Testing electrical without a engine

[A70Runner]

Anyone ever hook the battery up without a engine in the car? I have all new wiring front to rear on my car. I would like to test everything(lights etc. ) before I put the carpeting and seat back in. The engine isn’t ready to reinstall yet. Anyone ever done this?

 

[pnora]

I do it all the time.

 

[451Mopar]

Just make sure the engine harness connectors are not touching the body/ground.
Just wrap electrical tape over the connector ends, mainly the alternator output wire, and all the ignition power connections (examples like ballast resistor, coil, choke, regulator, alternator field) are the major ones where a short would/should blow the fusible link if grounded. The other connectors, like temp and oil gauge should also be isolated, but those shorting out will max out the gauge readings (or turn on the oil light) if grounded.

 

[mr. b]

i do it on all the cars i build i use a battery charger

 

[451Mopar]

My newer battery charger won't even output power unless it detects it is connected to a battery.
The old electronics may not be sensitive to voltage spikes and noise from the battery charger.
I would not use a charger (without battery connected) to check modern electronic circuits.
Most electronics should be able to protect themselves from possible voltage spikes (to a point), but the noise might cause the electronic devices to trigger/re-set and result in inaccurate test results. Most likely not an issue for our old cars unless modifying the vehicle to use CAN bus power modules, and newer infotainment and alarm systems.
I have used a Li-battery jump pack because it is small and light weight (compared to an actual car battery), but it puts out 16 volts.

 

[Mike67]

You would probably need to run a ground if testing sensors/gauges back to the battery( pressure/temp).

 

[AR67GTX]

I test components (clocks, gauges, dash lights, fan motors, radios, etc) with jumpers off a car battery all the time. Shouldn’t have any problem in a motor less car for most accessories and lights as long as all grounds are made.

 

[Pistol Pete]

I use a small 12v dry cell to test stuff, but I run it off of a circuit breaker should something be/get grounded. Keeps the light show to a minimum.

 

[69 GeeTeeX]

I’ve done it several times. I have short pieces of rubber hose cut to slide over wiring and tape in place so they can’t ground out. Never had a problem.

 

[4mulas]

If you have an ohm meter with audible feature you can just test circuit continuity. I do that quite a bit.

 

[Dean Prevolos]

Anyone ever hook the battery up without a engine in the car? I have all new wiring front to rear on my car. I would like to test everything(lights etc. ) before I put the carpeting and seat back in. The engine isn’t ready to reinstall yet. Anyone ever done this?

I was also going to test my new wiring with a new battery BEFORE I install the engine. Great post with excellent comments from everyone. Thanks to all!

 

[Nacho-RT74]

Just need to isolate the alt wire and you will be done. You can test everything like the engine is in place. The alt wire is the only one what really needs to be isolated, since is a direct path to the batt ( throught the ammeter into the cab ), and even stock alt wire gets a plastic sleeve around, hole is huge enough to accidentally get in touch with any body part around. Nothing else really needs to be isolated.

Of course to test oil and temp gauges will need to ground the temp and oil sender wires. It will go up to max reading

 

[Dean Prevolos]

Just need to isolate the alt wire and you will be done. You can test everything like the engine is in place. The alt wire is the only one what really needs to be isolated, since is a direct path to the batt ( throught the ammeter into the cab ), and even stock alt wire gets a plastic sleeve around, hole is huge enough to accidentally get in touch with any body part around. Nothing else really needs to be isolated.

Of course to test oil and temp gauges will need to ground the temp and oil sender wires. It will go up to max reading

Thanks for the detailed explanation. Much appreciated.

 

[Nacho-RT74]

Oh... allmost forget! Also the starter motor wires! Not really the solenoid wire but the thick one, althought being both tied together, isolate both will be pretty much the same

 

[Dean Prevolos]

Oh... allmost forget! Also the starter motor wires! Not really the solenoid wire but the thick one, althought being both tied together, isolate both will be pretty much the same

ok