XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Aux fan circuit in 95 XJS

 
  #1  
Old 07-10-2019, 12:16 AM
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Default Aux fan circuit in 95 XJS

Gents;

i need some help with wiring, itís a little complicated, please bear with me.

In place of my auxiliary stock pusher fan, I have two SPAL pushers in front of the condenser. One 11 inch more powerful one, and another one, 9 inch, pancake type, and not quite so strong. Together they pull 30 amps

I am running ONE SINGLE SPAL fan relay (up to 40 amps, allegedly) for both. I am using stock wiring to power the relay and have replaced the stock fuse to 30amp. Everything has been working well.

However, I have now introduced a lower temp radiator switch, which is making the fans run more often and after shut down. Which I find desirable.

I have noticed that my relay is getting a little warm, as is the wire that powers the fans from said relay.

I called the dealer that sold me the fans, and they recommended I run each fan on a separate relay. I have now ordered another SPAL relay kit.

Now i would like to add another fuse to the aux fan circuit, preferably in one of the empty spaces in the fuse box (there are two, I believe) to power the incoming relay. All the wiring is really obvious to me, except this point. My electrical diagram is not helping me at this point.

Any help appreciated

EDIT:

and just to give a visual aid, these are my pusher fans working after shut down. You can see the Spal relay some of the wiring, and I tried to get a clear shot of both fans, but no such luck. Yes, they are loud and effective

 

Last edited by Spikepaga; 07-10-2019 at 12:49 AM.
  #2  
Old 07-10-2019, 12:37 AM
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Ok I think I sort of pulled myself together right after that big write-up



The battery powers the fuse directly on the circled wire with the arrow pointed at it. That currently has a 30A fuse and is powering the relay which in turn is powering both fans.

The question is if I can get power from this very same wire to another fuse to power the new relay.

Remember that no additional fans are going in. I am simply adding a new relay. No additional power drain. It already looks like this wire feeds other items higher up on the diagram. I would just be splicing another wire to get my battery power to my new fuse and relay.

Thanks for anyone patient enough to help me
figure this out.
 

Last edited by Spikepaga; 07-10-2019 at 12:45 AM.
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Old 07-10-2019, 06:20 PM
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So I already started taking things apart to prepare to install the additional relay :

The 30 amp fuse is on stock fusing and gives power to the SPAL relay powering the two fans, which it has been doing for years



Flipping this over, The brown cable is battery power, I want to split that battery cable to another fuse for the new relay. This should be ok, right?


 
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Old 07-10-2019, 09:06 PM
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A word of caution; the fuses are there to protect the wires, nothing else. That 15 amp fuse holder matches the wires going to it. If you double the load and double the fuse rating, you should be doubling the wire size, or add a separate wire for the second relay and fan. The relay's control circuit themselves won't draw much but the large amperage passing through them when energized will and will need a separate wire feed to the fans.
 
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Old 07-11-2019, 12:47 AM
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Originally Posted by carsnplanes View Post
A word of caution; the fuses are there to protect the wires, nothing else. That 15 amp fuse holder matches the wires going to it. If you double the load and double the fuse rating, you should be doubling the wire size, or add a separate wire for the second relay and fan. The relay's control circuit themselves won't draw much but the large amperage passing through them when energized will and will need a separate wire feed to the fans.
The fuse rating has been doubled for years with no ill effect. I inspected them today. The feed cables to the fans are coming directly from the aftermarket SPAL relay.

What I would basically be doing is splicing into the battery cable pointed to in red and creating another fuse for the new relay. I suppose I could just the wire directly from a battery point in the engine bay if I have to. Not sure where though...


 
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Old 07-11-2019, 05:21 AM
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Ok, I see what you're saying. The original fan drew 15amps where you show the original fuse. The original fan used the one wire coming from the LF3R bulkhead post that is hot batt connected(always hot. The fan and original relay were fed by the same wire (see snip of original) going to fuse 4 of left front fuse panel, then going to 52 where it splits, shares same wire for control and main power.



You are now asking that same wire to feed a new set of fans that draw twice as much by simply adding or splicing in a 2nd wire and fuse off of the same original wire before the fuse box.
My suggestion is, while is it is ok to use the original feed wire and fuse to power the control to the new relays, the wire to actually power the fans, which the relays would be controlling, should come from a heavier feed cable. You could run it directly from the post on the firewall/bulkhead. (its near the heater valve on firewall) So the fuse for the control of the relays can remain using the original 15 amp fuse to 52, then add your new heavier wire from the bulkhead post through the new 30 amp fuse and out to the fan relay main contacts for actual power to the new fans.
Proposed new schematic:
 
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Old 07-11-2019, 11:38 AM
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Originally Posted by carsnplanes View Post
Ok, I see what you're saying. The original fan drew 15amps where you show the original fuse. The original fan used the one wire coming from the LF3R bulkhead post that is hot batt connected(always hot. The fan and original relay were fed by the same wire (see snip of original) going to fuse 4 of left front fuse panel, then going to 52 where it splits, shares same wire for control and main power.



