Radiator fans not turning on

[DMC-81]

I can vouch for the heat on max trick to mitigate an overheating problem. Long ago I had a Jeep Cherokee and it began overheating on a highway though the woods late at night (no place to get help for an hour's drive). I cranked the heat to max and opened the windows. Although it was wintertime up North, the air coming out of the vents was hot! I also tried to keep the engine speed as low as possible using 5th gear.

This did the trick and it kept the temperature gauge below the critical zone. I watched the gauge for an hour till I got back to civilization. It turned out to be the thermostat that failed in the closed position.

Anyway, here is a picture of the D's otterstat jumpered if it helps:

image.jpg

[refugeefromcalif]

With my car, the heater has never had a good output of warm air in the winter. The temp doesn't get much over the first line on the gauge.
I suspect that my thermostat is stuck open. (It runs nice and cool in the Hot Alabama summers)...

George

[David T]

With my car, the heater has never had a good output of warm air in the winter. The temp doesn't get much over the first line on the gauge.
I suspect that my thermostat is stuck open. (It runs nice and cool in the Hot Alabama summers)...

George

Stuck open or maybe not even there! The motor really should be run at operating temperature for best fuel economy and longevity. Too hot is not good but too cool is not good either.

[funkstuf]

I like all the ideas above and I tried them all at one point or another, but, if the fans always kick on the first cycle or two, then stop working, then turn on again after the car sits for awhile, it suggests that the fuse/relay area may be getting too hot. I actually thought I needed to run my fans more so I used a variable otterstat that made my fans run more (similar to shorting the otterstat). Eventually, the wires at the fan-fail fuses melted, but the fuses remained intact. Shorting the otterstat will run the fans a continuously. I suggest after running continuously for awhile check the fuse wires on the fan fail (touch them) and see how hot they are and make sure they're not melting. I could never figure out the problem, but saw it happen to another PNDC member exactly as it had on mine. We both had the original fans and replacing the fans with new lower amperage fans solved the problems.

[sdg3205]

I like all the ideas above and I tried them all at one point or another, but, if the fans always kick on the first cycle or two, then stop working, then turn on again after the car sits for awhile, it suggests that the fuse/relay area may be getting too hot. I actually thought I needed to run my fans more so I used a variable otterstat that made my fans run more (similar to shorting the otterstat). Eventually, the wires at the fan-fail fuses melted, but the fuses remained intact. Shorting the otterstat will run the fans a continuously. I suggest after running continuously for awhile check the fuse wires on the fan fail (touch them) and see how hot they are and make sure they're not melting. I could never figure out the problem, but saw it happen to another PNDC member exactly as it had on mine. We both had the original fans and replacing the fans with new lower amperage fans solved the problems.

You're right. Sometimes the circuit breaker will trip until it cools down. I burned my fingers badly on it once.

[Bitsyncmaster]

I like all the ideas above and I tried them all at one point or another, but, if the fans always kick on the first cycle or two, then stop working, then turn on again after the car sits for awhile, it suggests that the fuse/relay area may be getting too hot. I actually thought I needed to run my fans more so I used a variable otterstat that made my fans run more (similar to shorting the otterstat). Eventually, the wires at the fan-fail fuses melted, but the fuses remained intact. Shorting the otterstat will run the fans a continuously. I suggest after running continuously for awhile check the fuse wires on the fan fail (touch them) and see how hot they are and make sure they're not melting. I could never figure out the problem, but saw it happen to another PNDC member exactly as it had on mine. We both had the original fans and replacing the fans with new lower amperage fans solved the problems.

A friend also had his jumpers melt and also flames from them. He also had OEM fans and I tested the currents and they were about 14 amps each. So either his fuse box gets really hot or the fans have an intermittent that makes the current go higher sometimes. I suspect the fans have intermittent high current. I installed a spare set of low power fans I had so I still have his OEM set. I may someday do some testing on those OEM fans. I wonder if it's just brush dust shorting the commutator. The low power fans draw 7 or 8 amps each.

[DMC-81]

I wonder if bad grounds at the fans, or dirty fans (inside) also cause the higher amperage load/melting?

When I refurbished that area, my fans also worked intermittently. When I spun them while the car was off there was resistance and there was a gritty sound. I took both of them apart, and found some dirt and rust particles sticking to the magnets. I cleaned all of the inside and also the brushes. Then I used a small amount of machine oil on the shafts. While it was apart, I sanded and repainted the cases. I also traced the grounds to the frame connection and cleaned that. I replaced the frame bolt with SS and used di-electric grease.

Anyway, now both fans work like new and the wires at the fan and the fuse area are cool. All for $10 in paint and a few hours of my time.

I remember Andre of the delorean world tour mentioning that they run the OEM fans because they pull more air, and they are user repairable.

Of course, YMMV, and I'm sure at some point they are too rusted/worn out, but I thought I'd share my experience with them. Here's a pic:

image.jpg

[Bitsyncmaster]

Passive components (motors, light bulbs, etc.) will draw less power when you have bad connections on 12 volts or grounds. The bad connections have resistance which cause voltage drops and less voltage at the load.

Switching regulators will draw more current with bad connections because lower input voltage needs more current to keep the output voltage at normal levels.

[hmcelraft]

Long ago I found that the fused fans plus a circuit breaker combination with a single relay was too hot and too unreliable. This was after the fan fail relay and OEM circuit breaker melted down shortly after I bought my first new DeLorean in Jan of 1982.

Initially I tried it all --- the modification using fuses (melted several times) the 40 amp circuit breaker, etc. In 1983 or 1984 I rewired the fans for a single relay each and a single 15 amp HD circuit breaker for each fan. Finally low heat and measured amperage at the fans about 11-12 amps each. I wired the fans to come on and run continuously while the AC was turned on and work normally when the AC was turned off. I lived in Houston and the AC was on virtually year-round anyway. I replaced the fans once at about 60,000 miles (I could have rebuilt them - just brushes worn out). I sold the car in 1988 with 95,000 miles on the car and they were working great. I had acquired another 5 speed from my dealer in 1984 and had modified the wiring similarly. It had about 40,000 miles on it when it was sold. No issues with fans. The Automatic I have now, acquired in 1987 with 8,000 miles on it, has my modified wiring method applied to it -- plus, I decided to run the power supply wires directly from the battery. Early last year (about 97,000 miles) I replaced the fans with some NOS OEM fans I had because I was changing the radiator and didn't want to mess with fans in the future. The brushes were in fact worn out on one of the fans. My point to this is that the OEM fans work well if you can get sufficient wiring to them - even though their normal amperage draw is bit high.

As far as electrical strain. I haven't really had an issue. Early days I ran the Motorola alternator and had no issues. I had a Motorola on this current car and I switched to the Delco 130 version because I was afraid the Motorola was wearing out and the Delco version gives me some reserve.

[mr_maxime]

Coolant level is good. I haven't checked to see the if the core is bypassed. I wanted to but wasn't exactly sure what do look for.