Wipers and heater motor blowing fuse after running a minute or two.

[Jim S]

When I turn on either the wipers or heater (or both) the fuse will blow.  I replaced the fuse with a 30 amp breaker and that will trip after a minute or two.  The guages and shifter light are on the same circuit.  Is it because the motors are old and pulling too many amps? Any suggestions to keep them safely running?

Edited January 27 by Jim S
Mispelling

[mfg]

4 hours ago, Jim S said:

When I turn on either the wipers or heater (or both) the fuse will blow.  I replaced the fuse with a 30 amp breaker and that will trip after a minute or two.  The guages and shifter light are on the same circuit.  Is it because the motors are old and pulling too many amps? Any suggestions to keep them safely running?

I’d guess motors need lube.

[Jim S]

I forgot to mention, both motors run fine for a minute or so before the circuit trips.

[Gunslinger]

Did the problem begin at the same time with the two motors?  If so there might be some kind of cross-connection in the wiring creating an overheating issue requiring the circuit breakers or fuse to trip/blow.  

I would check all the ground connections as well as connections to the fuse box.  After so many years the connections could be corroded making for overheating of the wires.  

The motors themselves might need overhauled...maybe the wiring harness itself has become suspect and required replacing.  

[mfg]

By the way the motors will run a minute or two before the breaker trips is good… it indicates there is no ‘dead short’ in the wiring….

As I said previously, before you start throwing money & time at this problem..   lube the motors.

[ronmanfredi]

If it were me, I would first remove those components grounds and clean the terminals. Then remove the related harness plugs and clean the pins and sockets including the fuse box terminals.  This would remove the common resistance areas of the electrical system.  You can run an ohm meter from the negative side of the battery to the ground wire on each component to be sure the grounds are solid.  If your car has the bulkhead harness connector, then be sure to clean those terminals.

Now put a 10amp fuse in the fuse box and run the heater motor for several minutes.  If it does fine, then turn it off and run the wiper motor (with the wiper blade arms removed) at high speed for several minutes.  If in either case, the fuse blows, then the component needs repair/lube/replacing.  I also do a temperature check on the related harnesses by holding the harness at the component while it's running.  If the harness/wires are hot to the touch then you know you have a problem with resistance being caused by the component / wiring.                                              

[Jim S]

Thanks to all the contributors.  I'll dig in now!

 

[Jim S]

Problem solved! I discovered that the connections at the fuse panel were reversed at the wiper circuit breaker. The ignition hot wire that should go to the common input of the fuse panel was on the oposite side of the wiper circuit breaker.  Thus everything on the ignition circuit was going through the curcuit breaker before the common of the fuse panel.  Everything worked until the additional load of turning on the heater motor and/or wipers.  That additonal load would trip the breaker. All I had to do was reverse the connections and all is well. I guess I'm forever cursed with correcting previous owners mistakes!

 

[Gunslinger]

I've seen that more than once...having to undo what past owners have done before doing it correctly.