You are now asking that same wire to feed a new set of fans that draw twice as much by simply adding or splicing in a 2nd wire and fuse off of the same original wire before the fuse box.
My suggestion is, while is it is ok to use the original feed wire and fuse to power the control to the new relays, the wire to actually power the fans, which the relays would be controlling, should come from a heavier feed cable. You could run it directly from the post on the firewall/bulkhead. (its near the heater valve on firewall) So the fuse for the control of the relays can remain using the original 15 amp fuse to 52, then add your new heavier wire from the bulkhead post through the new 30 amp fuse and out to the fan relay main contacts for actual power to the new fans.
Proposed new schematic:
thanks for taking the time to do this, I appreciate it.

I guess I will just use new wiring for one of the fans per your diagram...Only thing is they give you this loop with the fuse that is split and supposed to be connected to the battery post, but I want a cleaner look, so I guess running a regular auto parts store 10 gauge wire from the post to the area where all the other fuses are at should work....
 
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Old 07-11-2019, 04:29 PM
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Originally Posted by carsnplanes View Post
Ok, I see what you're saying. The original fan drew 15amps where you show the original fuse. The original fan used the one wire coming from the LF3R bulkhead post that is hot batt connected(always hot. The fan and original relay were fed by the same wire (see snip of original) going to fuse 4 of left front fuse panel, then going to 52 where it splits, shares same wire for control and main power.



You are now asking that same wire to feed a new set of fans that draw twice as much by simply adding or splicing in a 2nd wire and fuse off of the same original wire before the fuse box.
My suggestion is, while is it is ok to use the original feed wire and fuse to power the control to the new relays, the wire to actually power the fans, which the relays would be controlling, should come from a heavier feed cable. You could run it directly from the post on the firewall/bulkhead. (its near the heater valve on firewall) So the fuse for the control of the relays can remain using the original 15 amp fuse to 52, then add your new heavier wire from the bulkhead post through the new 30 amp fuse and out to the fan relay main contacts for actual power to the new fans.
Proposed new schematic:
Wow, looks like I just made a tragedy out of something extremely simple....

carsnplanes, if you could bear with me a little longer, I just have 3 basic questions

1- I have some run of the mill 10 gauge from the auto parts store lying around. Can I use it to connect to the positive port? The fan relay kit will come with something like this and they expect you to cut it and crimp a connector on one end and hook it up to the + terminal, and the other end to the fan relay power wire but I want the fuse to be closer to the other fuses. For aesthetic reasons....so can I just make this longer with the 10 gauge I already have ?



2- currently both fans are grounded to the OEM cable,
soldered. I am assuming this can remain as is?

3- is this the positive port I can use immediately right of the water heater entry on the firewall?


thanks so much for all your help

 
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Old 07-11-2019, 04:50 PM
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1.Yes, 10 Ga should be plenty and the fuses can be near the other fuses. The longer the run, the larger the wire. Does your 10 look larger than the original?
2. I would try to fit new grounds directly to chassis with 10 Ga wire as well. I don't know the Ga of the original wire and if your adding amperage to the main feed wire of 10Ga, then you should be doing the same for the grounds. It's the same circuit and all wires will feel the same current draw.
3. Yep, that should be the Hot Bat post LF3R
 
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Old 07-12-2019, 08:03 AM
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Originally Posted by carsnplanes View Post
1.Yes, 10 Ga should be plenty and the fuses can be near the other fuses. The longer the run, the larger the wire. Does your 10 look larger than the original?
2. I would try to fit new grounds directly to chassis with 10 Ga wire as well. I don't know the Ga of the original wire and if your adding amperage to the main feed wire of 10Ga, then you should be doing the same for the grounds. It's the same circuit and all wires will feel the same current draw.
3. Yep, that should be the Hot Bat post LF3R
Thank you- I should be getting the second relay today. This should be very simple to do, thank to your advice.
 
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Old 07-13-2019, 05:33 PM
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Thank you again it all worked out well. Took me longer than expected. I think the fans i
are blowing a lot more air now that each is running on its own relay. I tested and tested and left them running for 10 minute increments, did not hot wires, or hot relays, just warm, which is normal.
 
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Old 07-13-2019, 08:36 PM
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Originally Posted by Spikepaga View Post



Thank you again it all worked out well. Took me longer than expected. I think the fans i
are blowing a lot more air now that each is running on its own relay. I tested and tested and left them running for 10 minute increments, did not hot wires, or hot relays, just warm, which is normal.
That's great it all worked out. Make it all nice and pretty by snipping the tails off of the tywraps .
 
 
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