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Quick bypass switch for stock aux. electric fan
- Thread starter YELLAHEEP
- Start date
There's your problem. In order for the "just unlug the compressor and put your AC on in the Jeep" trick to work your AC system must be properly charged with freon. '97 and later (maybe even everything after '91 I didn't look) has a low and high pressure switch in the AC lines so that the compressor will not run if the system is either over or under charged. If it does not sense that the system charge is correct it will not cycle the compressor and therefore not turn on the cooling fan.
If you would like this to work you have four choices.
1) Fix your AC system. I know that's very unlikely
2) Put a switch on the dash and activate a relay that bypasses (actually jusps the contacts)the fan relay in the fuse box. Switch on, fan runs all the time. Switch off, fan system works with the ECU as normal.
3) Run a wire to the PCM to fake the system into thinking the AC system is charged normally. From my diagrams it looks like it should be the Blue with white wire going into the PCU (wire 22 of connector 3). It should be grounded. Then the fan will run any time you turn on the AC. Disconnect the AC clutch wiring as suggested because you don't want the compressor running with no freon in the system.
4) Find the AC pressure switches in the system and install a jumer in their place. Will work as described in 3.
HTH,
B
If you would like this to work you have four choices.
1) Fix your AC system. I know that's very unlikely
2) Put a switch on the dash and activate a relay that bypasses (actually jusps the contacts)the fan relay in the fuse box. Switch on, fan runs all the time. Switch off, fan system works with the ECU as normal.
3) Run a wire to the PCM to fake the system into thinking the AC system is charged normally. From my diagrams it looks like it should be the Blue with white wire going into the PCU (wire 22 of connector 3). It should be grounded. Then the fan will run any time you turn on the AC. Disconnect the AC clutch wiring as suggested because you don't want the compressor running with no freon in the system.
4) Find the AC pressure switches in the system and install a jumer in their place. Will work as described in 3.
HTH,
B
Well, how handy are you with electrical? Let me know and I'll lay out a proceedure based on your ability.
Basically though you'll be installing a suitably sized relay to run the fan. You'll connect the swtich to hot (best if this is only hot when the key is on) on one side and to the coil of the relay on the other. Then one contact of the relay will go to battery hot (fuse this at 40A) and then to the light blue wire running to the fan. You tap into the blue wire but do not cut it. This way your fan will still run with the computer as normal but will run all the time with your switch turned on. You should also not get any check engine lights this way.
If you need more details let me know.
B
Basically though you'll be installing a suitably sized relay to run the fan. You'll connect the swtich to hot (best if this is only hot when the key is on) on one side and to the coil of the relay on the other. Then one contact of the relay will go to battery hot (fuse this at 40A) and then to the light blue wire running to the fan. You tap into the blue wire but do not cut it. This way your fan will still run with the computer as normal but will run all the time with your switch turned on. You should also not get any check engine lights this way.
If you need more details let me know.
B
- Location
- East of Cincinnati
Bloose said:
It was easier for me to use the relay already feeding the fan, and just run my switched hot to that coil.
So rather than have two relays running the same fan, I have two switches running the same relay.
The case where your setup is better is when the stock relay fails. You'd have an independent backup. I don't...
Robert
This is a little O/T but you guys might know the answer to my NSS question.
I was wondering if i could short both the B-C to get it in Neutral/Park (to start) and A-E through a switch on my dashboard (for reverse lights) at the same time? Or would this confuse the computer and cause damage by having two seperate things "activated"/shorted at the same time. Thanks in advance.
I was wondering if i could short both the B-C to get it in Neutral/Park (to start) and A-E through a switch on my dashboard (for reverse lights) at the same time? Or would this confuse the computer and cause damage by having two seperate things "activated"/shorted at the same time. Thanks in advance.