Intermittant Blower motor and A/C

[Ωhm]

1 hour ago, HellCreek said:

It is only when I switch the selector to A/C that the problem occurs and the breaker gets hot.

 

On 8/22/2023 at 2:55 PM, HellCreek said:

I have by-passed the low pressure switch with a jumper and eliminated that as a cause. 

 

Remove that jumper wire installed on the AC low pressure switch (C239). Determine if problem still exist when AC is engaged. If so, problem exist between C239_2 and Blower Motor fuse (circuit breaker).

 

[HellCreek]

1 hour ago, Ωhm said:

 

 

Remove that jumper wire installed on the AC low pressure switch (C239). Determine if problem still exist when AC is engaged. If so, problem exist between C239_2 and Blower Motor fuse (circuit breaker).

 

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.

[87MJTIM]

Press the "Alt" key and type "234"

 

Alt-234 = Ω

[Ωhm]

41 minutes ago, 87MJTIM said:

Press the "Alt" key and type "234"

 

Alt-234 = Ω

 

I never guessed using the Ω as part of my password would cause these kinds of problems. Need to turn NUM LOCK on.

[Ωhm]

1 hour ago, HellCreek said:

I assume that you want me to reconnect the low pressure switch, allowing the compressor clutch to engage

 

No leave the circuit OPEN (disconnected). If it still gets HOT, problem lies between C239 (AC low pressure SW) and C236 (AC Mode Select SW). This could mean the AC controller itself, but you mentioned you rebuild that.

 

 

2 hours ago, HellCreek said:

The reason that I ask is that I want to see if a short-to-ground exists along that wire using an ohmmeter.

 

Yes. Do a wiggle test.

 

 

 

2 hours ago, HellCreek said:

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?

 

The function will not matter as to which way the connector is connected. But one side goes to the AC Mode Select SW and the other side feeds Splice_B.

 

 

 

If all looks good, wiggle test the Splice_B side of the harness.

[HellCreek]

20 hours ago, Ωhm said:

 

No leave the circuit OPEN (disconnected). If it still gets HOT, problem lies between C239 (AC low pressure SW) and C236 (AC Mode Select SW). This could mean the AC controller itself, but you mentioned you rebuild that.

 

I did that and yes, the breaker still gets hot, though it takes longer.  There is a 4 wire connector behind the radiator overflow bottle.  I disconnected the battery and did an ohm test on those wires, since it was in the same loom as the AC low pressure wires.  There was a green with black tracer - 0 ohms, an orange with black tracer - full continuity,  a black with white tracer - 0 ohms, and a solid green - 2.97 ohms; all on the 20 K ohm scale.  There is also a relay next to the remote power steering reservoir that is in the same loom.  I disconnected that, cleaned the contacts and reconnected it.  I have no idea what that goes to.  I removed the split loom from the harness routed in front of the radiator and could find no splices in the wiring.  Where is Splice_B that you mentioned?  After al that the breaker still gets hot.                                                                      

 

 

Yes. Do a wiggle test.

 

 

 

 

The function will not matter as to which way the connector is connected. But one side goes to the AC Mode Select SW and the other side feeds Splice_B.

 

 

 

If all looks good, wiggle test the Splice_B side of the harness.

 

[HellCreek]

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

[Ωhm]

I'm using the 1988 Electrical Manual. They claim its close, but maybe it not.

 

_mj1988electricalmanual_1.pdf

 

 

Page_36 shows Splice_B and page_87 shows location of Splice_B. This splice will appear with the letter (B) within a circle. Look at lower left hand of page_87.

 

Odd I can't find any 4_pin connector. yet.

 

AC Clutch Relay C241 is shown on page_87.

 

If AC low pressure SW is disconnected and it still gets HOT, problem lies between this C239 and C236_A.

[HellCreek]

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.

[Ωhm]

On 8/18/2023 at 4:24 PM, HellCreek said:

I have also confirmed that there is a 30 amp breaker where the blower fuse should go.

 

Excess current flow, shorts to ground will cause heat but so will a voltage drop at the breaker itself. What I'm wondering is do you have a faulty circuit breaker.

[HellCreek]

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.  

[HellCreek]

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

[Ωhm]

With bulkhead connector disconnected, does the Circuit Breaker (CB) still get hot?

 

EDIT:

Disregard, No Ignition SW, but with a long enough jumper you could backfeed that CB.

[HellCreek]

How would I backfeed the circuit breaker?

[Ωhm]

1 hour ago, HellCreek said:

How would I backfeed the circuit breaker?

 

Is the CB in the same place as the Blower Fuse would be? If yes, disconnect the Horn Relay (C192). With connector disconnected apply 12vdc (fused jumper) to C192_B. IGN_SW key must be in the OFF position, otherwise you'll be backfeeding the IGN_SW itself. Also, make sure bulkhead connector is separated. 

 

 

[HellCreek]

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?

[HellCreek]

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.

[Ωhm]

54 minutes ago, HellCreek said:

I would still like to know what the horn relay trick is supposed to show.

 

As far as I can tell, problem circuit is both, under the hood or under the dash. With bulkhead separated and backfeeding the fuse could prove out 'under the dash' as GOOD or BAD. 

 

Lets hope the 25 amp fuse never blows and this problem just goes away. Wishful thinking here.

[HellCreek]

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?

[Ωhm]

15 minutes ago, HellCreek said:

So, if the fuse blows, the "under the dash" circuit would be bad?

 

Yeah. With bulkhead disconnected, it's got to be under the dash.

 

Fuse/Circuit Breaker question. If CB trips faster might be the way to go. I don't know if I like that CB, but you try another one before and the new one still got hot.

 

With bulkhead disconnected you might have to go straight to the battery for voltage source. Keep in mind wire size. We're dealing with a 30A_CB or 25A_fuse. Don't want to turn the jumper wire into a fusible link.

[HellCreek]

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

[HellCreek]

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.

[Ωhm]