Jeep Enthusiast Forums banner
1 - 5 of 5 Posts

5 Posts
Discussion Starter · #1 ·
Hi new to this forum
Have a 2000 Jeep tj with A/C 4.0
Currently putting the hvac 5 relays for th
Fan and vac control switch
Now to my question…
I have a five relay set up like the one posted on this site can’t remember the user name my apologies .
However , he states to run a fused power to the vac switch and that runs in series with the fan switch through the Dark Green wire
the way I see it the DK Green wire supplies 12v to the 85 which is made when you turn the vac switch on to the fan switch
The 86 terminal is ground to the relay to complete the circuit .
The black ground is run through the 85 terminal to relay 5 then 87 runs to the harness upstream towards the power
Now for my dilemma
If I’m running power to the vac switch through the Dark Geeen wire
The first three positions cause continuity to the A/C input wire small green wire
When you get beyond the A/C modes in the vac switch the input green wire has no continuity which makes sense.
I get to this , to ask this
If I put power to the vac switch through the dark green wire (middle)
What do I do about the small green input for the air conditioner input wire
1-Does it carry 12v?
2-Is it a ground?
3-If it charges the 12 will nothing change.
4. Or do I run a 6th relay for the Input wire?
Looked all over the internet can’t seem to wrap my head around this.
Hopefully you can understand the gist
of my question.

4,668 Posts
The problem with following the various relay mods for this is that there are 2 completely different circuits depending on what year you have.

The ’97 & ’98 used 12v through the speed control circuit then in ’99 changed it to use the grounding circuit for speed control. Both relay mods use the same principal but must be wired differently.

Quite some time ago there was a long discussion on one of these forums where it started doing the mod & the method advised was from someone who had a ’97-’98. Then a long discussion when the guy tried it but happened to have a later year. It failed to work & all sorts of reasons were talked about back & forth as to why. Then at something like post 75 someone figured it out what was wrong. Even after that I think there was confusion.

If you understand electrical circuits including relay usage it is not too complicated if you also understand your particular blower circuit.

You are correct that the dark green wire at the mode selector in your 2000 is a grounding wire & so you would use a grounding wire to energize the relay through the speed switch/resistor & also a grounding wire for the terminal 30 connection.

The motor already gets its 12v from a relay & is constant whenever the key is on. From there the ground through the resistor controls its speed. Also of note is there are versions that use 4 relays & others 5 which is what you are doing. And for the early ’97 & ’98 the OWM relay used such that when on high speed all power is through the relay so there is no need for one for high speed even though I have seen 4 used for them too.

As for the light green wire, if you use dark green wire for grounding as you need to the small light green wire will be OK. Actually when on a/c & defrost that wire connects to the black ground wire to turn the compressor on so it is a grounding wire to the compressor relay too. The mode switch connects the dark green wire to the black whenever the fan is needed which is in all positions except off. So you should have 2 separate circuits in the mode switch, for ’99 & later both are grounding circuits.

5 Posts
Discussion Starter · #3 ·
Thx for the reply
I should be wiring the relays power 12v to the 85 terminal switches to the 86
Ground daisy chained to the 30 and the
Harness side to the 87
That would allow the rest to function as seeking ground to complete the circuit
The 5 relay write up suggests running 12 v through the ground DK green wire that’s the confusion on my end
Our Jeep is a 2000 and that era is unique
So I told , past model and post model equipment revisions.
It is ground switched as I can tell
I understand somewhat but still learning
Electricity is all about potentials
And I question my potential in this area.
Let me know if this sounds right
I’ll do one yo and bench test it

4,668 Posts
I think the 5th relay you mention using 12v to the dark green would only apply to the ’97 & ’98 circuit.

Personally I think the 5th relay is redundant & not improving the overall circuit but that is just me. It has been a long time since I looked at a 5 relay setup but as I recall (might be wrong) that one is to trigger the 12v to the 85s which I think is to use as a switch to shut the power when the key is off or maybe to kill the ground when the mode selector is off. Either way if you get the 12v from the fan motor’s relay 12v which is from fuse 8, a red/dark green wire & also goes to the temp control switch & could be spliced into there it will turn the relays “off” with the key off & if you ground the 86s by connecting them to each of the 4 speed switch wires then keep the 5th switch wire which is the dark green one that goes to the mode switch it will turn all relays “off” when the mode switch is off. This way the fan goes off when the mode is off (good) & the fan off if the mode is left to an on position & you turn the engine off (also good) just like the non relay mod OEM circuit does.

It does not matter if it is ’00, ’01 or any other year. Other than maybe a wire color change all ’99 & later TJs (to ’06) with a/c have the exact circuit setup.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.