My AM car radio has tons of static when the engine is running. The thing is useless when the car is on or even if the key is turned to the on position right before you start the car. It's fine if you turn the key to the aux position.
Another clue...
When I turn an electrical motor in the car on and off, it sometimes reduces the static level...but never eliminates it. And then when I've fiddled with something and reduced the static, I'll hit the brakes, and the brake light will trigger the static onslaught again.
I have taken the radio out, and checked the antenna connection as well as used jumper cables to ground the grounding bolt. No significant improvement.
Manufacturer's original equipment or some third party installation? It simply takes an antenna plug not exactly sized to the radio socket. That intermittent connection then creates radio static. There are a long list of other reasons including loose ground to chassis. There is very good reason why grounds are not just put anywhere. Does the antenna coax shield somewhere make contact with the chassis ground? That too would create static problems.
Your car radio should receive major (50,000 watt) AM radio stations even 100 miles away. If not, your radio may be a discount special, or you have loose connectors, or other possibilities are just too numerous to mention here.
Remember wire is just another antenna. Even where a radio is grounded > My AM car radio has tons of static when the engine is running. The
Or the regulator inside the alternator is a source of RF. There are just too many other potential reasons to but only blame a computer or instrument cluster.
Cars do not come from the factory with static. Number > the cars onboard computer or instrument cluster is generating RF.
When you checked the antenna, did you also verify that the antenna coax outer shield made a good connection to ground at the base of the antenna? It is important that BOTH antenna lead conductors be connected well.
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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
Thanks for all the advice. Let me fill in some more details. The radio is OEM in a 95 Jeep Grand Cherokee Limited. It has some sort of amplified output and an electric antenna. The problem has been more progressive than sudden. Only affects reception when the car is 'on' (running or key in the on position). The antenna is original, and the connection to the radio appears good. Something else not grounded and giving off static is a possibility...would have to be something that powers up just with the 'on' switch, not just when running (may eliminate alternator). If it is a 'ground leak,' might that explain how sometimes fiddling with an electric switch seems to reduce the static? Maybe the other switch grounds some of the static causing emission? Not really knowledgeable about electronics.
You are still making assumptions without facts. For example, if the key is on but engine not running, then regulator electronics inside the alternator can still be radiating RFI. Obviously. Engine need not be turning for those electronics to be functioning.
Furthermore, its not about something "not grounded and giving off static". It can also be "something grounded differently and therefore radiating noise". Noted earlier - every ground wire is also an antenna. Vehicle electronics must be grounded to work. Therefore even working electronic device that radiates noise is also grounded.
There is no way to visually confirm a connection - "the connection to the radio appears good" and yet that antenna connection is not between two connectors of the same size. A failed antenna wire connection will always 'appear good'.
Welcome to an art where you cannot make blanket assumptions. Your first efforts should only be on confirming antenna integrity as I and Jim Adney have noted. This, of course, assumes everything is original Jeep equipment - a necessary fact which has not been stated. For example, if that amp is after market, then there is a grounding change - or other problem.
Aga> Thanks for all the advice. Let me fill in some more details. The radio
Given that it is a Chrysler product, likely with the Infinity sound system. There is a very good chance the the ground to the fuel pump, power regulator, or other main system ground in the car has become corroded and is no longer a good ground.
I have fixed a couple with bad ground to the fuel pump or the blower motor that was causing radio interference in the past. Ground would read a few small ohms resistance, but it was enough for the motor noise to be radiated and the motor would still run.
Your are on the right track.> we need to know if the noise changes with engine speed, vehicle speed, interior lights on, esterior lights on, doors open or closed to light the interior lights, etc. A bad ground on some other piece of equipment is the most likely item. My Nissan pathfinder makes AM radio weak stations clicks as a function of vehicle speed. It must be the electronic odometer, and I have learned to live with it. I have seen bad fuel pump grounds, ceiling lights with poor grounds, etc. Sionce this vehicle has an electric antenna (presumable to make it go up and down, I would look for a poor ground connection in the vicinity of the antenna and along the route the antenna wire takes from the antenna to the radio. ALso, as one poser said, take a small transistor radio, tune to a weak station, and sniff around the vehicle to see if you can pick up any noise that sounds like the noise on the radio. Good detective work will eventually find the answer.
