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Sorry I can't help with locating a new one, but did you verify that it's not the switch causing the trouble rather than the resistor?
I'm guessing one can fail just as easily as the other, so wondered if it might be the switch.
For the resistor I would check LMC truck perhaps. I know we don't carry them and have not actually ever looked for one of this style before.
The resistor looks like it's in good shape. No burn marks or broken connections.
From what I see on the wiring diagrams, 3 terminal resistors are used on non-AC trucks while the AC trucks got a 4 terminal resistor. The link is for 1979 but since it's the same as 1976 and there isn't a diagram for 1977, it'll have to do.
Because it just reduces voltage, it also reduces torque which means that if your blower is on the weak side, it may not run at lower speeds. Mine won't start on low but will run on low if it's been bump started on medium or high and left to warm up a bit.
The blower switch bypasses the resistor on high so that the motor gets full voltage. Verify that you have battery voltage on the black with yellow stripe when the switch is on high. If you do, the motor needs help. Or one of the air flaps is in the wrong position or your cowl is full of squirrels
X2 on what lasermike said. My trucks all came with factory A/C and have the 4 terminal resistor. I recently replaced the blower motor on my Bronco and it wouldn't move on any speed other than high and even then barely and only after I pulled it out and turned the motor by hand to free it, because it was so worn out and would stick badly. My blower motor will turn on without the resistor plugged in, but only on high like lasermike said.
1973/79 F100/350 & 1978/79 Bronco with heater or dealer installed A/C only.
1969/72 Galaxie/LTD/Marquis with heater only.
MCDONALD OBSOLETE PARTS in Rockport IN has 1 = 812-359-4965.
CARPENTER NOS OBSOLETE PARTS in Concord NC has 1 = 800-476-9653.
LINCOLN/MERCURY OLD PARTS STORE in Clearwater FL has 1 = 727-445-7551.
------------------------------------------------------------------------------------------ D3TZ-19706-A .. Blower Motor Resistor / Obsolete
1973/79 F100/350 & 1978/79 Bronco with factory installed integral A/C or Hi/Lo Comfort Vent System.
NOS PARTS LTD in Waxahachie TX has 4 = 972-937-2201.
The resistor looks like it's in good shape. No burn marks or broken connections.
From what I see on the wiring diagrams, 3 terminal resistors are used on non-AC trucks while the AC trucks got a 4 terminal resistor. The link is for 1979 but since it's the same as 1976 and there isn't a diagram for 1977, it'll have to do.
Because it just reduces voltage, it also reduces torque which means that if your blower is on the weak side, it may not run at lower speeds. Mine won't start on low but will run on low if it's been bump started on medium or high and left to warm up a bit.
The blower switch bypasses the resistor on high so that the motor gets full voltage. Verify that you have battery voltage on the black with yellow stripe when the switch is on high. If you do, the motor needs help. Or one of the air flaps is in the wrong position or your cowl is full of squirrels
Michael
I just replaced the blower motor and cage about three months ago and when I hooked it up and tested it it blew really hard now its not. I'll just to see if its getting full 12v.
I dont have low, mid only sort of high. It does not really push the air.
So i just pulled it out. I went to look for one and everything I see as 4 prong
and mine has 3.
Can someone tell me where to find one or will the 4 work and just change the plug out?
77 f250 4x4 economy a/c
hoping you still have the rig. I recently bought a 77 f250 with economy ac but some pack rats got to the wiring first. Could you tell me where the red capped blade connector that comes out of the back of the ac control switch box runs to. The factory ac uses the 4th blower resistor blade connector but the economy doesn't have that. I cant seem to find a wire that it would have gone to that is just floating around. The diagram calls for a safty relay but I dont see one.
I ordered one from Macks 4 months ago,,still on backorder.
I got a new old stock from Ebay said it was in an estate of a former ford engineer. Said it was used in the factory as a testing device. Probably all crap but it was the cheepest one and came in
copied the listing description
1973 1974 1975 1976 1977 1978 1979 FORD F150 F250 F350 1978 1979 1980 1981 1982 1983 1984 1985 1986 BRONCO HEATER BLOWER MOTOR RESISTOR.
This OEM FOMOCO resister was found at the estate of a Ford engineer. It looks to be in excellent condition unused but has some witness marks on the terminals. It is very clean. I don’t believe this is a service part but an original assembly line part that was probably used for testing.
When I ordered threw Mac's it said in stock ,,,,after purchase a day or so later ,got a note said backordered
I completely understand. Currently I'm in desperate search for a float for a 4350 motorcraft 77-79 and every new old stock site says they have it but call or email first and have them send a picture. Usually if they cant provide a picture in 3 days it's a fake site or they just don't have it. So far they have all be honest and told me it's a empty box on the shelf or they plain don't have it. I did have one rude representative from https://www.carburetion.com that told me it was funny I couldn't find it. He also after I told him sites like his that list things in stock and dont actually have stock flood the market and make it more difficult to find. He just typed in all caps to read the posting that they have limited supply. Then responded lol after I told him limited means at least one. So in the future call in first and send emails before purchasing. Sorry for the long rant but if it helps you get the part you need quicker than it was worth it. Get them to send you a picture too.
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