Progress has been slow as it's been cold and ugly up here in Pittsburgh, but finally got the car in the garage, alongside the Jensen-Healey. So now I can at least work on it out of the elements. Tackling the horn and it's got me confused. I did a search of the forum but didn't really find a thread with a similar issue.

Using the schematics I know that the horn relay closes when either the horn switch on the wheel is pressed, or if the security module grounds it. I disconnected the steering wheel connector and I still had a resistance reading of around 2500 ohms. So I went into the trunk and pulled the security module (my battery is already disconnected). With the security module disconnected, I get an infinite reading on my multimeter and if I push the horn buttons you see the needle swing down towards 0 ohms. So the horn buttons are working as they should be. While I have the security ECU out I tested resistance across the horn sound pin and the ground pin, and there is my 2500 ohm reading. That shouldn't be reading anything, correct? That would mean that there is continuity to ground.

Could I just disconnect the "horn sound" pin from the security ecu? As far as I know there are no other issues with the security system (except it cycling the locks as the drivers door switch is bad).

 

Hi Michael,

I wouldn't cut the pin off of the Security ECU, but you could remove the terminal for the harness wire that connects to it from the electrical connector. Usually you can insert a small jeweler's screwdriver into the back or front of the connector and the terminal will release so it can be pulled out of the connector.

But first, have you inspected the horn relay to be sure its contacts haven't welded together in the closed position, or that corrosion hasn't bridged the load side terminals of the relay socket?

Cheers,

Don

 

Don, I should have worded it better, I didn't mean cut the pin off the ECU, but disconnect the wire to the pin. As for the horn relay I'm 99.9% positive it isn't the problem, as I've tried 3 different relays. It is quite interesting that the horn and wiper relays are the only connectors on the car with the old Lucas style round pins. I was almost wondering if there was a way to convert them to conventional relays, like the hella ones on the bulkhead.

 

Standard "ice cube" relay sockets with pigtail leads are available from most auto parts stores, so you probably could convert those relays to standard Hella/Bosch ice cubes.

 

I guess something in the security ECU is going bad. When I checked resistance for the pins on the lights, they all came back ok. So, I'll probably just disconnect the wire where it goes into the splice block under the left hand dash, it's easier to get ahold of and more room to work.