can i assume that with this modern cassette/radio in the dash that the car has been converted to negative ground?

 

Stu just open the bonnet and see which cable is earthed--no need to guess.

 

I wish I knew more about the whole positive / negative ground issue. I assume if your car is positive ground, and the radio works, then it is either set up for positive ground or like many parts, it works either way. Radios are funny though. I have an older one I am putting in my car set up for positive ground. Looks the same. Jut hope I don’t blow it up.

 

Ummm.
As George says...

My dad had a 63 P5 Rover and that radio cold be switched to work either or.
He did change it to Negative ground and forgot about the radio.
It didn't last long.

Radios are not like light bulbs, they can't be simply changed back and forth.

It doesn't matter which way the current flows through a light bulb filament, it will still light up.
But a radio is much more complicated then a light bulb.

 

Jeff right--I have a couple of old PYE radios with the switch plug to change polarity But radios are like light bulbs in that if you hook them up wrong you may get a brief LIGHT! Then smoke.

 

Generally but not always Radio's are polarity sensitive, however if there is a bridge rectifier across in input, then they can be connected either way, the input is then not polarity sensitive, but the inner workings of almost any radio is, the bridge rectifier does the polarity switching for you just inside the radio.

Chuck, if your radio IS polarity sensitive, then you will surely fry it if it is connected the wrong way. How old is the radio you are planning on using ?

Some of the capacitors will probably be polarity sensitive, and if they are connected the wrong way round, they will go up in smoke and can actually catch fire ! Transistors and semiconductors will generally just pop without too much fuss, but capacitors can be a fire hazard if connected the wrong way.

Chuck if your radio is reasonably old (10 years or more) you may be able to check for a bridge rectifier by looking inside the radio, but if it is modern, the the components are more difficult to distinguish, but there may be circuit diagrams online that will tell you.

If you let me know what the radio is Chuck I may be able to find out, or explain exactly what a bridge rectifier is so you can look inside yourself.

As Jeff said, Radios are NOT like light bulbs !

 

Wish that would do it. I'll check but the guy who had it right before me noodle stuff around because of the no start issue.

 

I don't understand what the problem is.
Even if there was no battery in place to determine positive or negative ground, the terminal on the battery are different sizes.

They can only connect one way, that should tell you.

From what I can tell, the radio is Pioneer.
Pull the radio, and if there is a device to change it, it will be on the chassis somewhere, on one of the sides near the back.

The radio out of my Dad's P5 Rover had a round fibre like disc that you turned with a screw driver. You could point it to + or -...

The radio may also be isolated from the cars chassis, in that case, the radio would be negative ground.

 

if the ground cable (the cable which is bolted to the BODY near the bonnet Hinge), is connected at the N (-) pole of the Battery, it has been changed to Negative Ground.

 

If you are not sure if the previous owner has changed stuff about without actually changing the polarity properly, check everything that should be changed.

Coil polarity
Fuel Pump
Ammeter
etc.

If these are all either positive or negative earth, then that will be the answer, either connect the battery to suit the ancillaries, or change the ancillaries to suit the battery, if you change the ancillaries, re polarize the dynamo before trying to start the car.