Front heater pulling large amps...

[DomSmith]

73 FJ40 stock heater and switch...

The front heater seems to be pulling big amps (10+) when on high and low? A little less on low...

Where should I be looking for resistance? Swapped in a different switch with no change.

Didn't see anything in the FAQ's or by searching.

If I missed it, flame away...

Electroheads?

 

[Poser]

Just for the hell of it Dom, secure a ground wire from one of the mounting screws on the blower motor and run it to the negative side of the battery.

Post up the results.

 

[DomSmith]

Bolts have a good ground... no change. Still a big drop.

Checked the + side of the battery with a volt meter using each of the bolts as ground and they all passed.

 

[lrowe_csp]

Dom:
What did you finally figure out?

 

[FJforty]

Just my $.02, 10amps does not seem all that bad for a motor on 12 volts. Most older cars will dim the lights a bit if you kick the heater on, mine dim. I would guess 15 amps+ on a high setting.

 

[DSRTRDR]

why the heck do you need a heater in San Diego anyway

 

[amaurer]

Epic fail here so far - additional resistance in the system cannot possible explain high current draw. If 10 amps is too high (and as FJforty said, it might not be - thats only 120 watts, the same power a a big light bulb) then its cuz some of the motor winds have shorted.

Vad grounds/switches, etc, cannot explain this.

 

[Pin_Head]

its cuz some of the motor winds have shorted.

Bad grounds/switches, etc, cannot explain this.

So true.

V= I/R When I is high, R is low.

It is a short, not a bad connection or ground.

 

[FJforty]

V=I*R.

 

[mydogpea]

why the heck do you need a heater in San Diego anyway

 

[fj404life]

Just a thought...when I got my 69 the rear heater would barely spin.
Guessing it was drawing tons of power tring to spin that motor with its dry bushings.
Cleaned it up and oiled the shaft and spun it with a drill for a bit...and it spun up way way better and easier. I have been meaning to give my front blower motor the same treatment...seems to work ok though for now.

 

[Coolerman]

Just a thought...when I got my 69 the rear heater would barely spin.
Guessing it was drawing tons of power tring to spin that motor with its dry bushings.
Cleaned it up and oiled the shaft and spun it with a drill for a bit...and it spun up way way better and easier. I have been meaning to give my front blower motor the same treatment...seems to work ok though for now.

Ding! Ding! Ding!

When I first started working on my 71 front heater blower it was pulling 9.4 amps and barely spinning. After a complete tear down of cleaning, lubing and dressing the brushes and commutator, it now pulls 6.7 on high and 4.3 on low. (Measured with a Fluke 87)

My rear heater fan after cleaning now pulls 2.7 amps.

 

[FJforty]

Numbers, nice! They remove a level of speculation.

 

[einstein]

Also look at the electrical connector that is 3 prong where the fan connects. Mine was super dirty and that seemed to help tons by cleaning the contacts.


Matt

 

[DSRTRDR]

Numbers, nice! They remove a level of speculation.