Radio/Blower wiring gremlin - JeepForum.com
 1Likes
  • 1 Post By CJ7-Tim
 
LinkBack Thread Tools
post #1 of 6 Old 08-01-2020, 10:33 AM Thread Starter
jeepburg
Registered User
 
Join Date: Mar 2018
Posts: 19
Radio/Blower wiring gremlin

Ok...I need some ideas here as Iím definitely out of them.

2000 XJ 4.0 completely stock.

Start the Jeep and have full power to both the constant and switched wires to the radio. Turn on the blower (doesnít matter setting or fan speed) and the switched power drops to almost zero. Constant power seems to stay ďconstantĒ (ie. no drop in voltage). Nothing else (lights/etc) seem to be affected. Turn the blower off and the voltage goes back to morning on the switched power to the radio. Since the constant isnít affected, itís of course retaining the time on the radio. When testing with the radio installed.

Side issue, my alternator seems to be over charging the battery (19-21V coming off the alternator). I thought that might be related but I disconnected the alternator and ran the battery down to 13V and still no change in the radio/blower issue. Iíll need to replace the alternator but that doesnít seem to be related to the this issue.

A couple other tests that I did were read the voltage at the battery with the blower on/off and no difference (no voltage drop when blower is on).

Iíve also tried the tests using a separate ground to the radio and no difference.

Also replaced the ignition switch with another used ignition switch I had laying around and no difference.

Iím hoping someone has some ingenious ideas because Iím completely out of them.

Thanks in advance!


Sent from my iPhone using Tapatalk

jeepburg is offline  
Sponsored Links
Advertisement
 
post #2 of 6 Old 08-01-2020, 03:13 PM
CJ7-Tim
Real Jeeps have dents
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis
Posts: 28,358
The first thing to suspect when the dashboard gauge indicates overcharging is loose, damaged, or corroded battery/alternator wires, or a faulty battery temperature sensor in the bottom of the battery tray. Clean/test/inspect/replace wires and connections. Have you tested and inspected the head unit wiring ?

Failure of the blower relay can happen. Visually inspect and test with your volts/ohms multi-meter from the dashboard fan switch to the fan motor. Look, smell, and test for melted wires. Inspect and test the blower motor resistor. Failure of the drivers door and the gate wire harness is very common, and leads to 12 volts positive shorted to ground or to the speaker wires. Test with your meter and visually inspect in the rubber boot for chafed insulation and damaged wires.

.
ďWhen the people find that they can vote themselves money, that will herald the end of the Republic.Ē

- Benjamin Franklin
CJ7-Tim is offline  
post #3 of 6 Old 08-01-2020, 08:29 PM Thread Starter
jeepburg
Registered User
 
Join Date: Mar 2018
Posts: 19
After doing a little reading, it doesnít seem like there should be any situation (regardless of the battery sensor) for the alternator to be sending 20V to the battery. What do you think?

Iíve checked the resistor with the multimeter and it looks ok. Also, Iím not sure I follow how a broken wire in the door can contribute to the problem when I have a multimeter testing the individual constant and switches wires in the radio harness. Can you explain that a bit more?


Sent from my iPhone using Tapatalk
jeepburg is offline  
 
post #4 of 6 Old 08-02-2020, 06:35 AM Thread Starter
jeepburg
Registered User
 
Join Date: Mar 2018
Posts: 19
One other oddity, the gauge on the battery dash is only showing 14V but my multimeter is showing 20V. Shouldnít the gauge be showing higher, or should I be throwing a code?


Sent from my iPhone using Tapatalk
jeepburg is offline  
post #5 of 6 Old 08-02-2020, 07:35 AM
CJ7-Tim
Real Jeeps have dents
 
CJ7-Tim's Avatar
2000 XJ Cherokee 
 
Join Date: Apr 2002
Location: out in the garage - Minneapolis
Posts: 28,358
18 years experience with 8 XJ Cherokees, most of which were fixer-uppers, tells me that if the dashboard gauge show 19 volts there is almost always a connectivity issue, such as loose wires or connections, corroded lugs or terminals, or internally corroded battery wires/cables.

The alternator has no voltage regulator and is controlled by the PCM, and the PCM uses data from the battery temp sensor. At the minimum, a physical inspection of the sensor, plug, and wires is required.

Both the tailgate and the doors have live 12 volts positive at all times. Failure of the wire harnesses is very common and leads to shorts to ground, which can enter any circuit, and easily cause 12 volt positive shorts to the speaker wires. At the minimum, a physical inspection of the wires is required.


What are the results of the blower motor wire circuit/switch/relay inspection ?
Saudade likes this.

.
ďWhen the people find that they can vote themselves money, that will herald the end of the Republic.Ē

- Benjamin Franklin
CJ7-Tim is offline  
post #6 of 6 Old 08-02-2020, 06:37 PM Thread Starter
jeepburg
Registered User
 
Join Date: Mar 2018
Posts: 19
Thanks Tim.

A visual inspection of all the blower wires hasnít turned up any broken wires (at least so far). I pulled the relay and tested it with a multimeter and everything tested ok (found the procedure online to test continuity/resistance).

As far as the voltage meter on the dash, it was reading 14v but I had 20V at both the battery and at the alternator (read via a multimeter).

One thing I did notice is I do NOT have continuity between the front left + speaker wire between the harness at the radio and the plug behind the kick panel (where the hood release is). Iíve traced that wire as much as I can see under the dash and I donít see any breaks...gonna have to dig around there a little more. I DO have continuity for the front left - wire from the radio harness and that plug. I also think the same wire is broken in the driver door boot. Once I pull the boot, Iíll fix that one too.

Your comment about a short from a speaker wire, wouldnít all of those speaker wires be ďdeadĒ if the harness is unplugged from the radio?

Also, do you know t he procedure to test the temp sensor? Iím assuming I can do a resistance test but I canít find what it should read. The service manual doesnít have any clues.

Thanks for all the help! Iím learning as I go here.


Sent from my iPhone using Tapatalk
jeepburg is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome