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Pigeon-Rat - Opel gambler build

1966 Opel rekord mounted to 1990 Nissan pathfinder.
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Nothing is ever easy on this damn thing. Turns out I was looking at the wrong wiring diagram. I don't have the "manual" a/c, I have the "automatic", so a bit more complicated.
20250323_154401.jpg

The general connections for the a/c relay are basically the same, but none of the wire colors match.

As near as I can tell, the "push control unit" ie, the a/c button, is supposed to supply 12v to the thermo amplifier, ie the temp controller. The thermo amplifier provides GND to the pressure switch which passes that through the ECU and then on to the A/C relay. The thermo amplifier also provides 12v to the A/C relay.

If the A/C relay gets 12v AND GND, it closes and sends 12v to the compressor.

All of this is simple enough, but none of the wire colors match with any of the wiring diagrams I have, so tracing the wires is a nightmare. Also, when I push the A/C button, the relay clicks on, even if I have the pressure switch unplugged. :dunno: So, as near as I can tell, the A/C relay is getting GND from somewhere. I don't have the factory ECU anymore, so if I had wired it correctly, the pressure switch should be connected directly to the thermo amplifier. That doesn't appear to be the case, or at least the pressure switch is not connected to the A/C relay. So the pressure switch is not in the loop, and will have no effect on whether the compressor comes on or not.

When I started working on all of this, the compressor was getting 12v whenever the key was on, but was not connected to the A/C relay. I have no idea what I had it hooked up to, but obviously it was wrong.

Since the A/C button does activate the relay, I decided to just connect the compressor to the relay output and call it a day.




Chevy305 said:
Pull the connector off the compressor, put 12v on one side and ground on the other, see if the clutch actuates.
Click to expand...
The compressor is grounded through the case, so only the power wire is there. Once I got the wiring above done, I double checked to see if the compressor clutch would activate, and it did not. It was working before I swapped out the ECU and screwed with the wiring harness. My guess is that when I hooked up the compressor to a constant 12v source, it ran all of the time (without the system being charged) and I burned it up.

Gonna try and get a working compressor tomorrow from the junkyard.


If I get a working compressor the whole system should work. At that point, I'll see if the thermo amplifier is connected to the pressure switch. If it is at least providing GND to the switch, I can make the connection between the switch and the relay (they are near each other) and get that back into the loop.
 
You could go bone simple with a low side switch that closes the relay, but you could also let Megasquirt run it if you have the I/O available. The IAC could open a bit when the clutch engages.
 
I forgot to report back on the A/C fix. Replacing the compressor did the trick!
ashman said:
If I get a working compressor the whole system should work. At that point, I'll see if the thermo amplifier is connected to the pressure switch. If it is at least providing GND to the switch, I can make the connection between the switch and the relay (they are near each other) and get that back into the loop.
Click to expand...
I still need to add the pressure switch into the loop, but for now it's blowing ice cold, and pigeonrat is running well. In fact, I was able to run a gambler500 even a couple weekends back.

20250426_104912.jpg

I ran several hundred miles of dirt roads through central Utah without too much trouble. Right near the end, I lost the tensioner pulley for the supercharger, but pigeonrat runs 3 separate belts, so it didn't stop me. I was able to grab a new pulley in Cedar City before making the highway trip home.

I do have a nasty ticking that only shows up when the engine is really warm. I'm pretty sure it's an exhaust leak on the PS header. One of the exhaust to head bolts went righty-loosy on me, so I'm going to have to pull that one and heli-coil it. Hopefully that goes smoothly and resolves my ticking.
 
I took care of a few issues over the last week. First up was the exhaust leak.
20250518_212738.jpg
As you can see, each exhaust port only has 2 bolts (the left most shows 4, but those are for different style manifolts). The front most port was obviously leaking. The stud that is removed in the pic was stripped out. It's an aluminum head, so helicoil was pretty easy to do.

20250521_194207.jpg

After I got the header bolted back up, I fogged the exhaust system to make sure I didn't have any other leaks. All looked good, so I buttoned it back up. Luckily I remembered to remove the plug in the tube before I did so.
20250521_200758.jpg

Finding this leak was actually good news. Sometimes my lifters can be a little loud and I was worried that the ticking that I was hearing was a bigger problem. After a decently long test drive, no more ticking showed up, so I think the problem is solved.

Oh, and I was getting a very rich smelling exhaust before as well. Solving this leaking gasket appears to have cleared that up also.

Another problem I was having was the roof rack sliding around when I was getting a little too wild offroad. In this pic you can see how its slid off to the passenger side.
20250426_170434.jpg

It got way worse than that a few times, and pulled free the wires to my roof lights too. I decided the easiest way to fix it was to weld up some stops on the sides of the hold downs.
20250523_194004.jpg

It shouldn't be able to slide past that, so another problem solved. :)
 
Exhaust leak before the O2 sensor will throw off it's readings. Prob helped the fuel metering getting that fixed.
 
Unfortunately, it appears I have another problem. :cry:

When I changed the oil, I noticed what appeared to be some milkshake in the fill tube. I pulled the valve covers to take a look and the valve train all looked clean, and the was no water in the oil pan. However, the valve cover itself ha some recesses and splash plates that had milkshake in them.
Since I blew the head gasket awhile back, I thought maybe I just didn't clean the valve cover good enough and it was just left over from that. I made sure to clean it very well this time, then finished the oil change.

Well, after some more test driving I can see a bit of milkshake in the fill tube again. Definitely have aome sort of water leak into the head.

The engine runs fine and no water is aming it into the oil pan, so for now, f it. I don't know if I've got a cracked head or what, but I'm sick of working on it for now.
Ugh.
 
I've seen cars milkshake the oil fill cap in cold weather, with no signs of coolant loss or head gasket problems.
 
kgblazerfive said:
It could be condensation
Click to expand...
What he said. This is part of the reason short trips are so bad for your engine, it doesn't get hot enough to evaporate out all the condensation from combustion in the blow by. I'd take it for a nice long drive, then check to see if there's any "milkshake".
 
Truckman4life said:
If you got moisture in the engine from a previous failure it takes a long time to get that crap all worked out of there.
Click to expand...
I've now been on a couple of long trips and I keep having to add water to the radiator, and no leaks appear on the ground. Pretty sure it's a cracked head at this point. :cry:

That said, I can go a whole trip with only adding water once, so it's not leaking a ton, and nothing shows up in the oil pan. She runs great otherwise, so for now I'm going to ignore it. :P

Had a little fun with the gambler500 guys in Vernal last weekend. :cool:
View attachment pigeonrat donut.mp4
 
ashman said:
I forgot to report back on the A/C fix. Replacing the compressor did the trick!

I still need to add the pressure switch into the loop, but for now it's blowing ice cold, and pigeonrat is running well. In fact, I was able to run a gambler500 even a couple weekends back.

View attachment 504000

I ran several hundred miles of dirt roads through central Utah without too much trouble. Right near the end, I lost the tensioner pulley for the supercharger, but pigeonrat runs 3 separate belts, so it didn't stop me. I was able to grab a new pulley in Cedar City before making the highway trip home.

I do have a nasty ticking that only shows up when the engine is really warm. I'm pretty sure it's an exhaust leak on the PS header. One of the exhaust to head bolts went righty-loosy on me, so I'm going to have to pull that one and heli-coil it. Hopefully that goes smoothly and resolves my ticking.
Click to expand...
Is that a dryer and a chase lounge on the truck bed?
 
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