1989 f150 starter wont stop cranking even with ignition off

[jjk_52]

Ok I really need some help here. This is my first truck and i love it. but i went to start it to go to work to day and it started fine but the starter wouldnt turn off. i turned the ignition off and it kept going, so i disconnected the battery. But as soon as i connect it again the starter starts going again. Im so confused I really hope you guys can help me here!

[Selectron]

Could be a faulty starter relay, could be a fault in the wiring, or it could be a faulty starter motor assembly (specifically, the starter solenoid, which is physically attached to the starter motor body).

I would recommend that you do what I suggested to another F150 owner in this post - he had the same problem. What you would be doing is disabling the regular starter circuit and adding a manual starting wire.

That will quickly tell you if the fault is in the starter assembly or elsewhere. If the fault is in the starter then you have no option but to have it repaired or replaced, but if the fault is elsewhere then having the manual starting wire will enable you to keep the truck in use, and fix the fault later when you have some free time.

If you find you need to do some electrical fault-finding then all the information in post #6 on this thread will be applicable to your vehicle, with the possible exception that the thin wire which connects to the small terminal on the starter motor assembly might be a different colour.

[jjk_52]

Ok i will try a new relay. the guy thaqt had the truck before me installed a push button starter on the truck because it sometimes wouldnt start. im going to try that today and if it dont work ill be back on here

[Selectron]

Push button starter eh; that raises a couple of issues. Firstly, the relay might no longer be in-circuit - he might have fed 12 volts to the switch and then straight on down to the starter solenoid, bypassing the relay altogether - might have or might not - you'd need to follow the wiring to verify that. Easiest way is to go to the starter motor and follow the thin wire backwards and see if it comes from the starter relay or direct from the dashboard switch.

Second issue is that if it's an amateur installation then it might have failed due to poor wiring - I'd probably remove the switch and see if there are any uninsulated wires or connectors at the back which have become crossed, and are shorting out against each other.

I'd take a guess that the starter motor assembly will prove to be good, and the fault will be in the wiring. If that's the case then you can quickly put the truck back into use by temporarily fitting your own manual start wire and sort the wiring out later, especially if you need it to travel to work.

[jjk_52]

I replaced the relay/sliinoid and it fired up right away no problems. thanks so much the part only cost like 30 buck so i was pretty happy bout that. and i went through and checked all the wiring for the push button and it all seems good looks like he knew what he was doing. thanks a lot.

[jjk_52]

oh wait would you happen to have ant idea why my heater fan wont work?

[Selectron]

That's good that you got the starter fixed. If the heater blower motor isn't working on any of the speed settings then the fault could be almost anything - to pinpoint the fault you would need to do some voltage checks using either a multimeter (DC voltage range) or a 12 volt test lamp.

Unfortunately, the Autozone website doesn't have a wiring diagram available, but Ford always use pretty much the same arrangement - 12 volts is fed to the blower motor positive terminal, and then the negative terminal feeds into a resistor pack (for selecting the different speed settings), then into the speed selector switch, and then to ground.

The easiest way to approach it is to find the blower motor connector, switch the ignition on and set the speed selector switch to Hi-Speed, and then check for 12 volts at the blower motor's positive terminal. If you don't have 12 volts then the problem is prior to that point, but if you do have 12 volts then the problem is after that point, so it's a quick way to divide the circuit in two and find out which side has the fault. This is how to proceed depending on the voltages at the motor:

If you don't have 12 volts at the positive terminal then check all fuses - there will likely be two in the circuit - one to feed the blower motor relay's coil, and another to feed its switched contacts. Just to complicate matters, Ford didn't always use a relay, in which case the motor would be fed from a circuit breaker instead. So the problem would be either a fuse, relay, circuit breaker, or the associated wiring.

If on the other hand you find you do have 12 volts at the motor positive terminal, then check to see if you also have 12 volts on its negative terminal - if you do then that indicates an open-circuit in the negative side of the circuit, between that point and ground. That could be a faulty resistor pack, faulty speed selector switch, faulty connector or wiring, or a bad ground connection.

The motor itself can also fail, but you can apply 12 volts and a ground directly to the motor to determine whether or not it's faulty.

It's an easy enough circuit to work on, especially if you have a wiring diagram available, but access on most vehicles tends to be cramped and awkward.