Electrical gremlins

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bobmc

Member
I am working on a new to me 31 s/w sedan. When the car was purchased the amp meter did not work at all. No movement of any kind. While I was rewiring the gen to terminal box I also picked up the starter mounting bracket and disconnect switch. Installed the switch on the bottom starter bolt and installed the switch on the bracket. Used a new battery cable that ran from the pos (ground) post of the battery to the switch. Installed a new cable from the other post on the switch to the frame completing the ground circuit. also installed a new amp meter in the dash. get in the car and the new meter is reading -10. Start the car and increase the idle and the needle moves to 0. Using my multi meter and checking both sides of the new amp meter I have a reading of 7.4 volts both side. Now I removed the cable from the pos neg side of the battery and reinstalled the original braded steel cable that went from the cross member to the battery post everything works like it should. Amp meter is at 0 with everything off and touching the brake or blowing the horn the meter moves to the negative side. Start the car and increase the idle the meter moves to +10.
Any ideas as to why this happens. everything from the battery through the switch is on the ground side. nothing to short out?
 
If I read your post correctly, your ammeter read backwards when you connected the negative battery terminal to ground, which is wrong. Then you switched the battery around and grounded the positive terminal, which is correct, and now your ammeter is happy. Right?? Model A's are positive ground. You solved your own problem.
 
The +10 amps may be correct. It depends on where the 3rd brush is set in the generator. If set to charge 10 amps it will charge at that rate as long as the engine is running. At least above idle. There is NO current regulation in the standard/unmodified Model A charging system. Consequently you must maintain the proper level electrolyte in the battery.
Many have purchased and installed a FUN PRODUCTS voltage regulator available from a regular poster on this forum.
 
With out the cutout switch it seems as though everything is as it should be except for the charge rate. Thats high and can/should be able to be adjusted thru the third movable brush.

It seems as though there is something wrong with the way the cutout[ shut off switch] is installed.
 
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Sorry, my mind goes faster than my fingers can type, and I am old. The positive post of the battery has always been connected to the ground. The only change was the installation of the disconnect switch. Originally the braided steel ground strap went from the pos post of the battery to the cross member. With the installation of the disconnect switch I installed a new cable from the pos post of the battery to the switch. The other post of the switch was grounded to the frame. All Clean metal and new bolts.

With the switch in the circuit the amp meter read -10 and with increase in engine speed moved to 0. remove the switch an install the ground from bat to cross member the amp gauge works as it should.

sorry for any confusion
 
bobmc said:
Sorry, my mind goes faster than my fingers can type, and I am old. The positive post of the battery has always been connected to the ground. The only change was the installation of the disconnect switch. Originally the braided steel ground strap went from the pos post of the battery to the cross member. With the installation of the disconnect switch I installed a new cable from the pos post of the battery to the switch. The other post of the switch was grounded to the frame. All Clean metal and new bolts.

With the switch in the circuit the amp meter read -10 and with increase in engine speed moved to 0. remove the switch an install the ground from bat to cross member the amp gauge works as it should.

sorry for any confusion
Click to expand...




I thought I read the post correctly, In that the system seems fine [ except for the high charge rate] without the switch being installed.

It appears to me that there is something wrong with the way the switch is wired or installed, or, that the switch may be defective. There should not be a 10 amp draw from the switch.
 
If the ammeter is by chance still installed backwards then the 10 amps of "discharge" might really be 10 amps of charge, which would be indicative of a bad wire or some other high resistance bad connection somewhere in the charging circuit. If that is the case, the generator sees low voltage due to the resistance and tries to really up its charging rate to its capacity.

Just another thought to add to other opinions.
 
Vehicle as Ford built it,
-Pos battery to ground/crossmember.
-Neg battery to starter switch
-Ammeter reads zero
-Turn on lights ammeter discharges [ key/engine off]
-Engine running fast idle ammeter charges

Vehicle with electric disconnect switch on starter,
-Neg battery still connected to starter switch
-Pos battery now to one disconnect terminal and second lead from second terminal to ground
-Ammeter reads -10 engine/key off, 0 with engine running

Am I understanding this correctly ? What does ammeter read when lights turned on with disconnect ?

We'll work on the high charge rate when first problem is corrected. [ third brush adjustment]
 
Just for clarification, which switch was purchased? There are some that probably shouldn't be used.
 
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