When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Stock Grand Cherokee Tech. All ZJ/WJ/WK Non-modified/stock questions go here!ZJ (93-98), WJ (99-04), WK (05+)
All ZJ/WJ/WK specific tech questions asked here!
Hey all, for some reason, unknown to me, the guy that built my engine years ago replaced and hard wired the electric radiator fan so it's on when the key is on... I don't like this and want it to work like it should. I am not however, sure how to put it back the way it should be. Any help would be appreciated
Okay, I'm working from the circuit for the 4.0, so bear with me. Underneath the right front headlight support facia, there is a pulse-modulated relay controlled by the PCM. The PCM reads the temp gauge and turns on the fan relay accordingly. Up until the engine reaches operating temp of 210*, the fan doesn't run at all. At that point it starts running on high, dropping to low at 195* and runs constantly on low until you shut the engine off. There are only 2 wires going from the relay to the fan and low speed is produced by "pulsing" the power to make it run at a slower speed. If the engine temp goes above 210*, the fan returns to high until the temp drops. The relay gets hot so that's why it's located ahead of the radiator. Some people have relocated it inside the engine compartment for ease of access, but they don't last long there because of the heat. Included is a pic of it's location;
Later models use 2 regular relays and a 3 wire fan to control the speeds, but they are still controlled by the PCM. These relays are located in the PDC under the hood.
Last edited by dave1123; Apr 11, 2017 at 08:20 PM.
Makes perfect sense, and that looks to be the harness end that's hanging inside my wheel well now, two wire harness plug? There is a relay wired to the fan that's actually marked for the fan I believe... But for whatever reason the thing runs constant on what it seems is high.
Well apparently it isn't because that other looks like a 3 pin harness but either way, that's what I have in the jeep, maybe I can locate the original and wire that back in or try to figure out how to make it work again. He said he put a temp switch in but if he did, why wire it direct then? Mind you it was owned by someone in between and there was a black switch on the dash that didn't seem to do anything and the guy I got it from said it used to be wired to the fan. Guess the other question is, is there a way to by-pass all the random other s*** and wire in something that'll simply solve the issue?
The fan itself draws around 40 amps so I assume it has a supply relay that feeds the pulse relay. He probably took that wire and fed it straight to the fan. The PCM only uses 5 volts to control the pulse relay.
Yeah.... I haven't got a clue. It's got relays under the hood that idk the purpose of. Wires going here and there that don't belong. It's kinda scary lol
Idk if the mass of the wiring was done by the guy that built the engine and did the trans plus the lift... Hid conversion as well as the hella light install... Seems to me that someone capable of doing all that would have done a better job than what I'm seeing for the wiring in the jeep.
Why don't you employ the KISS technique? Keep It Simple, Stupid! Install a "stand alone" system with it's own controller and temp sensor. There are several good write-ups on this forum from guys that have done it. Bustedback comes to mind with his ZJ. At low speeds with a clutch fan, like rock crawling, it's not adequate to keep the engine cool, so guys install an electric fan as well.
Also, I've noticed on my 2000 WJ, there's enough room to swing a clutchfan as well as the electric one.
The only problem with JUST a clutchfan is long periods of idling can cause an overheat unless you watch the gauge and rev it up when it gets high. Also long periods of high torque and low speed, like slogging thru the mud or rock crawling can also cause high temps.
Yeah I'll likely use both but just wire the electric fan to a switch for those types of situations. That's likely my best bet. It'll solve the issue of that fan running all the time and I won't rum into issues with it overheating at low engine speeds
There is a easy and cheap clutch fan change out for the 4.0. It replaces the stock clutch fan set up and due to it's superior cooling ability, negates the need for a electric fan. The details are here. http://www.jeepforum.com/forum/f310/...astic-2892193/
Electric fan question...
