HellCreek

Hi, The ISA functions manually, that is, I can make it extend and retract using a 9 volt battery wired directly to the motor.

C215_1 has 12.2 volts. It was the relay towards the cab. The one in the front is the fuel pump relay. This is backwards per the FSM. Since I switched both relays, they both should be good. ISA is still not working. Thanks, Tom

I swapped both relays for new ones, since I didn't know which one was which. The ISA still did not extend.

HI, Thanks. Actually, I did remove it from the throttle body, and the motor does extend and retract the shaft. It won't activate on the truck when I turn the key off though. Also, if I extend it manually, it won't retract and idle down on its own either.

Does any one know where the jumpers go?

When I said that I knew nothing about electronics, I meant it. I need to know the basics, like - connect one end of the jumper wire to "x" and the other end to "y".

I will check that when I get a chance. By the way, how do you jumper the diagnostic sockets (near the battery) to cycle the ISA motor? I'm having to do that at the motor itself. I can completely overhaul an engine, but I know nothing about electronics. Thanks, Tom

Thanks for fixing that. ISA, I stand corrected.

I know this topic has been beaten to death, but this one is a little strange. I changed my ISA with a new one, replaced my intake/exhaust gasket and torqued the bolts, changed all of the vacuum hoses, cleaned the TB and replaced all the gaskets and o-rings. The problem is, as the title suggests, the ISA is not working. It does not fully extend when I shut off the motor like it is supposed to. I can extend and retract the shaft with a 9 volt battery, so the motor is working. With the ISA unplugged, I have extended the shaft with a 9 volt battery, left it unplugged and started the engine. It revved up to 3500 RPM, so I shut off the engine, plugged the ISA back up and restarted the engine. The RPMs stayed at 3500 and would not come down. I took it for a test drive, and when I returned, the RPMs were still 3500. I order to be able to drive it, I unplugged the ISA, retracted the shaft with the 9 v battery, and the RPMs now are at 800. I hate it when things don't work properly, so I would really appreciate some help figuring this out. I suspect an electrical issue. I have already checked the Closed Throttle Switch, and it is in spec according to the FSM. This is a 1989 MJ Sporttruck with a 2.5L engine and a manual transmission. Thanks, Tom

Sorry, I hit the wrong key. I bought a new harness from Octane Lighting on eBay. It also has ceramic sockets. I works great, and my headlights are much brighter. Thanks, Tom

Thanks, Guys, I bought

Hi, Does anyone have a link for the headlight relay upgrade?

This is an awesome post. My headlights just quit working, and I would like to do the relay upgrade. Does anyone have a link for this? By the way, all of the other lights work and the driver's side high beam works, but no headlights.

Just an update. It has been two weeks, and the 25 amp fuse is holding, and the A/C works as it should. I guess it just doesn't like circuit breakers. Everything I did needed to be done, new blower motor, cleaning the contacts, refreshing the grounds, etc. Thanks for all of the help and suggestions. This is a great forum with a lot of helpful people.

Thanks, I will try that. Before I do, though, I would like to see how long that 25 amp fuse lasts.

So, if the fuse blows, the "under the dash" circuit would be bad? Should I replace the fuse with the breaker for this test, since it trips faster? Also, should the 12v jumper come directly from the positive battery post to eliminate any of the Under Hood wiring?

On a whim, I took the CB out and replaced it with a 25 amp fuse. I ran the AC on Max (engine on with everything connected) for a good 5 minutes, and the fuse did not blow. For reference, the CB would trip in about 2 minutes. I am going to try this and see if it lasts. I will let you know. I would still like to know what the horn relay trick is supposed to show.

I wish I had known that before I reconnected the bulkhead connector. It is a pain to get to, or rather the screw connecting the two halves is hard to get to. Yes, the blower fuse has been replaced with a circuit breaker. What is this supposed to do, or what am I looking for?

How would I backfeed the circuit breaker?

Well, the bulkhead connector definitely needed cleaning, but that wasn't the cause of the problem, as it persists.

I thought that, too, so I replaced it with a new one - same results. The next thing I will do is open the bulkhead connector. I have a manual transmission, and it is possible that the clutch master cylinder has leaked into that and caused some corrosion. Sometimes I wonder where the designers went to school. Putting the master cylinder directly over the main electrical connector was not a very wise move. I cleaned the connector a couple of years age, but it won't hurt to do it again.

I looked for the splice behind the grill, and all I found was straight wire (no splices). That is where my 1989 FSM said it was, too. According to my FSM, the AC clutch relay is over by the battery, between the coil and the fender. By doing some wire tracing, though, I have found that you are correct. As far as the 4 pin connector goes, it does not show in my FSM either, but it is under the radiator overflow bottle. The wires are as follows: green - AC clutch relay black with white tracer - ? Orange with black tracer - power side of blower fuse and power side of AC Clutch relay green with black tracer - other side of blower fuse and one side of low pressure switch I have checked all of these with an ohmmeter, and none of them are shorted to ground. The problem may be from the fuse block to the AC selector switch. I will check that tomorrow. This problem has been getting progressively worse. At first the AC and blower would go off after 10-15 minutes of use, but lately it happens after about 2-3 minutes. Thanks for all of your help.

I forgot to mention that my tests were made with one lead on the fuse block.

Thanks for the reply Ohm (sorry, I don't know how to make an Omega). I assume that you want me to reconnect the low pressure switch, allowing the compressor clutch to engage. If the problem persists, as I am pretty sure it will, seeing the A/C system has just been charged professionally, where does the C239_2 wire end up; at the top or the bottom of the fuse? The reason that I ask is that I want to see if a short-to-ground exists along that wire using an ohmmeter. I have another question concerning the C239 switch: mine only has two terminals on the switch and on the rubber covered connector. Does it matter which way the connector is attached to the switch? I am guessing that this is simply an on-off switch activated by pressure in the A/C system and that either wire could be connected to either terminal - the same as a jumper wire.