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I think I opened a big old can of worms
I have been having a lot of problems with a whining noise in my radio and
CB. I've put a filter on the power lines and hooked it directly to the battery with no luck. So being the "I want to fix it all" type of guy, I started looking under the hood for a bad ground. Well I have replaced the engine, carb, distributor, and gotten rid of all the emissions stuff and there were a lot of connectors tie rapped to the fire wall where I left them after disconnecting them. Well I started to pull the unused wires out. After 3 hours and a couple of dozen wires the Jeep started. The only problem is the Tac will not work, so here are my questions: Where does the tac get its signal from? What are the 2 relays, 2 capped connectors, and 4 wire circuit board that are between the fender and the battery? Next I want to go under the dash and remove the computer and all the crap under there, what is the easiest way to get it out?? Well I'm back to it tomorrow, thanks in advance for all advice. Scott 90YJ 4.2L AX15 |
Re: I think I opened a big old can of worms
The tach on a YJ 258 gets it's signal from the computer.
I was told you can just move the tach pickup wire to the coil to finish dumping the computer in the garbage. On a CJ7 258, the tach is inline with the ignition module power. One of those relays powers up the manifold heater and tags the electric choke via the oil pressure switch. The other one 'might' be an idle relay to turn on the sol-vac for an auto or air. It would need the computer working to fire. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Foot Loose wrote: > > I have been having a lot of problems with a whining noise in my radio and > CB. I've put a filter on the power lines and hooked it directly to the > battery with no luck. So being the "I want to fix it all" type of guy, I > started looking under the hood for a bad ground. Well I have replaced the > engine, carb, distributor, and gotten rid of all the emissions stuff and > there were a lot of connectors tie rapped to the fire wall where I left them > after disconnecting them. Well I started to pull the unused wires out. After > 3 hours and a couple of dozen wires the Jeep started. The only problem is > the Tac will not work, so here are my questions: > > Where does the tac get its signal from? > > What are the 2 relays, 2 capped connectors, and 4 wire circuit board that > are between the fender and the battery? > > Next I want to go under the dash and remove the computer and all the crap > under there, what is the easiest way to get it out?? > > Well I'm back to it tomorrow, thanks in advance for all advice. > > Scott > 90YJ > 4.2L AX15 |
Re: I think I opened a big old can of worms
The tach on a YJ 258 gets it's signal from the computer.
I was told you can just move the tach pickup wire to the coil to finish dumping the computer in the garbage. On a CJ7 258, the tach is inline with the ignition module power. One of those relays powers up the manifold heater and tags the electric choke via the oil pressure switch. The other one 'might' be an idle relay to turn on the sol-vac for an auto or air. It would need the computer working to fire. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Foot Loose wrote: > > I have been having a lot of problems with a whining noise in my radio and > CB. I've put a filter on the power lines and hooked it directly to the > battery with no luck. So being the "I want to fix it all" type of guy, I > started looking under the hood for a bad ground. Well I have replaced the > engine, carb, distributor, and gotten rid of all the emissions stuff and > there were a lot of connectors tie rapped to the fire wall where I left them > after disconnecting them. Well I started to pull the unused wires out. After > 3 hours and a couple of dozen wires the Jeep started. The only problem is > the Tac will not work, so here are my questions: > > Where does the tac get its signal from? > > What are the 2 relays, 2 capped connectors, and 4 wire circuit board that > are between the fender and the battery? > > Next I want to go under the dash and remove the computer and all the crap > under there, what is the easiest way to get it out?? > > Well I'm back to it tomorrow, thanks in advance for all advice. > > Scott > 90YJ > 4.2L AX15 |
Re: I think I opened a big old can of worms
Easiest way to eliminate non-RF electrical noise (at least that I have
