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Kohler 6.5 controller A-245701, need charging help

Kenny Crenshaw

Registered
My generator seemed to be putting out too many volts charging the battery. It was putting out about 10 amps @ about 16 volts. Someone suggested that I take apart the charge control relay, the Prestolite TCA 4004. So I did. The contacts looked old and pitted, so I ran some sandpaper through the, 1000 grit, until they looked better. They looked to me to be made of bronze. I put it back together, and kind of figuring what the relay did, it seemed to switch the charging system from one path to another. It seems that when the relay is activated the charge rate decreases, I think based on which resistor is passed through. So, I figured out what terminal to put a jumper wire on, and made a path to the positive terminal of the battery. Without the jumper hooked up, the battery was being charged at 17 volts and 4.89 amps. With the jumper hooked up (activating the relay, which breaks the connection) the volts drop to 16 and the amps drop to .60. At one time when I activated the solenoid the volts dropped to 14.

It seems that whatever system is supposed to activate that solenoid is not working. What and how do I test moving forward? Can someone tell me what the other two relays do?
 

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Kevin K

Subscriber
Last Subscription Date
07/12/2019
The TCA4004 is a voltage sensitive relay commonly used as part of a two step battery charging system in older revolving armature generators in which the battery charging current is taken from the exciter, which is typically 17 to 30VDC depending on the model. The relay is used along with two high power resistors. The TCA4004 has a set of normally closed contacts. When the generator is first started and the battery voltage is low, the contacts are closed putting the two resistors in parallel resulting in a lower combined resistance and therefore higher battery charging current. When the battery voltage reaches approximately 14 VDC, the relay pulls in opening the contacts and disconnecting one of the resistors from the charging path. The result is a higher resistance and lower charging current.

You can test the TCA4004 with a variable power supply. With the cover on the relay, slowly increase the voltage across the relay coil until the relay pulls in. The voltage should be approximately 14 VDC. I believe the pull in voltage can be adjusted but it must be checked with the cover on.

You can obtain a wiring diagram of your generator by contacting a Kohler distributor as described in posts 6 & 7 of the Kohler FAQ at the top to the Kohler forum page.

The other two relays in your controller are most likely a Cranking Control Relay (CC) which disconnects cranking current when the engine starts, and CR, the Crank/Run relay, energized when the generator is cranking or running. You need a wiring diagram to be sure.
 

Kevin K

Subscriber
Last Subscription Date
07/12/2019
Building a bench variable power supply is easy and cheap. Google "How to build a variable bench power supply" for lots of ideas. To check this relay you need something that can be varied between say 5V and 20V. It does not need much current capability.

On the other hand, Chinese built lab power supplies are quite cheap. Search Ebay or Amazon for: "adjustable power supply".
 

LWB250

Registered
Do also consider that these systems were intended to charge multiple battery systems, often series/parallel depending on the cranking voltage. The old lead acid batteries were far more robust that batteries of today, and as a result could handle being overcharged somewhat.

Good luck!

Dan
 
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