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I need to take a three hour trip later this afternoon to pick up the boy at school so I figured this would be a perfect opportunity to put a few miles on the new clutch in our 91B. On the way to work this morning, I started hearing a steady ticking behind the dash and the radio stopped working. It sounded like a failing relay to me so I pulled over to check it out. I believe I touched every relay easily accessible under the dash and in the fuse panel, but none of them seemed to be the ticking culprit.

I don't have my CarDisc at work so I thought I'd see if you gents could help. Looking through some of the older posts, it sounds like there's a specific radio relay somewhere behind the instrument cluster. Anyone know for certain where it is and how to easily get to it? While I would be perfectly content listening to the wonderful sound of the V6 instead of the radio this afternoon, I don't know if I can handle three hours of that ticking - it's pretty darn loud.

Thanks in advance.

Walter
 

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Yes, you have to remove the gauge cluster to get to it. You could pull the radio fuse, I suppose, to cure the ticking for now.
Charles
 

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I need to take a three hour trip later this afternoon to pick up the boy at school so I figured this would be a perfect opportunity to put a few miles on the new clutch in our 91B. On the way to work this morning, I started hearing a steady ticking behind the dash and the radio stopped working. It sounded like a failing relay to me so I pulled over to check it out. I believe I touched every relay easily accessible under the dash and in the fuse panel, but none of them seemed to be the ticking culprit.

I don't have my CarDisc at work so I thought I'd see if you gents could help. Looking through some of the older posts, it sounds like there's a specific radio relay somewhere behind the instrument cluster. Anyone know for certain where it is and how to easily get to it? While I would be perfectly content listening to the wonderful sound of the V6 instead of the radio this afternoon, I don't know if I can handle three hours of that ticking - it's pretty darn loud.

Thanks in advance.

Walter

Walter,

Radio relay I70 behind instrument cluster 2nd from left. Troubleshoot buzzing relay by pulling 10A F5 fuse in G2 small aux fuse box above main fuse box. That should disable relay energize solenoid. Fuse for power antenna, radio relay I70 and door open, trunk lighting, etc.
 

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Does your car have an aftermarket radio? When I tried to put a CD player in mine, I got the same ticking going on as you have, put the original back in and the ticking stopped. So I installed it in my Ram, using the same Chrysler harness. When I go to put another CD player in eventually, I'm going to rewire it so that the relay isn't used, which should be easy enough.
Charles
 

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Bouncing relay

Yes, the installation of an after market radio might cause this relay clicking problem!

We got this problem after my son put in an after market radio. Here's what basically happened (from my memory). When you switch on the ignition, power is supplied to the radio (radio is left ON). The radio routes the power to another wire (I recall it is the same wire that powers the antenna). This wire flips the radio relay and now the radio is powered from another power path (not the ignition ON one). This way, the radio will still be ON even if you turn the ignition key back to OFF without pulling the key out - so you can listen to the radio while waiting for someone! Now, the problem with some after market radio is that it does not have enough capacitance between the main power wire and the antenna wire to handle the switch over (of the power source) like the stock radio can. The antenna/output power wire would drop power before the relay is fully latched. When it does that, power supply is back to the ignition ON wire and the radio supplies power to the antenna wire again. This back and fore is causing the relay clicks and radio going ON and OFF. My solution: I added a small capacitor to the output power wire to help the transition - works fine since!
 

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Discussion Starter #6
Gentlemen,

Thanks for the wealth of info. It is an aftermarket radio in the car. I was thinking of replacing the unit at some point and it might be a good idea to add that capacitor to the output line for added insurance when I do.

Steve and Charles - I found the referenced fuse when I went out at lunch, but then remembered how easy it was to remove the instrument cluster so I took an extra two minutes and did that. I easily found the offending relay ticking away and replaced it with one of the salvage-yard spares I keep in a zip-lock in the trunk. That took care of it.

Thanks to your lightening quick and thorough responses, I'll be listening to both the V6 and the traffic reports on my little road trip this afternoon.

Thanks again and have a great 4th!

Walter
 

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I'm actually surprised another relay fixed it. I swapped one out on mine with the same clicking and the radio going off and on. BlackAlfa, that sounds like a good fix. I assume you mean add a small capacitor (you mean like a 1 or 2 mf cap) inline with the antenna/amp ON signal (normally blue) wire?
Charles
 

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I'm actually surprised another relay fixed it. I swapped one out on mine with the same clicking and the radio going off and on. BlackAlfa, that sounds like a good fix. I assume you mean add a small capacitor (you mean like a 1 or 2 mf cap) inline with the antenna/amp ON signal (normally blue) wire?
Charles
Perhaps there is some difference between relays in terms of power draw (by the coil) and/or response time (to get fully latched)!

I don't remember what value I used. It is probably not too critical as long as it is not too big (that will take the radio awhile to charge it up) or too small (not enough). You can cut some drum shape capacitors out from some unwanted electronics (like motherboards or power supplies) and try them.

The power supply wire to radio is the LTBLU-RED wire. The radio power output line (either for antenna or amp) should drive the YEL-RED wire. This YEL-RED wire will flip the radio relay I70 to switch power source (from hot-in-run to hot-all-times). To add a capacitor, I would connect one leg of the capacitor to the YEL-RED wire and the other leg to ground. When the YEL-RED wire gets power, the capacitor gets charged up and it will holds the voltage up a little to allow the relay to get fully latched even if the radio drops power to the YEL-RED wire during the transition.
 

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OK, I got ya. I have a couple of 120,000 mf caps I used years ago as "stiffening caps" for a power amp. Do you think those might be too big? Just kidding! ;) I believe I have some small caps around I could use. This has been very useful info, so thank you very much. I will be installing a CD player soon. I'm sure, pretty tired of the old Chrysler radio and I have already upgraded the speakers with some Acoustic Research in the front and Polks in the back so just need the headunit upgrade. Maybe I'll swing for an Alpine since I am not a fan of the Blaupunkt that I bought. It's just too "German" not intuitive to operate at all.
Charles
 

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Wow I have had quite a few 164's and never had a problem. Not with the crappy stock radio and even with the crappy Dodge c/d radio to high end Alpine/Pioneer ETC they all worked without a problem....I guess that I have been lucky to date? A relay on the radio is not good though might be a good idea to bypass just to be sure.
 

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The only purpose of that I70 radio relay is to allow one to use the radio/CD with the ignition key in the OFF position (after it had been in the ON position before). When the key is pulled, the radio is OFF. Think about how the relay works! To ensure isolation of the two contacts (the two power source paths in this case), there is a very, very short moment when the swing/contact arm is in between the two contacts. At this moment, power to the radio is cut off (not in contact with either power sources). So unless the radio has some built in capacitance, the output power lines (antenna or amp - I think these are more like low power signal lines for a lot of radios) will not be able to provide enough residual power to sustain the transition causing the relay to go back to its rest/default position.

Yes, one can alternately bypass the relay but the factory behavior will be lost:

1. Wire the power source directly to ignition ON (hot-in-run). The radio will turn ON and OFF with the ignition key and it will not stay on in the ignition OFF position.

2. Wire the power source directly to battery (hot-always). The radio will be independent and not controlled by the ignition key. If you do this, just remember to turn the radio OFF when you park or it will keep on draining the battery - especially if you have a mega-watts power subwoofer amp in the trunk ;)!
 
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