ok which inline fuse is it. I looked and there is four there is two right by the console blue, and a white on and two closer to the firewall area and i beleive there was white with blue stipr and red. and what is the best way to check these before i mess something up. in my hot rod days i would just take them out but dont wanna do that to this car

 

i dont know the name of those but they dont have a fuse its just a gray plastic unopenable thing on the wires

 

There are fuses all over the place on these cars. Specifically check BOTH fuseboxes (I do think there was one in the driver's side labeled heater control) as well as two inline fuses - one inline directly on the amplifier ground wire (driver's side cheek panel) and another inline on the passenger's side up alongside the pushrods for the flaps. I'm not real sure what this particular fuse does I just know it's there and it's a surprising pain to get apart and check the condition of the fuse inside.

Not sure what you mean by "power and ground opposite each time" but unless you followed my instructions to the letter you're either on the wrong end of the connector (you did separate the two halves, right?) or you're crossing something up to ground out the 12v. If you aren't clear, stop and ask for clarification. I think we're all 90% certain your amp is bad, but if you are not 100% positive what voltage you have on what wire (get a new meter before proceeding) and WHERE YOU NEED TO SEND THAT VOLTAGE TO, you run the risk of burning up what might have been a good amplifier ($250) or a good servo ($650).

 

You want the one on brown and brown/yellow wires


Cheers
DD

 

power and grpound opposite ment when I hook power up to the red and ground to purple and vise versa. I did separate the two half. I got another meter and im not showing any power to either.
Do I hook up a power to the purple and ground elsewhere or to the red or vice versa

 

With the meter, you should be checking for 12v on the side of the connector that seems to loop back towards the firewall (this is the feed coming from your amp). The other half of that plug, closer to the front edge of the console, is the feed into the servo. You won't see any power there at all with a meter. You're checking on the correct halves of the plug, right?

Did you check your fuses? Found any of the ones we mentioned blown?

Now, using jumper wires (and AVOIDING touching any OTHER pins inside the connector), send 12v to the PURPLE wire on the SERVO half of that connector (while disconnected). GROUND the red wire. Hear the motor whir? Pushrods move?

Now send 12v to RED and ground out the PURPLE. Should move back the opposite way.

Make sure you're not applying power to the wrong half of the connector, that's when you'll blow a fuse or fry the amp. Again just to make sure I'm 100% clear you're CHECKING for voltage with your meter at the half that loops behind the AC unit towards the firewall...and you're APPLYING voltage to the half by the front edge of the console.

And you do have the key on and the AC control in auto, right?

For what it's worth if you can get the servo to move, I believe 12v to purple and red to ground will give you heat on all the time if you leave the connector unplugged, just be careful not to overtravel. This will force heat on until you can replace the amp (if we conclusively decide that's what it is).

D

 

i actually checked for power on both ends of the connector and didnt find any. i put power to the end that goes into the front of the console the one with female plugs and didnt see anything happening. maybe im doing something wrong here i usually have the car running and the heater on auto do i need to move it to a/c??

 

Even if the amp is functional there won't be power on either of the wires if the system thinks the servo does not need to be driven.

Turn the temp control knob to full heat or full cold. If the amp 1) recognizes the request and 2) is operational, will you have voltage on the purple or red wire





Try this.

Unplug the amp. Now remove the right side cheek panel to locate the red and purple wires where you can actually SEE them go into the servo motor. Cut away a small bit of insulation on each to reveal the wire strands. Now try applying power and ground again.




To drive the servo by directly applying power and ground does not require the key to be "on".

To *check* the red/purple wire voltage the system must be on *and* in a status where it *should* be adjusting itself, as mentioned above. In other words it must be repsonding to a temp change request.

The "auto" setting is fine for this.

Your remark "...move it to a/c?" is confusing. There is no capability to do that. The mode switch should have "off-lo-auto-high-def" settings only. Do you have something different?

Cheers
DD

 

no i have a slider switch under all the controls on the console that when pushed to driver side says air or a/c i dont remember and when pushed to driver side says heat i beleive

 

unplug the amp?? is that the 18 slot plug and then remove the cheek panel on passenger side is the servo motor behind the console or behind the cheek panel?? All I can see is wires going round the back and going behind the console which way do I need to go here I love my car and dont wanna mess anything up on it.

And by the way thanks Doug you have helped me alot on my car we go to Longview quite often might have to buy you lunch sometime. Are you a member of the portland jag club

 

John,
By separating the two halves of the 18-pin connector you are unplugging the amp. There is another 18-pin connector identical to the one you've been working on under the driver's side cheek panel. This is directly attached to the amp itself.

I am bothered by the fact that you have no power - while possible I think this still points to a blown fuse. Pull all the fuses related to the AC system and check them - not visually, but check them for resistance with a meter. It's possible for a fuse to LOOK ok but not BE ok. Check the inline fuse on the amplifier ground wire (driver's cheek panel), the one on the brown/yellow wire you found earlier, and anything in the fuseboxes.

After checking all the fuses and putting them back, repeat all of the above tests (check for power red/purple, apply power) with the control knob in auto and repeat each test with the temp knob in full cold, full heat and somewhere in between.

If you have no power to red/purple, where are you drawing 12v from in order to send power to red and purple? I find it hard to believe you have both no power to the system (or coming from the amp) AND no movement from the servo when you send power to it.

D

 

Forget about that for the time being. That merely changes the upper versus lower temp bias when the system has stabilzed in blend mode.

Cheers
DD

 

Indeed.

It might be useful to check for power on the *brown* wire to the amp. This is the voltage *supply*.

To clarify, it would not be normal for either the red or the purple wire to always have power. If the amp sees no reason to drive the servo then those wires both go neutral or ground...can't remember right at the moment.




Some "known good" voltage supply, hopefully :-)






Yeah....It does seem odd....but that's the name of the game with old XJSs :-)

Cheers
DD

 

John, has the subject of the water temp switch on the heater core inlet tube come up? I can't remember.

Bypass the switch by removing the wires and jumping them together. Report back if anything changes.

If this switch is stuck open the system will not work at all in heat mode.

Cheers
DD