TR2/3/3A TR3A Electrical

[SteveBones]

Hello, I am a new member though I have owned TR's for a # of years. My current project is a TR3A, approximate serial # 744XX. I purchased this car 1.5 years ago as a "barn find". This means it was sitting in a garage for 10+ years. This is my first TR3. I have previously and still own newer TR series cars.

Background
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So I am close to getting it back on the road. The previous owner replaced the wiring harness. I have gone through the wiring, replaced the battery, and I am now challenged with the following:

1) I installed a New battery. Nothing happened when I turned the key and tried the dash starter button. I was able to turn the starter motor over by using the button on the starter solenoid directly (sp?).

Any suggestions on how to trouble shoot? I have a light meter. Should I use this for testing the white wires going from the fuse box to ignition switch white wires?

Should the white wires connected to the ignition switch cause the light meter to turn on if it was working correctly?

Is there a possible ground connection behind the dash that I might have overlooked?

Any help would be much appreciated.

2) The headlights, panel lights, horn, wiper motor also do not work.

3) I went through and checked the white wires from the fuse box (looks to be newer) and also checked the connections on the fuse box. I did this by checking the resistance to verify the wire.

4) In reading I have seen references to a fuse behind the dash. My car does not have one. Not sure if the PO removed this.

Thanks,

Steve

 

[TR3driver]

The white wire takes power to the fuse block, not the other way around.

I'm not sure what you mean by a "light meter"; usually they are used to check light intensity for photography. You'll need something to indicate the presence of 12v, like perhaps a 12v test light (which can be as simple as a tail light bulb with some wires soldered to it), or one of those cheap DMM (digital multimeters) from Harbor Freight.

Actually, it's probably worth picking up both if you don't already have them:
https://www.harborfreight.com/6-12-volt-circuit-tester-4288.html
https://www.harborfreight.com/7-function-multimeter-98025.html

Plus some clip leads:
https://www.harborfreight.com/18-inch-low-voltage-multi-colored-test-leads-66717.html

Easy check first (I hate crawling under the dash) : Turn the key on and check to see if there is 12v on the white wire at the fuse block. I'm guessing there isn't, but it's worth a fast check. If not, check brown wire on the other side. It gets power direct from the solenoid, so should be OK.

Next, check the A terminal on the control box (brown/white wire). If no juice here, then there is a wiring problem to the ammeter on the dash or the ammeter itself is bad. If A looks OK, check A1. If it doesn't have 12v then the control box is fried.

Now you'll have to chase the brown/blue wire from A1 to the ignition and headlight switches under the dash. Turn on each switch in turn, and see which terminals get 12v or not.

That should be enough to get you moving forward, post back here with your results.

 

[SteveBones]

Thanks for the suggested debug steps. I do have a 12v test light. Good news. I went through testing all the items you mapped out with the 12v test light with positive results.

When I connected the 12v test light to the ignition, and headlight switch, they tested positive. Also the A1 and A connectors on the regulator lit up as well. Also, the red (generator) indicator light went on and the headlamps and parking lamps lit up addition to the amp meter moved when the starter motor was turning over via the button on the starter solenoid.

Thanks for the suggestions. It saved me so much time and prevented one hugh headache.

Thanks in advance on where to go from here. Also, all the items above that were working when I pushed the starter solenoid button all stopped when I stopped pushing on button.

Thanks again!

Steve

 

[mrv8q]

In case you don't have it: wiring diagram, courtesy Dan Masters:

https://www.advanceautowire.com/tr24a.pdf

 

[TR3driver]

Also, all the items above that were working when I pushed the starter solenoid button all stopped when I stopped pushing on button.

That says to me that you have either got a bad connection in that general vicinity, or somehow the solenoid is not wired properly. The large top post on the solenoid should have the hot wire from the battery, plus the brown wire that feeds power to the rest of the car. So the brown wire should be hot even if you aren't pushing on the button.

At least on the earlier cars, those posts are an oddball British thread. If someone has tried to use a hardware store nut, that may explain the problem.

 

[SteveBones]

You nailed it. The problem is solved. The brown wire was connected to the "other" bolt connector on the solenoid that included the thick wire to the starter. After making the change you suggested, the problem was solved.

