessories on the truck. as ryan said you have a problem with a ground or failing generator.

 

[doghead]

My heater is supplied through the circuit breaker on the firewall. When I first got the truck the blower motor would not run and would trip the breaker. After a little testing, I determined that the blower motor was bad. I replaced it with a used one and have had no trouble since. I don't remember the blower motors amp draw but, it is not much.

 

[Lax]

Thanks guys. I thought it was really strange that a little blower motor would draw that much power. How would I check the ground??? I'm clueless on where and how.

 

[doghead]

The blower motor is mounted to the heater/plate attached to the fender (clean a good ground at a bolt or two). The next place to check and clean would be the ground wire under the drivers side headlight/Bo light (it goes between the frame and the headlight panel). Btw, your headlight is grounded here also or may be near this. You could also just hook up a temporary ground wire from the blower motor-case to a good ground to see if you have a problem with the blower ground. Where did you connect to the harness for the supply power for your blower switch? If you have a bad ground on the blower it should not create a large draw on the batteries. A short to ground (possibly internal in the blower motor) will cause a large amp draw.

 

[houdel]

Is your truck running OK with the normal accessories (lights, etc.) operative? If so there might be a problem with the heater blower itself. If the problem only occurs when you are using the heater, I'd expect a problem in the blower motor. I haven't checked mine, but I'd suspect it only draws a couple of amps. Check it with a DMM, if it drawing more than 2-3 amps the problem is most likely a ground short. Check the current draw from your alternator with the normal accessories (lights, etc.) working. Then check the current draw with the blower motor running. If there is a significant difference with the blower operating, the problem is the blower. If there is a minor difference with the blower operating, chances are the alternator is not functioning properly.

 

[Lax]

The problem seems to be when I use the blower moter. I had a guy that has installed the heaters before do the instilation for me last month. He had parts I needed to have the heater complete and he seemed to know what he was doing. Last week was the first time I used it for more then 20 minutes.

I do know that I have never had any problems with the amp meter not staying right in the middle of the green before. Now with the heater working the amp meter drops to the middle of the yellow. I also noticed that my passenger side low beam headlight is not working too. Are these related? Do you think I should just pull the blower motor and get a new one? I agree with you guys. A little blower motor should NOT be pulling that many amps on a 24 volt system. What do you guys think? Where can I get a blower moter and how much should I expect to pay? Thanks.

 

[jwaller]

does the pass side headlight not work all the time or only when the blower is on?

 

[Lax]

Good question. I'll have to check that. I have to think they are not related because it is only the LOW beam that does not work. The HIGH seems to work fine. I'm guessing it must be just the bulb. Yes? No? Any thoughts?

 

[houdel]

Of course, it just could be the passenger low beam filament is burned out. Or, it could be your installer really screwed up some wiring when he installed the wiring. Test #1 is to put a DMM on the blower lead and see what it is drawing, should only be a few amps. You could have a bad blower motor, but I can't imagine one drawing that much current without quickly burning itself up. Other than that, dig out a wiring diagram, follow the blower and low beam circuits back to a starting point and start checking current draw until you find the circuit sucking up all your current!

 

[BFR]

FWIW the data plate on the one soon to be installed in my truck says "6.5 amps"

 

[houdel]

Joel - 6.5 amps is a lot of power, by a factor of about 2x what I would have expected. I didn't notice an amperage rating on any of my heater data plates. Now 6.5 amps is some 10%+ of the (60 amp) alternator output, but I have no problems at all running my heater. Either LAX has a 30 amp alternator, or something else is sucking off the juice!