The 3aw relay in my series 1.5 '68 etype has failed. I have no ignition light, poor charging and poor voltage to gauges. Will replacing 3aw fix all or are there other issues I should consider?
Tom
3aw relay
#2 Re: 3aw relay
Tom,
I believe the 3AW is simply involved with switching the ignition warning light on and off. When there is no output from the alternator's AL terminal, the 3AW's WL terminal is essentially connected to ground. The ignition warning bulb is connected to the WL terminal (ie ground). When the ignition switch is turned on, 12v is applied to the other side of the bulb and the bulb illuminates.
Once the alternator is generating output, there should be an AC voltage at the AL terminal, which is connected to the 3AW AL terminal. It should be about 7-8 volts as the AL terminal is only connected to one of the spurs of the rectifying bridge. This AC voltage breaks the path to ground from the WL terminal and the bulb will go out.
I suspect the poor charging is either the 4TR unit or alternator. First test the 4TR unit - it's very straight forward and covered in the service manual. You just remove the connector and replace with a single jumper lead. If that is ok, then check the alternator.
If you have a multimeter, check whether the alternator is producing an output on the AL terminal (don't forget to put meter into AC mode). If it's not then it's likely to be failed diodes in the alternator.
Chris
I believe the 3AW is simply involved with switching the ignition warning light on and off. When there is no output from the alternator's AL terminal, the 3AW's WL terminal is essentially connected to ground. The ignition warning bulb is connected to the WL terminal (ie ground). When the ignition switch is turned on, 12v is applied to the other side of the bulb and the bulb illuminates.
Once the alternator is generating output, there should be an AC voltage at the AL terminal, which is connected to the 3AW AL terminal. It should be about 7-8 volts as the AL terminal is only connected to one of the spurs of the rectifying bridge. This AC voltage breaks the path to ground from the WL terminal and the bulb will go out.
I suspect the poor charging is either the 4TR unit or alternator. First test the 4TR unit - it's very straight forward and covered in the service manual. You just remove the connector and replace with a single jumper lead. If that is ok, then check the alternator.
If you have a multimeter, check whether the alternator is producing an output on the AL terminal (don't forget to put meter into AC mode). If it's not then it's likely to be failed diodes in the alternator.
Chris
| Link: | |
| BBcode: | |
| HTML: | |
| Hide post links |
#3 Re: 3aw relay
Great advice from Chris- that is the best path forward for troubleshooting your issue. If you do discover that the 3AW is not up to snuff I would seriously consider replacing it with an electronic version from SNGB or CoolCat. More $$(££?) but no worries. Never (well, almost never) fail again!
Doug
1968 Series 1.5 E-Type OTS (Early production)
1968 Series 1.5 E-Type OTS (Early production)
| Link: | |
| BBcode: | |
| HTML: | |
| Hide post links |
#4 Re: 3aw relay
Thanks Chris and Doug. I am going to have the alternator and 4TR bench tested.
Doug, are you familiar with this document--great read and good info:
"JCNA Model Year ‘68 E-type Judges’ Guide
The only true Series 1.5 E-types
For Cars Imported to the North American Market"
Tom
Doug, are you familiar with this document--great read and good info:
"JCNA Model Year ‘68 E-type Judges’ Guide
The only true Series 1.5 E-types
For Cars Imported to the North American Market"
Tom
| Link: | |
| BBcode: | |
| HTML: | |
| Hide post links |
#5 Re: 3aw relay
Tom:
I do have the '68 Judges guide and refer to it often. I do take issue with a couple of items in it and have even had discussions with George Camp about it. The JCNA position is if it's in the guide it is 100% correct for all Series 1.5 cars. So if you are going for Concourse wins follow the guide to the "T". I have discovered that there isn't a correct wiring diagram for the true Series 1.5 cars. Every one I've found shows a starter relay and neither my early production 1.5 or another lister's late 1.5 ever had one. It was added at some point for the Series 2 cars. May not be a bad idea to add one to reduce the current draw through the ignition switch. Anyway, good luck troubleshooting your electrical issues!
"JCNA Model Year ‘68 E-type Judges’ Guide
The only true Series 1.5 E-types
For Cars Imported to the North American Market"
Tom[/quote]
I do have the '68 Judges guide and refer to it often. I do take issue with a couple of items in it and have even had discussions with George Camp about it. The JCNA position is if it's in the guide it is 100% correct for all Series 1.5 cars. So if you are going for Concourse wins follow the guide to the "T". I have discovered that there isn't a correct wiring diagram for the true Series 1.5 cars. Every one I've found shows a starter relay and neither my early production 1.5 or another lister's late 1.5 ever had one. It was added at some point for the Series 2 cars. May not be a bad idea to add one to reduce the current draw through the ignition switch. Anyway, good luck troubleshooting your electrical issues!
"JCNA Model Year ‘68 E-type Judges’ Guide
The only true Series 1.5 E-types
For Cars Imported to the North American Market"
Tom[/quote]
Doug
1968 Series 1.5 E-Type OTS (Early production)
1968 Series 1.5 E-Type OTS (Early production)
| Link: | |
| BBcode: | |
| HTML: | |
| Hide post links |