Funny in a way in that I noticed the Solenoid picture and details you posted on another tread w/o noticing the swapped connections on my car. It really helps to know where to look so Thank You again!

I do have another question regarding the wiper motor. When I pull the switch on, the amp meter is showing a lot of current (20+ amps) even though the wiper is not working. Any suggestions on what might be happening? I have taken the wiper motor off earlier but did not bench test it. Would this be the next step and what is the best way to find out if the wiper motor is working?

OK, I have a one more question. The PO switched to negative ground. When the car now has the lights on, the Amp meter swings to positive. I connected the amp meter per the wiring diagram in the book. Should I reverse to compensate for the switch to negative ground?

Thanks again. All electrical is now working including the horn and turn signals.

Steve

 

[SteveBones]

Thanks for sharing. The wire diagrams with the actual color for the wiring is extremely helpful.

Steve

 

[TR3driver]

I do have another question regarding the wiper motor. When I pull the switch on, the amp meter is showing a lot of current (20+ amps) even though the wiper is not working. Any suggestions on what might be happening?

That sounds like at least two problems. The first issue would be that the fuse did not blow. Someone may have replaced the "35 amp" Lucas fuse with a 35 amp American fuse, which is a no-no. The original Lucas fuses were rated for the current that would make them blow instantly, while the American (eg AGC) fuses are rated for the current that they will carry indefinitely. The difference is roughly 2:1 ! So if you want to use an American fuse, an AGC 20 is a closer replacement. Or you can get "proper" Lucas fuses from the usual suspects (Moss, TRF, et al).

The other problem, I'll almost bet, is that someone has wired the wiper motor wrong. Many of the wiring diagrams show the wrong information for the later cars (without indicating that it is wrong of course) and the rest of them don't include all the relevant information.

At the motor, you should find two terminals numbered 1 and 2. Terminal 2 should have one or two green wires, that are hot any time the key is on (fed through the white to green fuse in the fuse block). Terminal 1 should have a black/green wire that gets grounded through the wiper switch on the dash. Terminal 1 also gets grounded through the park switch inside the motor.

At the switch, one side should be grounded with a black wire to the tie point on the back of the dash. The other side gets the black/green wire that runs to the motor.

I would check that stuff out first, before suspecting the motor itself.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]OK, I have a one more question. The PO switched to negative ground. When the car now has the lights on, the Amp meter swings to positive. I connected the amp meter per the wiring diagram in the book. Should I reverse to compensate for the switch to negative ground? [/QUOTE]
Yup, need to reverse the ammeter connections for negative ground. The ignition coil primary terminals should be swapped as well.

 

[SteveBones]

Thanks for the suggestions regarding the wiper motor. Here is an update after following up on your suggestions:

1) The wiring appears to be correct at the wiper. T2 is where the green wire is connected. T1 is where the Black/Green wire is connected. T3 is where the black wire is connected.

2) I do have the fuses purchased from Moss installed.

3) Using the 12v test light, it did test positive at both the T2 - green and T1 green/black wire points. Is it possible that both connections would test positive if the wiper switch ground wire is not connected? I will need to look to make sure the connections are correct at the wiper switch.


Thanks again for your recommendations. So far the wiper is still not working. One other question on this. If the mechanism (mechanical) at the wiper is stuck, could this be a reason why I am seeing the current being drawn via the amp meter.

In thinking further, I remember an issue with my starter motor turning slow and the battery ground wire being hot. It was because the large ground wire from the motor to the frame was loose. It does make me believe that as you suggested it might be that the ground wire at the wiper switch is not connected. More work to be done. I might have to wait until the weekend before looking behind the dash.

Thanks,

Steve

 

[TR3driver]

Is it possible that both connections would test positive if the wiper switch ground wire is not connected?

Yes. In fact, it should be hot any time the key is on and the switch is off (assuming that the park contacts are open).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If the mechanism (mechanical) at the wiper is stuck, could this be a reason why I am seeing the current being drawn via the amp meter. [/QUOTE]
Yes, a definite possibility.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:] It does make me believe that as you suggested it might be that the ground wire at the wiper switch is not connected. [/QUOTE]That could keep the wiper motor from working, but wouldn't explain the high current draw. I was thinking more in terms of the switch being wired the way the earlier cars are, with a green wire (to power) rather than the black to ground.