found) is to use a .1uf mylar cap to ground from the B+ line. It helps to add one at the closest practical point to the radio, and others at the offending devices (motors/alternators) be sure to restrain the cap properly, and insulate the leads. Not perfect, but simple, and eliminates most noise sources. tach picks up signal from switched side of coil. "Foot Loose" <footloose61@ NOSPAM hotmail.com> wrote in message news:NGw7b.7831$cQ1.2249605@kent.svc.tds.net... > I have been having a lot of problems with a whining noise in my radio and > CB. I've put a filter on the power lines and hooked it directly to the > battery with no luck. So being the "I want to fix it all" type of guy, I > started looking under the hood for a bad ground. Well I have replaced the > engine, carb, distributor, and gotten rid of all the emissions stuff and > there were a lot of connectors tie rapped to the fire wall where I left them > after disconnecting them. Well I started to pull the unused wires out. After > 3 hours and a couple of dozen wires the Jeep started. The only problem is > the Tac will not work, so here are my questions: > > Where does the tac get its signal from? > > What are the 2 relays, 2 capped connectors, and 4 wire circuit board that > are between the fender and the battery? > > Next I want to go under the dash and remove the computer and all the crap > under there, what is the easiest way to get it out?? > > Well I'm back to it tomorrow, thanks in advance for all advice. > > Scott > 90YJ > 4.2L AX15 > > |
Re: I think I opened a big old can of worms
Easiest way to eliminate non-RF electrical noise (at least that I have
found) is to use a .1uf mylar cap to ground from the B+ line. It helps to add one at the closest practical point to the radio, and others at the offending devices (motors/alternators) be sure to restrain the cap properly, and insulate the leads. Not perfect, but simple, and eliminates most noise sources. tach picks up signal from switched side of coil. "Foot Loose" <footloose61@ NOSPAM hotmail.com> wrote in message news:NGw7b.7831$cQ1.2249605@kent.svc.tds.net... > I have been having a lot of problems with a whining noise in my radio and > CB. I've put a filter on the power lines and hooked it directly to the > battery with no luck. So being the "I want to fix it all" type of guy, I > started looking under the hood for a bad ground. Well I have replaced the > engine, carb, distributor, and gotten rid of all the emissions stuff and > there were a lot of connectors tie rapped to the fire wall where I left them > after disconnecting them. Well I started to pull the unused wires out. After > 3 hours and a couple of dozen wires the Jeep started. The only problem is > the Tac will not work, so here are my questions: > > Where does the tac get its signal from? > > What are the 2 relays, 2 capped connectors, and 4 wire circuit board that > are between the fender and the battery? > > Next I want to go under the dash and remove the computer and all the crap > under there, what is the easiest way to get it out?? > > Well I'm back to it tomorrow, thanks in advance for all advice. > > Scott > 90YJ > 4.2L AX15 > > |
Re: I think I opened a big old can of worms
"Jerry Bransford" <jerrypb@mecox.net> wrote in message news:nXP7b.48498$Qy4.27613@fed1read05... > Electrical noise or sound is AC (alternating current) and a capacitor passes > AC and blocks DC. So if you connect a capacitor between the + power lead > and ground, the capacitor will pass the AC noise component riding on the DC > voltage to ground. > > A capacitor with a rating of 25 volts or higher will be fine. Electrolytic > capacitors are the best type for this application... you can tell an > electrolytic capacitor by the leads being marked + and -. The bigger the > capacitor, the better filtration it provides. An electrolytic cap may not have a low enough ESR (equivalent series resistance) at the frequency of interest... they are also polarized, so if you hook one up backwards, you will either have not much capacitance (best case) or it will explode like a firecracker (what usually happens). Best thing to do is to put *both* a big e-lytic and a small (.1uF) cap across the alternator output (big red wire) and ground. There are special caps called 'feedthrough' that can be spliced into the big wire and grounded. You really should first determine whether the noise is coming in the antenna lead, or the power supply wire. This is easily done by disconnecting the antenna and seeing if any improvement is noticed. If this helps, you need to address the noise at the source, usually the alternator or distributor/coil. If the noise is coming in the power lead, you can install a noise suppressor, available at Rat Shak. This consists of an inductor (like a transformer, a coil of wire around a piece of iron) that will allow DC to pass but blocks AC. You put it in series with the power lead going to the radio, follow the directions. __ Steve .. |
