Sorry about copying this from the A/C Forum...it was a lot to type and I'm hoping that someone else had this kind of problem solved.

1993 Bronco, 5.8L, Converted to R-134a.

Alright...when the selector switch is moved to Defrost or A/C (norm and max), the interior air is warm. The a/c clutch does not engage, the pressure low side pressure is good, the low side pressure switch is closed (has continunity, checked with volt-meter), jumping the pressure switch does not start clutch. I checked clutch movement using the positive post on battery and grounded negative side, clutch worked with enging off. Did not try with engine running. I did not get any voltage across the a/c clutch wiring plug with the a/c turned on and truck running.
I took the dash apart and got continunity across the selector switch inside the truck for the 1st and 3rd wires (purple and Black w/Green tracer) when selecting defrost and a/c. No power across Fuse 6 (A/C Clutch) fuse on interior fuse panel nor power across selector switch wires. I checked wires from clutch to Power Dist. Box, no cracks or pinholes in wires to cause an interruption. I've had the truck for about a month, and the A/C has never worked.

What am I missing? Should I try the clutch with the engine running and A/C on? I also searched this issue in the Bronco forum and found that the Tachometer may be affected by this problem; and my tach is not working. I'm hoping that the problems are interlaced.

Again, you guys are the best. I did the sponsorship link just a second ago.

Tim

 

Funny you should mention that---! I have a 93 EB 5.8 that has been converted to 134a, but mine works . Do you have the EVTM for the 93? I have one around here somewhere.

 

sorry, EVTM? All the pistons aren't kickin and tickin in my head this morning.

 

No problem, I hear ticking in my head all the time, but means nothing

Electrical & Vacuum Troubleshooting Manual

It is a "Ford" based manual that contains diagrams for the above stuff. Can be ordered through "Helm" (manuals) on-line. Dont recall the cost, but not expensive and very well worth every penny! If you are inclined (appears you are) to do a lot of work yourself, then drink water for a few days and order one!

My experience has been that they are very good and accurate, even to other years. Ford generally keeps wiring colors and circuits the same.

I'm really busy right now, but maybe I could look up something and scan or fax to you------*#** forgot my scanner isnt hooked up-. Maybe I could dig through this stuff and find it!

PM me if needed-.

 

Here's what I found out today:

Low pressure Side: 54, High is 180ish


With a Fluke Multimeter and the engine running:

At fuse 6: Have power.

I have power all the way through the system until I get to the connection after the Low Pressure Switch. The pressure switch, when I tested the purple wire to ground, 12-14 volts, and the black w/ yellow tracer to ground I have 12-14 volts.

If I jumped from the low pressure switch to the clutch connection (and grounded out the other terminal on the cluctch), the clutch engages and spins. It puts a small load on the engine like a normal a/c would.

This leads me to believe that there is a short/ground out after the male connection at the low pressure switch.

Trying to chase these two wires after the switch is going to be the real test. If anyone has any ideas, I like to hear them before I try to fix the a/c with a hammer.

I'll try and figure out how to put the a/c diagram that I have as a picture in my account. Maybe this will help someone else along the way.

Tim

 

That Alldata sheet looks just like the EVTM (surprise, surprise).

C162 is the pressure sw on the dryer/evaporator.
Close to that is C106. C101 is on Drivers fenderwell, between the fuse box and the engine. As soon as both bleary eyes start to function, I will try to find pin-out for connectors. Maybe Alldata has the pin-outs, dont know. The BK/Y is the one you are chasing.

You didnt say if you had ~12VDC at the compressor clutch on the BK/Y and RTN/GND on the other leed (BK). If no 12V then you need to chase and verify 12V through 106 & 101. Also, the PCM can shunt the 12V to clutch for WOT to cut off compressor. That is located in the wrapped harness between C101 and clutch, but doubtful its the problem.

Sounds like you have enough pressure for the dryer pressure switch to stay closed also because you have 12V on both sides of the connector there. I am not sure you have enough high side pressure, but if ambient temp isnt very high (as ours in Fl is) maybe you wont have the high side pressure we usually do----maybe some refrigeration exp will know. Dont recall if you said you have done the R134A conversion or still R12.

Dont give up yet and do the hammer adjustment----just yet. You may find something kinda simple, a real forehead slapper !! LOL

 

Sorry that it took me so long to get back to this board. I have had a couple of issues that I needed to take care of.

For some reason unknown to me, there was a break in the Black/Yellow wire from the LPS to the 8x8 pin connector. I spliced a new wire into the line just after the connector, and then started the big boy. After putting the A/C on max, the compressor jumped to life. I was jumping and screaming around the garage and house like I was watching Clemson play football.

Thanks to everyone who had imput on this and I hope that this bit of information will help someone else in the near future.

If rewiring, use at least a 16 gauge wire. I used 14 after asking an electrician about 12/15amps.