Phil's MY99 cab Cooling journal

This thread is based on my work to get cooling under control on my MY99 cab. So on with the content ... Today I installed the new passenger side cooling fan with total success. Low speed works great, stronger than I expected. You can easily hear it if you walk around to that wheel. And you can feel it with your hand etc. That's how I discovered (today) that the driver side fan is not working on low. It works on high. So I'll need to repair it using a spare ballast I have. Honest to goodness, the hardest part of installing the fan today was jacking the car up: 1. I'm working in my driveway, which is level front-to-back, but very slightly sloped down toward the street (drivers side for me usually). 2. Floor jack rear passenger side, to get jack stand under front passenger side. - Requires a couple inches lift (board under rear tire) to get standard jack under, no biggie long as you have a board. - Last time I did this, the floor jack started moving toward the street, which sucked for peace-of-mind. So this time I put a board there and kept it from moving, which sucked even worse, because the jacking point moved away as it lifted, almost halfway off the pad. - I'd blocked the front and rear wheels (driver side), as every jacking article says to do. - I'd also put on the parking brake and put the car in first gear, as every jacking article says to do. - But then I read last night a poster who said leave the car in neutral and no parking brake, "to let the car rotate as it's lifted". - Bottom line, there's some variables here, and I think I'm gonna go back to watching the floor jack wheels move as I'm jacking up the car. 3. I'm going to be jacking the car alot, to work on that driver side fan, and clean out drain ports under both wheel liners.

How did you know that you had a cooling problem to begin with? Just via your Temp gauge? I'm in San Francisco so my '99 cab rarely sees any real hot weather. I'd like to know if my fans are working or not before I drive out into the heat...

Yes, just via my temp gauge, which actually works pretty darn well, given all the bashing it gets. I was running between the zero (in 180) and the next mark (which is 250), so 220-230 (too hot). You want 180-200. Turns out my left and right fans were not running on low speed, which is not good, bcoz they are the first line of defense, supposed to kick on at 180-186 and hold it there. Easy way for you to test your low speeds. Start the car, then press the snowflake (A/C). You should immediately hear the relays click and fans start (listen closely). Verify by walking to each front wheel (just in front of each), kneel down. You should hear the fans, and feel air moving (put your hand down there).

Doing much better now, but not quite there yet, until I fix the low speed fan on the driver side. Today was the first test run with the new fan, and there were things on both fans and relays I needed to check. Here are the results: A. Engine (coolant) temps below 180 (new fan only): (1) Low speed works while "6C" temp display active. Result = success. (2) Low speed automatic mode works (per coolant temperature, not manually). Result = success. (3) Note - Temp. holding steady lower and longer at 180, then 200. This is due to one fan low speed working now (vs. zero before). Eventually though, temp. rises above 200 and continues rising (as before). B. Engine temps above 180 (both fans): (1) Hi speed works. Result = success (both fans). Nice bonus - high speed turns on/off per temperature. Hi speed turned on at 108C, quickly cooled temp. to 104, then automatically switched to low speed. (2) Note - New fan improving max temp management. Took much longer to rise from 102 to 108 (idling in driveway). This is due to the new fan (low speed) running. (3) Note - freeway driving, 6th gear, 70mph, temp. slowly rises 91C - 98+. This is still unexpected. I thought wind speed would prevent rising temps at these levels. Next step(s): 1. Fix low speed driver side. 2. New water pump. 3. New thermostat. Probably 160F (low temp), reason = risk/reward for car which has always run hotter than others from day 1. 4. New coolant hoses. I can squeeze them with my hand. Wish dealer would've noticed that last week when they did coolant flush.

Today successfully fixed low speed fan (driver side) by swapping in a "donor" ballast from old passenger side fan. Attached is photo of donor ballast, removed from its old connector, but still attached to its old motor. Steps: 1. Prep donor ballast. (a) Determined it was good with multimeter, .5 ohm resistance between hi and low wires. (b) Unplug hi and low wires from connector by sliding gate with knife. This was awesome, because you can now just plug these wires into the connector on the car (no splicing). (c) Repair wires. The motor wire had damage in 2 places, so just cut off the bad section. Was prepared to repair using liquid electrical tape and heat shrink, but didn't need to. (d) Cut motor wire and splice into waterproof heat shrink butt connector. 2. Remove bad ballast from car. (a) Requires removing fan frame (incl. shroud). In my case, to give me room to work splicing the motor wire. In the case of a purchased ballast, you need to solder 2 wires to fan motor. (b) Confirmed ballast was bad, using multimeter, by seeing infinite resistance (open circuit) between low speed wire (input) and motor wire (output). Noted high speed was good by seeing zero resistance between high speed wire and motor wire. Testing this way, input vs. output, makes sense to me. A different way to test is between low speed wire and high speed wire. I'm not sure why this works, but it's more convenient, because their contact points are more accessible than the motor wire's. 3. Install ballast. (a) Plug hi and low wires into connector. (b) Splice motor wire into butt connector of donor ballast. Turns out this requires a heat gun, hair dryer not hot enough. I had to use a bic lighter, which sucks. (c) Button up and test. 4. Complete success. 5. You can definitely feel each cooling fan on low speed by placing your hand under each radiator. 6. Of course I'd disconnected the battery while doing the electrical work. 7. I was confident it would work the first time, and it did, because I thought through every detail beforehand. 8. The floor jacking sucked. It moved quite a bit away from the jacking point and looked like it would move too far. I need to research that. Money wise I've now fixed both radiator fans (incl. passenger side all new) for a grand total of $168. The savings, $600, I contributed to my dealer service budget. .eot.

New bug observed, low speed fan did not kick on while CCD display was on. Engine temp. had risen high enough (212F) so low speed fan should have turned on at 206F but didn't. Then I turned off CCD, and then low speed fan turned on. This warrants further testing. Meantime keeping the snowflake on (compressor on) for reliability (fans always on). I've seen this behavior before with the high speed fans, but it was intermittent and involved the state of the snowflake button.

The only time I have had, discovered, an engine radiator cooling fan failure was in a construction zone stop-n-go traffic near Little Rock AT in August. Had to shut off the A/C to keep engine from overheating. A few miles down the road I came to the realization that the A/C could be used provided I used MAXIMUM cooling mode/setting. Drove all the way home to Seattle in cool comfort.

Big improvement now that both radiator fans are fixed. Today drove 40 miles, half of it freeway, in 85 degree weather. "Living on the 8" now. Needle holding steady on right side of the 8. Except stuck in traffic, then it moves to between 8 and 0. Even I'm a little shocked, it's that good. Big improvement on freeway, holds steady on the 8, no upward creep. A week ago, minus one low speed fan and minus air ducts and bumper cover, I had upward creep. Which I could never understand until I saw an old Macster post saying air flow is actually worse at freeway speed. I think the air ducts improve cooling significantly, based on today (with) vs. 2 days ago (without). Today's tests were with A/C compressor on. Next week I'll test with A/C compressor off, to test the "automatic" on/off fan action based on temperature. Very pleased with this improvement.