Ignition Problem with Unilite System
Thread Starter
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Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Ignition Problem with Unilite System
My '67 240 has a Unilite ignition in place of the old points. My problem is that when I turn on the heater motor, the engine dies. Dead. No spark. Later it comes back to life. I disconnected the heater blower motor and checked it on a battery charger for current draw. It pulls about 5 amps, seems okay as compared to a spare I have, and runs fine.
I am wondering: Might the dropping resistor still be in the primary circuit? Should there be one with a Unilite module? It seems like the heater motor current draw might be pulling down the voltage to the module to where the protection circuits cause it to drop out for low voltage.
Is the proper wiring for this application to have the module directly off IGN on the switch and the heater motor off ACC?
Thanks, guys. I am baffled by this. I am thinking of putting a relay on the heater blower to take the current out of the ignition switch. Any opinions or advice is much appreciated.
I am wondering: Might the dropping resistor still be in the primary circuit? Should there be one with a Unilite module? It seems like the heater motor current draw might be pulling down the voltage to the module to where the protection circuits cause it to drop out for low voltage.
Is the proper wiring for this application to have the module directly off IGN on the switch and the heater motor off ACC?
Thanks, guys. I am baffled by this. I am thinking of putting a relay on the heater blower to take the current out of the ignition switch. Any opinions or advice is much appreciated.
Laughing Gas
Joined: Jul 1999
Posts: 1,048
Likes: 22
From: Lacey, WA
Ignition Problem with Unilite System
John,
Does this condition occur when you turn on any other high current items? Like your head lights? High beam? The reason I ask is it may be possible that your voltage regulator may not be regulating when under a heavy load thus causing this condition. Just a thought. Good luck.
Lee
Does this condition occur when you turn on any other high current items? Like your head lights? High beam? The reason I ask is it may be possible that your voltage regulator may not be regulating when under a heavy load thus causing this condition. Just a thought. Good luck.
Lee
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Ignition Problem with Unilite System
John, the Unilite must have a ballast resistor or a resistor wire like the stock one in your truck. The resistor wire comes directly out of the ignition switch, it is usually pink if it hasn’t been overheated. There should be nothing else connected to this wire except the ignition. I’ve been running a Unilite on my ’68 for over 10 years now and it has never skipped a beat. I can check some wiring diagrams later this evening to see where the blower motor taps into the electrical system.
Barry
Barry
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Ignition Problem with Unilite System
John, I looked at the wiring diagram and yes the blower motor power comes off the ACC on the switch while the ignition comes off the IGN. 5 amps seems fine for the blower motor current draw. If the blower IS pulling down the voltage, you could measure it on the coil + terminal while turning on and off the blower. This is baffling, could the contacts in the ignition switch be worn out? Maybe try replacing the ignition switch first before going the relay route.
Barry
Barry
Thread Starter
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Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
Ignition Problem with Unilite System
The problem does not happen with headlights on. Only the heater motor. I did replace the switch and the problem persisted. There is a ballast resistor in the circuit.
The truck is obviously miswired. Besides the heater motor on IGN, I see some high gauge, thin wires running out off the ignition switch. I am going to get the heater motor off IGN to ACC, and put in some heavy 10 gauge wires out to the coil along with a new resistor.
I suspect that the internal terminals on ignition switches are smaller on IGN than ACC. Maybe there is too much heat at the contact from the blower motor pull causing it to expand, break contact, and then heal when it cools. The message here seems to be: Make sure all accessories pull off the ACC post where they belong, not on IGN.
Thanks, guys. I very much appreciate the talent and comradeship on this web site.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Ignition Problem with Unilite System
I believe the high gauge thin wire you see coming out of the switch is the resistance wire. It is fatter than the other wires coming out, should be pink in color. The thin wires inside the insulation have a silvery color and are very flexible. This is the ballast, there shouldn’t be an additional ballast resistor. The total resistance of the wire is between 1.3 and 1.4 ohms. Hope this helps.
