Timmaay

Here is a follow up post for future reference since I finally figured this out. First off a big thank you goes out to 1987Comanche for answering a ton of questions in my attempt to decipher OE wiring diagram How these Bosch style relays are supposed to work: I started to type a description of how they work but this was better. http://www.bugmanweb.com/gsxr/relays.html As stated in earlier posts, my problem was that when I turned on the a/c in my truck the aux cooling fan did not turn on with it. The cooling fan is supposed to turn on when either the temp switch closes or you switch on the a/c. I drew up a simple diagram in microsoft paint to help see where all the wires were connected without having to physically trace them every time in the truck. Keep in mind the wiring in my truck is not OE, somebody else wired it when A/C was added. Here is that diagram. Ok so our knowledge of relays tell us that pin 30 is constant power, 86 is switched power, 85 is ground, and when 86 is energized, 30 essentially connects with 87. On my diagram you need to know what the four wires off the connector are. I figured out (by poking around with a volt meter) that orange is power when the truck is running, green is power when you switch on the a/c, and blue is ground. If you follow the power around through the wiring it actually makes sense (keep in mind that the a/c low pressure switch is normally closed) and in fact the fan should turn on when you switch the a/c on. Because when you turn on the a/c in the cab and power is routed to the a/c clutch it would also be sent to pin 87 of the fan relay which is the power for the fan. Well guess what, it wasn't getting power. I figured out that the diode was bad and it wasn't allowing any power though. Basically diodes work like a one way valve, they allow current to flow through but not back out. Now the reason the diode was there to begin with is that if the temperature were to close because the truck was beginning to overheat power would also be sent back to the a/c clutch and turn it on too. I didn't like the idea of a diode on the main power circuit so I added a diode I got off a cherokee from the junkyard. This diode has two inputs and one output. The middle wire is the output. Test yours for continuity to make sure. This is what I came up with and I works great so far! I may add a manual in cab switch later on. Keywords for searches aux auxillary auxiliary cooling fan A/C air conditioning zener

That plug was left by the factory for dealer installed A/C. I used one of the pins to provide key on 12V+ for my fan relay (not load, just trigger). This way the fan won't come on if the truck is shut off. Sure. It might be best to PM me and take it offline. Perhaps you can document rewiring the relay and put in the how to section. You can give me honorable mention :) All right. Let's give this a shot.

Somebody did some splice and dice funny business... These four wires continue all the way over to the ac compressor and some sort of switch, like a low pressure switch? And they go to the ac relay. Is this plug even supposed to be here?

Yes, this will work for the time being. Hit the JY and cut the connector off a temp switch. Then you can wire a switch to that pigtail that can be easily removed. I did trace the orange wire back and there isn't a diode on it. It looks like someone totally rewired the fan relay. Which is probably why it's not working properly. I'll take some pics. The previous owner didn't do any work himself but he had a ton of work done to the truck, and saved every receipt/ work order. I looked through the giant folder of stuff and found something from 1995 that said the a/c fan was not coming on. Apparently the mechanic advised him that it was possibly a relay. But no work was completed. So I don't know where and when someone messed with it, but we know that it has had this problem for a while. I would really like for the fan to work as designed and have the option of turning it on manually. I will need help re-wiring it though. Are you up to a barrage of questions?

I think I'm going to just add a switch to turn the fan on manually for the time being. A jumper controlled by a switch across the two temp switch wires should work fine right?

This diode only has one input and one output. I took some pictures. I hope you can see the differences. And there is no little orange diode to be found.

I went to the local pick n pull to try and get another diode. Both of the cherokees had different wiring than on mine. I saw what you meant about the diode being a little orange thing, unfortunately my truck doesn't have that. It's got a diode that looks almost like this one. http://www.napaonline.com/Search/Detail ... 0217876969 One end has a bullet type connector that goes over the threads and the other end was soldered. It was heat shrinked and everything, looked factory to me. Don't think someone messed with it before. But Why is my wiring different? The cherokees both had A/C. :dunno:

Thanks for the offer! I will try and see if I can get one locally first, if not I will let you know. I did jump the switch and the fan came on. So if the switch is good, the fan should work when the engine begins to overheat... I pulled the diode out of the wiring and tested for resistance and it's got infinite resistance both ways. Failed open? Sounds like the culprit. But what would cause it to fail?

I think that you are right about the diode. Do you know which kind I need and where the best place to get it from is?

