Constant Voltage at Clock Fuse Y/N ?

[AnotherOldJeepGuy]

Got in the jeep this morning, no radio.  All black so is not powering up.  Before pulling the dash trim and radio unit I checked the fuses.  The Radio Fuse is good.  With the key off, voltage there is 0.  With key on it is ~12V.  It's worth noting that my ACC position has not worked for years since a shop replaced the ignition switch, which I didn't catch until long after the repair was done.  Anyway....

 

I also checked voltage at the Clock Fuse because even though I don't have a clock, I took a guess that since a clock would require constant power, that this clock fuse might also control the radio constant power.  Does it?. 

 

What I see is the voltage at the Clock Fuse is also 0 when the key is off, and ~12V with the key is on.  Is the voltage at this fuse supposed to be switched or constant?

 

I'll be pulling the radio unit Saturday morning (when it's not yet 100 degrees out there) so that I can probe the voltage where it really counts for powering up the radio, but I may ultimately be back at the questions above, so might as well ask them now.

[87MJTIM]

The clock fuse is only hot in run.  The fuse that is hot at all times for the clock is the ETR.

 

 

I would suggest you check the grounds for the radio.  Cruiser was always harping on grounds.  My experience was with the clock.  It would sometimes display or display very dimly.  I did Cruiser's instrument panel ground upgrade and the clock displays bright now.

 

To quote the Beach Boys:

 

       "Ground, ground, get a ground, i need a ground." (or something like that.)

[AnotherOldJeepGuy]

Thanks.  I didn't know the Beach Boys has such automotive savvy!  Perhaps they acquired that expertise working on the little deuce coupe.

 

Interesting that the Clock fuse is not hot all the "time", but now I know!  I'll check the ETR fuse, and look into the panel ground upgrade info.

[AnotherOldJeepGuy]

Hmm, I don't have an ETR Fuse!  There are no contacts for it at the bottom end  (circled) and there is no "ETR" printed on the assembly as other labels are.  I also don't have the 30A that is shown next to it in this scan from my owner's manual, not that that's related to this problem, just noting it doesn't exist either.  Since the radios I have installed over the years, including the current one have all worked since 1990 until yesterday, and I don't see 2 fuses laying on the floor, it's pretty reasonable to assume these have never been there on my particular vehicle.  So whatever my issue is, it doesn't appear to be a blown ETR fuse in my case.  Perhaps this, and the 30A, exist for some other MJ variant?

 

 

[watchamakalit]

"I got a ground wooo ooow. I got a ground."