Re: I think I opened a big old can of worms
"Jerry Bransford" <jerrypb@mecox.net> wrote in message news:nXP7b.48498$Qy4.27613@fed1read05... > Electrical noise or sound is AC (alternating current) and a capacitor passes > AC and blocks DC. So if you connect a capacitor between the + power lead > and ground, the capacitor will pass the AC noise component riding on the DC > voltage to ground. > > A capacitor with a rating of 25 volts or higher will be fine. Electrolytic > capacitors are the best type for this application... you can tell an > electrolytic capacitor by the leads being marked + and -. The bigger the > capacitor, the better filtration it provides. An electrolytic cap may not have a low enough ESR (equivalent series resistance) at the frequency of interest... they are also polarized, so if you hook one up backwards, you will either have not much capacitance (best case) or it will explode like a firecracker (what usually happens). Best thing to do is to put *both* a big e-lytic and a small (.1uF) cap across the alternator output (big red wire) and ground. There are special caps called 'feedthrough' that can be spliced into the big wire and grounded. You really should first determine whether the noise is coming in the antenna lead, or the power supply wire. This is easily done by disconnecting the antenna and seeing if any improvement is noticed. If this helps, you need to address the noise at the source, usually the alternator or distributor/coil. If the noise is coming in the power lead, you can install a noise suppressor, available at Rat Shak. This consists of an inductor (like a transformer, a coil of wire around a piece of iron) that will allow DC to pass but blocks AC. You put it in series with the power lead going to the radio, follow the directions. __ Steve .. |
Re: I think I opened a big old can of worms
Approximately 9/10/03 18:00, Michael Vincenty uttered for posterity:
> Hey, maybe you can offer me a bit of assistance on a similar problem (not a > Jeep - sorry). I too have been trouble-shooting a similar problem with an > 89 GMC C1500 which has an alternator whine coming from the radio (changes > with engine RPMs). > > The factory service manual says to try and install a 250 MFD (100 V) > capacitor on the alternator output lead and/or brown field wire to the > ground. I tried this and it did not work. If I am reading your post > correctly, you are recommending installing a .1 microfarad capacitor on the > battery postive lead into the radio and ground (as close as possible to the > radio as possible). Is that correct? Does voltage matter as long as it is > at least 12 volts? Do you know how installing a capacitor works to > eliminate the whine (just was wondering)? Two problems with a capacitor as big as 250 mfd. One is that unless it is non-polarized [as in an audio specialty capacitor] it is too easy to put in backwards... which is no biggie as unless it is a non-polarized one, it acts as a rectifier and not a capacitor for roughly one-half the noise. It is also a bit large, but I doubt if it presents much of a load on the alternator. The other problem with large caps like this is that they tend to be bothered by heat more... and even worse, if it is a Tantalum cap, if it ever fails it has roughly as good odds failing to a short as it does to an open. Knock wood if it fails to a short it is wimpy enough the alternator/battery combination turns it into a flashbulb for a few seconds, then it is out of the circuit. The only cost effective way to make really big capacitor values is to make electrolytic types. Normal ones are polarized and not particularly good under heat. If you have an audio specialty shop in the area, swap that cap with a 250 Microfarad Non-polarized capacitor with at least a 50 volt rating. These are often found in speaker crossover networks. And with a cap that large, you then need to bypass the cap with an RF passing cap.... a .1 to .01 microfarad plastic works reasonably well, again get at least a 50 volter. Mylar, polystyrene, etc. For alternator whine, it usually works better to tie several .1 or even .01 mfd mylars from +12 to ground along the power path to the radio. SOMETIMES you can use very short jumpers to try spots to mount them, just stick one lead on the +12 and the other to a nice clean ground. The good news about these is that they are non-polarized. Warning that sometimes you also get RF from the alternator radiated to the antenna wiring if that antenna wiring is at all loose and/or poorly grounded. You can safely bypass the *outer* conductor of a coax antenna lead to ground, but don't try it with the center lead. Warning that bypassing audio noise is as much black magic and luck as science. |
