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My 1996 Chrysler T&C's horn started failing a year or so ago. 1st one horn died. I removed it and it was open (infinite resistance). A month or 2 ago the 2nd horn died. Found that horn fuse was burnt. Replaced fuse and horn worked briefly, then died again. I knew I needed a new horn so I bought and replaced the pair -- but new horn set wouldn't work. Found burnt fuse again. Replaced fuse again and it almost immediately burnt out (without horn even honking this time.)
Measured voltage at fuse socket: When ignition is OFF, 12V at bottom of socket, 0V at top and 10 Kohm from top to gnd. When ignition is ON, 12 V at bottom of socket and no resistance from top to ground. I assume fuse is blowing when the ignition goes ON.
Is my problem in the horn relay? I'm suspecting that when the ignition goes ON the horn relay is shunting current thru the fuse to ground, burning out the fuse. But I can't even figure out where the horn relay is! I think it's under the dash up above and behind the fuse bax (not under the hood), but can't find a map anywhere showing me which one it is. Can you tell me where it is? Also, I'm not sure how to check it out when I find it.
Also, as I've looked around for help on this, I keep reading on the web about "clockspring" problems. Is this related? (I don't even know what the "clockspring" is!)
I appreciate any help you might be able to give me!
Thx,
Joe
Answer -
Hi Joe,
Unfortunately I don't have the actual wiring diagram for the horn system on the van but I do have some information from the Haynes van manual. It says that there are two fuses in the horn system: fuse #6 in the power distribution center (a box under the hood near the battery) and fuse #7 in the junction block (fuse and relay panel under the dash). Can you tell me which of these two fuses is blowing and the amperage rating of those two fuses? I believe that the fuse #6 is the one that supplies high current to the horns necessary to power them, and that current is conrolled by the switch function of the horn relay. I believe that fuse #7 provides power to the switch actuation function of the horn relays and uses low current that is generated when the horn button on the steering wheel is pushed and that grounds the far end of the actuation coil of the relay. That coil is connected to the hurn button by the clockspring wire that you asked about which is located between the steering wheel and the steering column. That clock spring wire can break and thus prevent the operation of the horns if the wire just 'floats', but if it breaks and as the result is grounded, the effect would be that the horn would blow and refuse to stop blowing.
It is possible that one of the pins of the relay is shorted to ground internally either in the actuation section or the switch section, and which fuse blows would tell us which part of the relay were bad, or which part of the wiring to or from the relay were bad. The relay is described as being in the fuse block under the dash (along with fuse #7). Once you find it you can apply 12V from the battery between pins 85 and 86 (try both polarities) and see if it will click (caution, just touch the second lead in case it is shorted internally so you don't get a burn from the overheated wires). If it clicks, then test the continuity between 30 and 87 with your ohmmmeter. If it both clicks and has continuity then the relay is o.k.
So let me know about which fuse is blowing, please. I suspect that you have a wire shorted between the fuse and the relay or the relay and the horns but which wire depends upon which fuse is blowing and under what circumstances.
Thanks for giving me the results of your measurements which are helpful.
Roland
Roland,
Thanks for your reply. Sorry it's taken me so long to respond back to you.
I have a Haynes Automotive Repair Manual and basic T&C Owner's Manual. Both of them tell me that there's a "horn fuse" in slot #7 in the junction block (beneath the steering wheel) -- and I can find it. That's the 20-amp one that keeps burning out.
The Haynes manual also says (ch 12, 21-1)that there's a "horn fuse" in slot 6 of the Power Distribution Center (PDC) (which I take to be the "Fuse and Relay Center" next to the battery). But that fuse #6 there is actually the Lower Left Headlamp (15 amp), and it is perfectly fine (not blown). I can find nothing else in either the PDC or Junction block identified as horn-related.
Re the horn relay, there are a bunch of relays in both the junction block and the PDC, but I can't find anything identifying which is for the horn (even though the Haynes manual says that it is "located on the Junction Block" 12, 21-3). I looked thru the many pages of wiring diagrams at the end of ch. 12 of the Haynes book and couldn't even find the horn circuit! How do I find the horn relay? I don't like the idea of just pulling every relay I can find and trying to find one that doesn't seem to work OK -- I fear I'll end up breaking something. Is there a way to actually identify which relay is the suspect one?