As an EMC engineer with 40+ years of experience, once you find the trouble, it will be obvious what is going on. I once tracked a malfunctioning electronic telephone office source of problems to trains turning their transmitters on to call the dispatcher just as they went past the back of the telephone office. The malfunctioning processor only happened when the transmitters on the trains were turned on at a particular spot where the antenna pointed right at the telephone office as the train went by. A little conductive paint on the back wall of the telephone office provided enough shielding to stop the problems. SO, anything is possible.
Since my last post, I have tried a number of things to try to isolate the issue. I connected a new (non-electric) antenna, and grounded it directly to the battery. I had the radio on w/lots of static and pulled each fuse (including fuel pump) one by one. I had a jumper cable on the battery ground and conected it to the alternator, engine computer, sound amp and radio ground itself.
None of these made any improvement.
I'll try grounding the fuel pump as I could not easily locate it yesterday.
As to other questions posted here...nothing else in the vehicle seems to correlate with less or more static. But it is worse sometimes than others. Which may be a result of the weather or other conditions making for a better or worse ground connection somewhere.
The extreme noise problem significantly points to a broken ground connection in the antenna circuit somewhere. The broken ground may be inside the radio. You might open the radio case and closely inspect the antenna circuit connections. You might find the shield connection broken where the antenna connector or the coax cable from the antenna connector makes the connection to the radio's PCB.
As an alternative, park a car with a normally operating radio close to your car. Shut the other car off and start your car. Do you hear the noise in the other car's radio? If so, the problem is probably in your car's high voltage ignition circuit. Check the ignition coil, distributor, the spark plug wires and the plugs.
Cheers!!
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Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)
Never take a laxative and a sleeping pill at the same time!!
Appreciate what was said about wire. The battery ground and radio ground may be same to 12 volts DC. But they are completely different to RF - your static noise. Grounding the antenna to the battery would only worsen the problem. Grounding the antenna to the battery suggests you are not learning the underlying principles posted by others. Battery ground and radio ground are different - as far as the antenna is concerned.
Antenna ground must be to radio ground. A previous post also about how coax ground wire must not contact other ground such as chassis was making the same point. The radio ground is connected to ground directly at the base of the antenna - for same reason. And again, the antenna coax wire connector may 'look' connected to radio antenna socket - and yet still not be connected.
Even possible that the antenna socket inside the radio has a cracked solder joint - therefore the antenna ground is not connected to radio.
Again, you still have not specifically listed what is installed from factory and what is after market - only making it more difficult for every reply to be helpful. Where did that amp come from? How is it grounded?
Of course you already have the Jeep's wiring diagram. You cannot be locating this problem (easily) without a wiring diagram.
For example, along with what hrhofmann posted: is it an electric fuel pump? Fuel pump is not always on. You should have learned that by now in you search for the noise source. For example, pump often turn on only for a few seconds after key goes to on. Then if no engine requirement for fuel, the electric fuel pump turns off. Does the noise go on and off with fuel pump?
Pull the fuse that is only for alternator regulator. Does noise disappear? Same for engine computer. To accomplish anything from this trick, again, that wiring diagram is necessary since even some disconnects may not fully remove power as you assume. You cannot assume anything. The vehicle has many computers - not just an engine computer. Any one could be a noise source. Vehicle has something like 50 motors. Which motor is always on only when noise is created.
The transistor radio idea also works as long as you don't assume a linear relationship between volume of noise on radio and amplitude of noise. You have not even told us if noise is radiated, if it is common mode, or if it is differential mode on AC wires. Just another part of breaking the problem down into parts.
D> Since my last post, I have tried a number of things to try to isolate
an alternative is to build a "sniffer" antenna. this is a small loop antenna wound at the end of non conductive rod. the coax connects to the car radio (or a portable) you fish around the engine with this in relative safety looking for the spot that makes the loudest similar noise.
for what it worth my 2000 cherokee exhibits similar issues. i get clicks and pops when turn signals are in operation. sometimes when wipers are in operation. i find that the added interference make Rush Limbaugh slightly more palatable.
an alternative is to build a "sniffer" antenna. this is a small loop antenna wound at the end of non conductive rod. the coax connects to the car radio (or a portable) you fish around the engine with this in relative safety looking for the spot that makes the loudest similar noise.
for what it worth my 2000 cherokee exhibits similar issues. i get clicks and pops when turn signals are in operation. sometimes when wipers are in operation. i find that the added interference make Rush Limbaugh slightly more palatable.
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