Wiring: Fans
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Current Status. The project is so close to being road-worthy that much of the rest of my life is currently on hold while I make the final push. After starting the engine for the first time last week, and moving this Isuzu-Chevy combination under its own power for the first time, the engine hasn't been started and the vehicle hasn't moved. This is for the following reasons:
With temperatures exceeding 100° F lately, I knew I needed to get the radiator fans wired up.
There was no air filtration when it was run last week, and I really need this before I start loading up the engine.
The vacuum-assisted power brakes in this Suburban were workingagainst me when there was no vacuum. So, I needed to get that system up and running.
I thought it wouldn't be too difficult to get all of these things together by now, but it has taken longer than expected.
Intake system components were being trial-fit today--the subject of a future post. Wiring harness and other lines are in temporary disarray to make space.
My "barn" workshop has great solar gain, and quickly outraces the temperatures outside when the sun is shining. Even with strategically-placed box fans to move air through the structure, I wind up staring down at my engine bay through glasses with sweat pooling in them. It gets dangerously hot out there, and my northern European genetics don't get along with heat! The scorching heat of my workshop will certainly become a self-reliance subject in the future. I want this workshop to be more comfortable for working year-round without being horribly inefficient. Meanwhile, I'm forced to get up early in the morning to do this work, when I can take advantage of the coolest temperatures of the day.
I found out that my salvage yard find of a Volvo 760's vacuum pump isn't up to the task of providing enough vacuum for the brake booster. It can't pull enough vacuum, and it can't keep up. Today I examined the costs of switching to a Hydroboost system, which uses the power steering pump's hydraulic pressure to assist braking efforts. These also have the benefit of a smaller footprint at the firewall--something that might be very important if/when I upgrade to a larger turbo. For now, I realized I could get a good pump for a fraction of what the Hydroboost components would cost.
The intake system is proving to be slow work, though I fabricated most of the components today. Working behind the engine on this is difficult, but the turbo's rear-facing inlet, combined with the Suburban's firewall geometry, doesn't give me any other options. I'll cover this in another posting when the intake is complete. Look for the silver pipe and red silicone elbows in the photo, and you can see where it's going to be run.
Using a pot of water a thermometer, and a light to test and set the fan controller's temperature.
This Post: Fan Wiring. I succeeded in moving forward with the fans, though! They are done and completely functional! I started by pulling out my Hayden 3647 fan control unit, a 12v supply, some test leads, and a test light to play the role of "fans." I put a pot of water on the gas stove with a candy thermometer and the fan controller's temperature probe in it and started warming things up.
The stock radiator on the 4BD1T starts to open at 180°F. When it opens, the radiator should be given a chance to do its job before the fans start up. When the vehicle is moving, the fans shouldn't need to run at all. When stuck in traffic on a hot day, the two 16" electric radiator fans I've installed should kick in, when necessary, to move air across the radiator and air conditioning condensor. After hunting around, I found the recommendation to set the fans to turn on at 200°F. The Hayden 3647 is adjustable, so my intent was to set the turn-on temperature using this apparatus.
Why electric fans? (1) I saw where others who put 4BD1Ts into their vehicles modified the stock fans by clipping them down and rigged up appropriate cowls (sometimes) to make them work. I didn't like that approach. (2) Mechanical fans, though they have viscous clutches on them, are an unnecessary source of drag on the engine -- even when they are freewheeling. Additional loads on the alternator will also drag on the engine, but when the fans are off (probably 95% of the time), there will be no fan-related drag. This project's main goal is fuel economy. This decision should help that objective, along with low rolling-resistance tires, a manual transmission, and overall gear ratios that target 1900 rpm at 70 mph in 5th gear. This engine's peak torque and fuel economy are found at that rpm. Every little bit helps, though!
I wound up trading the candy thermometer for a meat thermometer, because I noticed lag in the candy thermometer. The meat thermometer -- though I had to support it with a free hand -- had a very fast reaction time. I found out that the stock setting of the Hayden unit was way too low -- only 160°F. Later on, by actually reading the instructions, I found out that they purposely give it a low setting at the factory. I cycled the water temperature, while twisting the screw on the control module. Eventually, I got to a point where the system would turn on within a degree of 200°F. There is some hysteresis in this controller, so it shuts off again at 190°F.
Modifications made to the fuse/relay center under the hood. A fuse previously used for ignition purposes now provides an "on" trigger for the fan and vacuum systems.
After I had this set, I looked at how I was going to wire this up in the Suburban. At the fuse/relay center under the hood, I found two accessory posts. I thought that these might be switched on and off with the ignition/accessories, but found that they are always hot. So, I popped the relay center open and flipped it over. I spliced in the white wire shown here, attaching it to one of the switched pink wires. I made sure to use a wire from the correct side of a fuse so that this wire would be fused. The fuse used was for "IGN-E," which shouldn't have much to do, anymore, with no ignition system to supply. In the picture there are two eyelets shown, one for the fans and one for the vacuum system. These went to one of the posts, while the white wire was run out of the box as a trigger for those systems' relays.
The Hayden system turns on the fans when it receives a signal that the ignition switch is turned on, plus one of two other inputs. The first is obviously when the radiator temperature probe (inserted between fins on the radiator near the location where hot coolant enters the radiator) reads a temperature above the set threshold. The second input is from the air conditioning compressor. When the compressor is on, the fans will run--primarily to pull air across the condensor.
The fans were wired up and ready to go. The controller is below the battery and next to the power steering pump reservoir in this picture (hard to see).
I had previously installed the fans, so now I simply needed to hang the controller and run wires to the fans. I used electrical tape to keep the wires in neat bundles, surrounded them with convoluted tubing, and zip-tied them to the fan supports near the top of the radiator. At that point, I turned on the ignition switch to test the system out. Naturally, the radiator was cool, and they didn't turn on. So I jumpered the A/C wire to activate the fans. These things move a lot of air!
I wish I could say that the pump was working well when I turned on the fans for the first time. I will discuss this subject when I get something that actually works installed. I ordered some parts today.
-My recipe for success: free markets, more diesel, and less government!