I did decide to try an experiment: I replaced the burnt 20-amp fuse #7 in the junction block with a new (sacrificial) one. Without the ignition key OFF, the horn worked fine. Then I turned it ON. The fuse immediately blew and the horn wouldn't work. This is exactly the same as I wrote in my first message.
And what about that second horn fuse located in the PDC? It's not #6, unless it's doing double-duty with the headlamp! Does it actually exist?
Re the "clockspring", your earlier message said that if it's broken and floats then the horn wouldn't work at all, but that if it's grounded the horn would blow continually. In this case it worked briefly until the ignition went ON. This makes me think that the clockspring is OK. Would you agree?
Can you help me find the relay to run the check on? Or the PDC fuse? Or any other solution? Thanks for your help!
Joe
Answer -
Hi Joe,
Unfortunately at this point I don't have any wiring diagrams other than the same Haynes that you have. I may be able to get a Chrysler manual soon with complete diagrams. I suspect that there is nothing wrong with a fuse in the Power Distribution Center, so I wouldn't worry about that. As for the relay, I would just try the horn, with the ignition off, after pulling each of the relays under the dash until you pull one that kills the horn. I suspect it may be bad, but I am not sure how turning on the ignition would blow a fuse when you try the horn (without a circuit diagram). I will let you know when I get a full set of diagrams.
Roland
2/13/06
Hi Roland,
I bought a replacement relay and went in search of the offending horn relay this afternoon. Failure. But I now have a different failure mode.
I've had no fuse in the horn-fuse slot (#7) for some time now. Every time the ignition is ON, the fuse burns out. As I mentioned earlier, in the past I've measured 10Kohms from the top of the fuse-slot to ground with the ignition OFF and zero ohms with the ignition ON. Today, though, I measured zero ohms whether the ignition was OFF or ON.
Then I tried to locate the horn relay. Working in groups of 3 or 4 relays, I disconnected the battery ground, then pulled out every relay in both the junction box (behind the dash beneath the steering wheel) and the Power Distribution Center (beside the battery under the hood), then reconnected the ground. There was no change in the resistance measurements. Finally I had all of the relays out with the ground connected: zero ohms from the top of the relay to ground.
Then I disconnected the battery ground again.
Then I inserted a new good fuse into slot #7.
Then I reconnected the battery ground. The horn immediately sounded, even though the ignition was OFF and the relays were all out. I disconnected the battery ground. The fuse had not burnt out.
I started putting in relays in groups of 4 or so, hoping to isolate one that would change the honking pattern. In each case I briefly reconnected the ground to the battery and in each case the horn honked. Finally I had all relays back in place. I pulled the fuse, reconnected the battery ground and re-inserted the fuse. With the ignition OFF, the horn honked steadily. I pulled the fuse out. That's where it stands now.
I never inserted the new replacement fuse at all.
I'm hopeful that maybe I somehow disturbed the bad relay and it toggled into a “horn-on” position, but I really don't know.
One other point: the relays in the junction box (under the steering column) are not easily accessible. I can't see them very easily as I reach in for them.
Any ideas?
AnswerHi Joe,
My suspicion is that you have a short circuit that involves 2 or more of the the three wires at the horn relay socket in the juntion block. So you will have to go to the dealer parts department and ask them to pull up a picture of the junction block and locate the position of the horn relay in the block. Then you will need to unmount the junction block so that you can get to the rear side of it and inspect the wire connections and also look for any breaks in the insulation of the wires going to that socket. The three wires are:
a wire from fuse #7 (red/yellow?)
a wire that goes to the clock spring (black/red?)
a wire that goes to the horns (dark green/red?)
The colors are based on my '93 shop manual color assignments for the relay which I hope are not changed.
The lead from the fuse is probably either touching the lead to the horns (thus by-passing the relay function) or alternatively it is touching a ground point (which shorts out the fuse). I don't have a good explanation for the role of the ignition switch in the scenario in the past, but it may depend upon where the short to ground is located. It may be a ground that is established by the action of the ignition switch.
Once you get to the back side of the horn relay socket where the wires are attached I believe it will be clear.
Another approach would be to make measurements of the 3 pins in the base of the horn relay socket, which will no doubt verify the shorting out theory, but even then you will need to demount the junction block to to see what is going on with the wires that are hidden from view.
Roland
