View Full Version : Hole in Firewall???

04-21-2003, 07:44 AM
Hey guys,

I need to find a hole in the firewall of my '89. Can't seem to find one so I'm hoping someone here knows where one is. I would prefer it to be on the driver's side of the car, but it doesn't have to be. It must be big enough to run 3 10-guage wires through. Thanks for all your help,


04-21-2003, 01:10 PM
I assume you're going to be hooking some speakers. There is a hole where some electrical stuff goes through on the driver's side but i would NOT advise to use that. Even though it could be fine, those sub wires may heat up possibly and just mess with the electrical things. As far as i know there's really no other hole you could use, it's better to be safe to just make another hole, and that's what i would say to do so you know it's only those sub wires going through it. It's a pain to get in there to that fire wall, a shop could do it for cheap, if you just told them you wanted that one hole, im sure some place would do it. good luck--
by the way, i have subs also with one 8 guage wire, and i took mine to get installed and they made a separate hole near where the electrical wires go through.

04-21-2003, 02:52 PM
Actually I am going to run 3 wires through to control the fan. My problem is this: When I bought my '89 a few weeks ago, the fan didn't run at all. I have replaced the IRCM once with one from a junkyard, but that didn't solve the problem. I don't believe the fan is bad because when i hook it up to power and ground it works (but it runs high-speed all the time). Since I don't feel like shelling out the money for a brand new IRCM I figured I would just hook the fan up to a dimmer switch that I can mount in the car and control the speed of the fan with. I need a hole in the firewall to run the three 10-guage wires through. However, if anyone wants to offer some insight as to what is wrong with my fan, maybe I could fix it the way it is supposed to be and not have to worry about the switch.



04-21-2003, 06:34 PM
Matt, If you dont feel like going to a shop to drill a hole, you can punch a hole as high as possible in the steering boot. You should be very carefull not to let the wires get too close to the steering shaft. If the wires get wrapped around the shaft, you will be in deep *****. Just zip tie them up and away. I did this with a 4 guage and have no problems. I dont know whats wrong with your fan but i dont recomend a dimmer switch. Unless the switch can handle high amps. A normal switch will burn out in a few months at most. Hopefully someone else can give you a little more advice. Good Luck

04-21-2003, 11:14 PM
Yes, like an idiot I ran 14-guage wires throught the doorjam with a 20-amp toggle switch from wal-mart. That lasted about an hour before it blew the switch completely. That is why I want to run 10-guage (that's what FORD used for everything else) with at least a 30-amp dimmer. I would really like to be able to fix the fan so that it works the right way, but I don't know if that's going to be possible. I was sent a wiring diagram a while back with a way to hook it up but I couldn't understand it one bit. My friend who knows more about SCs than anyone I've ever met couldn't figure it out either. If anyone has any suggestions PLEASE let me know, I really don't feel like flipping the fan on and off every time I enter and exit the car; but I'll do it if I must. Thanks for everyone's help,


04-22-2003, 04:16 AM
There isn't a secondary hole that I know of. Its easiest just to drill a hole beside the main wire connector on the driverside. Then run your wires and seal it with silicon sealant. You can drill the hole yourself; its not hard and you won't need a large hole for those few wires.

04-22-2003, 04:43 AM
sounds dangerous, I would wire two 30 amp relays in parrallel (60 amps) to the switch inside. This way you can just run one wire(ground wire) to the switch, and toggling the switch will ground one side of the relay making the contact complete, only need maybe an 18 gauge wire this way

04-22-2003, 09:57 AM
Yep, what he said.


04-22-2003, 12:03 PM
Thanks Assclown, I think I'm gonna try that - I'll let you know how it goes.

Hey Tubeamp, how did it go with the tint removal? I remember seeing your post and I think you may have been in my post as well. Get it all off?

04-22-2003, 02:27 PM
Awwhhh man, the weather has been really strange here in Toronto...rains one day...snow the next (for a few days), then mid to high 70's one day...rain and ice storm the next. So basically...no. But thanks for asking:D


04-23-2003, 03:30 AM
Does your fan run when the AC is turned on? If it does then the problem might be with the coolant temp sender for the EEC (not the gauge). How do you know that the fan does not work?


04-23-2003, 08:00 AM
No, the fan doesn't run when the AC is turned on. I know the fan doesn't work because it doesn't run ever, and if I try to drive the can the temp heads straight for the roof. When I had the toggle switch hooked up (before it blew), I could turn the fan on and the car would cool back down.


04-23-2003, 07:31 PM
Ok then here is an easy way to hook up a relay. Use a standard ISO relay. It will have 5 pins.

85 connect to switch. connect other side of switch to ground
86 connect to 87
87 connect to +12V fused at 30 amps
87a N/C
30 Connect to fan LOW SPEED only

Only 3 connections. The wire for 85 and 86 can be as small as 24 gauge, or as large as you like. Use 10 gauge for 87 and 30.


04-24-2003, 10:30 PM
Alright let me run something by all of you. Do you think it's possible that my thermostat is just bad? Maybe it just plain doesn't work, so it never turns the fan on. If this is a possibility then I'm going to replace it and hook up the IRCM the way it was supposed to be and see if that works. Please let me know if this sounds plausible.

Thanks, Matt

04-25-2003, 12:49 AM
No because when you turn the AC on it turns the fan on regardless of tempurature. Since your fan doesn't come on when you turn the AC on then that would mean that:

1. the relay coil is bad.

2. the contacts for that relay are bad.

3. there is no power going to the relay contact.

Maybe both modules are bad. Maybe you have a blown fusible link. If you disconnect the temp sender to the EEC the high speed fan should come on. This is the sensor with 2 wires instaed of one at the thermostat outlet.


04-25-2003, 01:19 AM
i have the same prob, but from what i've come up with is, the IRCM, pin #14, cut it, it runs the low speed....there's a guy on here that cut his 3 years ago and everything is fine...

04-25-2003, 01:40 AM
Well do what you want. Tie some bailing wire on the bumper cover to hold it up. There are a few things I think you guys are missing.

These cars, probably have more than 100K miles on them. In that 100K most probably have the exact fan motor that they rolled off of the assembly line with. That motor has been operating at temps of over 100 degrees for at least 8 years (assuming a 95). Every mechanical part has a finite life, and just running it the way the factory intended shortens the motors life. What do you think running the motor continously does for it's life? Motor life is derated for temperature meaning that as temp goes up life goes down. They are also rated for a operational life in hours.

The other thing is that is left out when guys overheat all the time is that they immediatly want to add a cool fan switch or something. Well it ran fine B4 what changed? Why would you have to run the fan all the time? Well it's because something else is the problem, whether it is an airpocket in the system or the pieces that help channel through the rad core are remove or otherwise inoperable or the bumper cover has come loose from the bottom of the car and air is escaping under the car instead of through the core, you need to correct the problem and not mask it. I know it's not the question here but it is related.


04-25-2003, 10:12 AM
Hey all, couldn't help but notice this thread...have to put my 2 cents in if you would. Personally I have done this mod...I used a switch on Pin 14, works great. I can control the fan motor at anytime. Best thing about it, fan doesn't run everytime the car is running...I drive the car in the winter.

Also have to agree with J57ltr, undo stress and heat on an old electical motor is not the best for it. Though, you could look at it in a different school of thought, no stress of start and stop times..burns armature and contacts etc....

I prefer to control on/off (hey I got to be me)