Trouble Shooting A/C Fan that won't turn off '97 DB-7
 

I'm new to this forum and signed up for some troubleshooting help. I don't really see anything like that here am I on the wrong forum for that kind of thing?

What is the issue you're dealing with?

You will not find much of anything for DB7 support here. Maybe try Piston Heads forum? DB7 has 2 blower motor assemblies which need to be removed to service relays or replacement of the Transistor that controls the low/medium speeds.

Isn’t that similar to the jaguar XJS? You might want to ask on the jag lovers list.

Certain MY Jaguar parts do interchange. Finding a good ones can be difficult.

True
But the XJS guys might be able to point you to someone that rebuilds these parts. Also the troubleshooting should be similar. (I used to own an XJS)
Good luck

The A/C system on the DB-7 has 2 fan motors. One runs continuously when the key is on for circulation the other is speed adjustable. The constant run fan will now not turn off when the ignition key is in the off position. I pull the fuse so it does not kill the battery but it should not be getting power. My "guess" is that there is a relay somewhere that supplies it power but I have been thru the manual several times and can't find one. Any thoughts on what the cause is or where to look for the relay if there is one?
Thanks to everyone for your replies, I'll also check piston heads.

You might have a bad diode. I had issues with the blower motors on by departed XJS. Diagnosis was a bad diode. I could never find it.

That is possible, seems to me I read the fans had some internal circuitry.

Not sure where you got that information from, both motors run at 3 speeds depending on manual or auto operation. As I said before, you need to remove said motor with the fault to service components. There is a relay inside of the motor for high speed. If you have issues with low and medium, replacement of the transistor is needed.

Tampa DB7
Posted this on the XJS list and got a couple of replies. I have summarized them below.1) If the fan is the same, either the internal relay or the electronic board is creating a short
Does the DB7 have a fan speed selector, and does it make any change to either fan ?
Note : the relay is inside the fan case.

2) Search the Jag-Lovers archives for “Darlington Relay” or “Darlington transistor” and I think you will find what you are looking for. I have not had this problem, but I think others have and posted about it. I believe that “Darlington” component is located inside the fan motor housing as mentioned but the archives will have more helpful information.



3) Kirby is a well-known XJS contributor. He has also written a very detailed book culled from his and list member’s experiences and solutions. See the link below for a detailed understanding of the blowers and their controls.

Air conditioning blower control

Good Luck

Thank you embdenb
The fan speed has no effect when the key is off, one fan continues to run. With the key in the on position at least one fan goes to speed 2 then to high speed as selected. I cannot tell if the fan in question speeds up or not with the key in the on position.
But thanks this helps explain why the fan keeps running if the relay in internal to the fan.
Now all I have to do is find the fan.......

If the fan and housing come out the same method as the XJS then the following website might help. It's for an earlier XJS (1978) with a different wiring methodology. However, the blower motor and its housing are identical to the 97. It might help in getting the fan and housing out to inspect the electronics in the fan housing if that is what you want. (about quarter way down the website)

https://bernardembden.com/xjs/hvacmodule/index.htm

Here is a picture of the transistor inside of the blower housing. I have this LH blower assembly that is in good condition and works if interested.
-JW