Truck is an 89 4.0 auto with factory A/C. I recently learned that when you switch the A/C on, the auxiliary cooling fan is supposed to turn on as well. Mine does not. I think the fan turns on if the engine is starting to overheat but I am not entirely sure about that. I have tried following this tutorial but I am stuck. http://www.lunghd.com/Tech_Articles/Coo ... gnosis.htm If i supply battery voltage to terminal 4 of the relay connector the fan spins. So, the motor works. Next is says "With fan relay removed turn the ignition switch to the RUN position. # Check continuity between terminal 5 of the relay connector (Fig. 43) and the body ground con- nections on the fender panel back from the relay con- nector (Fig. 42). If continuity exists proceed to next step. If continuity is not found repair open." When I perform this test I get an open circuit. If you trace the wire that goes to terminal 5 it is the coolant temp sensor/switch. Isn't that supposed to be open until a certain temp? Or is it the other way around? Also in the factory service manual pdf that I have for an 88. The procedures for testing the fan are nearly word for word but the relay pin diagram is different! 4 and 5 swapped. (The pin id that i was using in the test is the non factory identification.) Another question: If the A/C is low on freon does this prevent the cooling fan from running??? :help:

Sometimes when I started my truck it would rev way up to 2500 rpm and stay there. I would shut it off and restart, sometimes it went away other times not. But, by unplugging and reconnecting the TPS, it fixed the problem everytime. I have a different TPS in there now and I have not had the problem since.

Thanks for the info Eagle. I won't worry about the oil pressure then. What I am still worried about is the noise at cold start up. I talked to my uncle about it and he suggested that it may be a leaky or sticky lifter. Does that sound reasonable? I don't drive this truck all that much and when I do do it's only short trips. Could that be a contributing factor?

I should have mentioned hat the oil pressure used to read fairly high, now it is a bit higher.

From the back of the jug: Meets API service CJ-4, CI-4 Plus, CH-4, CG-4, CF-4, CF/SM Meets the performance requirements of ACEA E9, Mack EO-O Premium Plus, Caterpillar ECF-3, ECF-2, ECF-1A, Cummins CES 20081, DDC 93K218, MB Approval 228.31, MAN 3275, MTI cat 2, Volvo VDS-4, Deutz Dqc III-05, JASO MA

No I don't know which oil was in there before. This is the first oil change I have given it since I bought it. What are the chances that the oil filter is faulty? :hmm: Should I go out and try a different one?

Background: Truck is an 89 4.0 AW4 with 126,000 miles I recently changed the oil in my truck to Rotella T 15w-40 and a NAPA 1626 Gold filter. I changed the oil because my engine seemed a little noisy compared to my friends 4.0. I suspect lifters or rocker arms or something around that area. I am far from an expert but it definitely seems to be coming from the top end. With the oil changed the truck seems a bit quieter but not where I'd like it to be. The Problems: Upon cold start up it now sounds like it is not getting oil for a second or two. Sounds like a loud CHUH CHUH. What do you guys think? The temperature around here never gets below freezing so I thought 15w40 would be fine? The oil pressure gauge also reads pretty high. Like 70 or so at a cold idle and then down to 40 at a warm idle. The guage will go up to 80 when I first start driving after a cold start. I don't have a mechanical gauge to check the accuracy.

Nope. Just very well taken care of by the previous owner. It even came with all the paperwork including the factory window sticker and original build sheet! nice. mine has.... um..... self produced ventilation holes lol Ahh yes, you mean it has a complete cold air intake system installed. :brows:

Nope. Just very well taken care of by the previous owner. It even came with all the paperwork including the factory window sticker and original build sheet!

no thats nonexistent. lol anyone who finds one un restored 100%rust free and leak free will be my hero Like this?

Thanks. Yeah, it was spinning perfectly true and the rubber was the only give away. Well, and the fact that the pulley had managed to walk out about 1/8" from flush. But since I didn't know what a good one was supposed to look like, I didn't really suspect it. But now I know and will always know. :thumbsup:

:banana: All fixed! It was the harmonic balancer.

Good news, I took the Jeep over to a neighbors house and he pointed out that the harmonic balancer has moved out quite a bit. You can definitely see that it doesn't sit flush and that the rubber is a little dislodged. What appears to be happening is that since the harmonic balancer is moved out it is pulling the belt out with it causing the belt to slip and whine on the waterpump pulley. So, we are going to give that a shot tomorrow.

No way of telling mate. I don't like "rebuilt" or "remanufactured" parts, always buy new stuff if available, but w. our old junk, it's not always possible. Sure the vendor guarantees the part, but something like a waterpump is a major PITA if you have to swap it out 3-4 times before it's finally right. I'd rather spend the extra $$ to get a new or NOS OEM part if available and save myself the aggravation and/or possible engine damage. Hope it lasts a looooong time. :cheers: Thanks for the kind words Hornbrod. I just found out how long this one will last before it starts squeaking. 3 miles!!!! :wall: :wall: :wall: This pisses me off. The only thing I think it could possibly be is the power steering pulley. It has a slight wobble to it. Perhaps causing the waterpumps to die? :???: How hard is it to replace one of those, I know you were talking about having to press one on earlier.

Ok, finally was able to get the water pump swapped. Had a bunch of hangups, but I got it done. Started it up and the engine is super quiet and running extremely smooth! :D The belt is not wandering at all! I can only hope that this will last. But, what if the bearings on this pump fail too. Then what?

Do you? Well, I would attach the files here but I don't think it will let you. Might be best just to sign up. naxja isn't free is it? Yeah it's free to register for the forums.