Front Windshield Washer problems - 89XJ

My '89 Cherokee front washers don't work.
The wipers will work with the pump harness unplugged, but when I plug it in, there's no spray, and they'll either wipe once or not at all. The front pump works, because when I attach the harness from the rear pump I can get a spray on the windshield. There's power at the harness to the pump when it's unplugged and I actuate the wiper switch, but when it's connected to the pump it's a big no-go. When I attach the front washer pump harness to the pump for the rear, I get no juice out back, but the rear pump is brand new and works great with its own harness attached.

I tried disconnecting the intermittent wiper module and bypassing it, but there was no change. The 4.8A circuit breaker appears to work, but it seems like that I'm getting too much draw with the pump and wipers running, and it trips the breaker.

Obviously I can't replace the breaker with a higher amperage one, unless I'm trying to burn the Jeep down, but I'm still not sure what my results mean. Is there a short somewhere? I'm not the most skilled guy with wiring or electronics, and I'm not sure what else to try besides throwing a ton of parts and money at it. Please advise me as to what the obvious thing that I'm missing is.

do you own a multimeter?

Do you know how to use it?

You say that the breaker appears to work, is it tripping when you try to run the front pump?

I'm fairly sure that the washer pump and the wipers are fed from different fuses/circuits, but I'm going to have to look in the FSM on that, or actually go outside and look at my junk.

I've got a multimeter, and I've got a basic idea on how to use it, but it's been a long time since I've last used one. It's entirely possible I'm using it incorrectly, maybe I'll dig out the manual for it (wherever that got stuffed).
I think the breaker is working, I can hear it click when I try to run the pump, so I'm pretty sure that's tripping it.
I was glancing at a wiring diagram in my Haynes manual, but I don't think it's entirely accurate. I just printed off a service manual at work on Friday (don't tell my boss how I spend my overtime), and it seems like a more accurate diagram based on comparing it to my set up. I'll look at that when I head out to the garage tonight.

Another fella suggested a bad ground, which I had at first dismissed because the circuit is completing, but maybe it's just dirty, or partially grounding and causing enough resistance to trip the breaker? I'll test it out by throwing a new ground wire out to a ground that I know works, and see what happens.

Thanks for replying by the way, I appreciate any help I can get!
Sean

I had the same issue in my 89 and it was high resistance in the wiper switch itself. Being an MJ (and too lazy to tear into the column to replace it), I installed the dash switch for the rear wiper and use that for the wash function instead. I also considered installing a relay and have the switch trigger the low current relay instead.

I think my problem might be the switch as well. I've tested and eliminated everything else in the circuit.
I pulled the breaker and put a 5A fuse in its place, which changed nothing, and didn't blow the fuse. I tested the intermittent wiper module, and it read 0.3 ohms resistance across the washer circuit (pink in to violet w/white stripe out). Not trusting my multimeter skills, I bridged it with a spare chunk of wire, and still no change, which eliminates the module. I tried a new ground, which I tested first, and still no washer function. I double checked the pump again; it works with the rear wiper harness attached, but not the front harness. I tried a new pump on the front washer harness, to no avail. I ran a new wire from the IW module to the pump, and checked it with both grounds, to eliminate the rat's nest of wires, still nothing. As far as I know, there's nothing else in the circuit, so it has to be the switch. I am getting just under 11 volts at the harness, which is I guess not quite enough to run the pump.

I was considering the relay option also, or getting a second rear wiper switch and wiring it to the front washer. I don't relish the idea of pulling the steering column apart, and I'd hate to get a switch from the wreckers only to find that it's also FUBAR.

Thanks for your advice 87manche, and thanks for relaying your experience and confirming what I was thinking lawsoncl.

P.S. Apologies for the long posts, I've never been able to grasp the concept of brevity.

11 volts should be enough to run the pump. Sounds like you're getting voltage but perhaps not current. Did you measure the voltage with the pump attached?

Good job with the troublshooting, I was going to suggest replacing the breaker suspecting it had internal resistance problems, but I see that it made no change.
So to sum this all up.

Pump is good (checked on rear harness)
You've got 11 volts on the front harness
you tried a new ground, at the pump?
bypassed the breaker
ran a new wire from the intermittent module.

Have you inspected the connectors on your IW module? Mine were horrible and required repair.

You found the wires from the column switch under the dash? You could try jumping them to confirm the switch itself is bad. As I recall, I was seeing something like 200 ohms across the switch when activated.

I tried a new ground at the pump, and the connectors were making contact at the IW module.
I hit up the local Pick N Pull yesterday, and grabbed up a couple goodies. I skipped trying to replace the switch in the stalk, after fighting with a few steering columns, I realized it was going to be more of a headache than it was worth. I ended up wiring in a relay last night, and it got the problem sorted out.
Thanks again for all of your help gentlemen.