Re: I think I opened a big old can of worms
Approximately 9/10/03 18:00, Michael Vincenty uttered for posterity:
> Hey, maybe you can offer me a bit of assistance on a similar problem (not a > Jeep - sorry). I too have been trouble-shooting a similar problem with an > 89 GMC C1500 which has an alternator whine coming from the radio (changes > with engine RPMs). > > The factory service manual says to try and install a 250 MFD (100 V) > capacitor on the alternator output lead and/or brown field wire to the > ground. I tried this and it did not work. If I am reading your post > correctly, you are recommending installing a .1 microfarad capacitor on the > battery postive lead into the radio and ground (as close as possible to the > radio as possible). Is that correct? Does voltage matter as long as it is > at least 12 volts? Do you know how installing a capacitor works to > eliminate the whine (just was wondering)? Two problems with a capacitor as big as 250 mfd. One is that unless it is non-polarized [as in an audio specialty capacitor] it is too easy to put in backwards... which is no biggie as unless it is a non-polarized one, it acts as a rectifier and not a capacitor for roughly one-half the noise. It is also a bit large, but I doubt if it presents much of a load on the alternator. The other problem with large caps like this is that they tend to be bothered by heat more... and even worse, if it is a Tantalum cap, if it ever fails it has roughly as good odds failing to a short as it does to an open. Knock wood if it fails to a short it is wimpy enough the alternator/battery combination turns it into a flashbulb for a few seconds, then it is out of the circuit. The only cost effective way to make really big capacitor values is to make electrolytic types. Normal ones are polarized and not particularly good under heat. If you have an audio specialty shop in the area, swap that cap with a 250 Microfarad Non-polarized capacitor with at least a 50 volt rating. These are often found in speaker crossover networks. And with a cap that large, you then need to bypass the cap with an RF passing cap.... a .1 to .01 microfarad plastic works reasonably well, again get at least a 50 volter. Mylar, polystyrene, etc. For alternator whine, it usually works better to tie several .1 or even .01 mfd mylars from +12 to ground along the power path to the radio. SOMETIMES you can use very short jumpers to try spots to mount them, just stick one lead on the +12 and the other to a nice clean ground. The good news about these is that they are non-polarized. Warning that sometimes you also get RF from the alternator radiated to the antenna wiring if that antenna wiring is at all loose and/or poorly grounded. You can safely bypass the *outer* conductor of a coax antenna lead to ground, but don't try it with the center lead. Warning that bypassing audio noise is as much black magic and luck as science. |
Re: I think I opened a big old can of worms
Approximately 9/10/03 18:09, Jerry Bransford uttered for posterity:
> Electrical noise or sound is AC (alternating current) and a capacitor passes > AC and blocks DC. So if you connect a capacitor between the + power lead > and ground, the capacitor will pass the AC noise component riding on the DC > voltage to ground. > > A capacitor with a rating of 25 volts or higher will be fine. Electrolytic > capacitors are the best type for this application... you can tell an > electrolytic capacitor by the leads being marked + and -. The bigger the > capacitor, the better filtration it provides. > Polarized electrolytics are bypass caps for one direction of flow and rectifiers in the other. A quick and dirty way to solve this is to parallel two with leads reversed... and oddly enough you can also series connect them with the two negative leads, but you get half the capacitance. Personally I'd go for 2.5 times max voltage which gets closer to 50 volt than 24, with 100 volts not being overkill. And normally recommend bypassing any electrolytic with a .01 or so mylar, etc. |
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