How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask K. Wiggins Your Own Question
K. Wiggins
K. Wiggins, Classic Car Mechanic
Category: Classic Car
Satisfied Customers: 2631
Experience:  AA in Auto Tech, Classic car restorer and enthusiast
68360881
Type Your Classic Car Question Here...
K. Wiggins is online now
A new question is answered every 9 seconds

I tried to jump start a 71 vw fastback with the battery

Customer Question

I tried to jump start a 71 vw fastback with the battery hooked up backwards. They used a red for ground etc. Now it doesn't start. Got a new battery, but nothing works.
JA: Have you checked the battery, particularly the terminal connections? Are they corroded?
Customer: The terminals are fine. The car was perfect before i did the battery hookup wrong
JA: What is the model of your '71 VW?
Customer: fastback. type 3
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: I just got the new battery
JA: Anything else you want the mechanic to know before I connect you?
Customer: not really
Submitted: 5 months ago.
Category: Classic Car
Expert:  Mike S. replied 5 months ago.

Do you still need help with this?

If so, have you checked the fuse/links?

Customer: replied 5 months ago.
I did check the fuses. They are fine. When I was attempting to jump, the battery was literally bubbling inside. Headlights and turn signals are fine, but no click when turning the key.
Expert:  Mike S. replied 5 months ago.

Ok, at first you did say "nothing works", now you say, "Headlights and turn signals are fine". That is a huge difference.

Anyhow, since you hear no click, I assume from the starter solenoid or starter relay, then at least I know which specific circuit to be looking at now.

Do you have a voltmeter or 12 volt test light in order to do a few tests?

Customer: replied 5 months ago.
I do have a voltmeter, but am working right now. I get home around 4 pm pacific. What would you suggest I check?
Expert:  Mike S. replied 5 months ago.

If so, test for voltage to the starter solenoid/relay where the smaller gauge red wire goes for voltage when the key is on start.

Expert:  Mike S. replied 5 months ago.

I'll check back after 8pm here on the east coast where I am. I have included the wiring diagrams, in case I need to refer to them. the starter is at the top right of the second page.

If there is no voltage at the starter relay with the key on start, then the next step would be to check for voltage to the ignition switch and normally the light switch feeds power to the ignition switch. Since you said he headlights work, I assume we can rule that out but anyhow, let me know and also if this is an automatic transmission, try holding the key on start while moving the shifter all the way through all of the gears seeing if maybe the neutral switch needs adjusted, but it still sounds like a fuse popped.

Expert:  Mike S. replied 5 months ago.

I see a fuse from the fan switch feeding the light switch.

Customer: replied 5 months ago.
I tested the wires going to the solenoid. One registers no voltage with the key turned on, and the other registers -11.5 volts when the ignition is turned on. All of the fused at the dash look fine, as does the one going to the solenoid.
Customer: replied 5 months ago.
the wire registering voltage is blue. No red wires.
Expert:  Mike S. replied 5 months ago.

-11.5 volts?

I assume you mean with the key on start.

Expert:  Mike S. replied 5 months ago.

I am opting out cause I don't see any blue wire, perhaps I have the wrong wiring diagram.

Customer: replied 5 months ago.
It was with the key on start.
Customer: replied 5 months ago.
I traced the blue wire from the solenoid to a crimp with a green wire going to the distributor. They don't look original.
Customer: replied 5 months ago.
Yeah. I was testing the coil, not the solenoid. Oops.
Expert:  K. Wiggins replied 5 months ago.

Hi, did you still need help with this?

Customer: replied 5 months ago.
I know what to check, but would like an expert to walk me through it.
Expert:  K. Wiggins replied 5 months ago.

Sure thing, with the key in start check for power at the red wire coming out the ignition switch or red black at the starter solenoid. A lot of times jumping it backwards will burn up the switch, this is the quickest way to tell. Let me know what you find and we can work further if needed.

Customer: replied 5 months ago.
Thanks. I will check the red wire when I get home. I don't have a lot of time during the week, so please forgive my delays in responding.
Expert:  K. Wiggins replied 5 months ago.

No problem at all.

Related Classic Car Questions