I have a 1991 with an Isuzu 4bd1t. I'm using a new sanden 708 series compressor. I've replaced all o-rings in entire system, expansion valve, accumulator/dryer, removed and cleaned evaporator core. The ac blew ice cold with no issues before I did this swap. Also it was retrofitted with r134 before the swap also. I took it to an ac repair shop and they put it on a machine, pulled a vacuum and it was determined to be a solid system with no leaks. I added 7oz of pag 46 oil to system after draining the oil that new compressor came shipped with btw. They charged the system according to the manual and by converting factory r12 charge to r134 required amount. Here's where my problem lies, compressor kicks in as it should when system is first turned on and then after a min or two the compressor begins cycling on/off very rapidly. The shop believes the pressure switch may be bad but I don't believe that it is. Everything worked as it should before the swap. I've read where a 62 series ac amp can fix this but only seen it in a 60 series not an 80. Anyone with an 80 used a 62 amp? Does the 80 require a coil signal to start the ac amp? Currently I have the stock coil wire not connected to anything. I really need some help here as this is my daily driver and I have a 2 year old and this Tennessee heat is too much for him in my rig!
Need ac help on 4bd1t swap (1 Viewer)
- Thread starter TNNPIG
- Start date
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Paging @ThreeEyedBandit
He's running a 4bd1t I believe, but don't recall if his A/C is functioning or not. Think he is on a roadtrip today, but maybe he will chime in.
He's running a 4bd1t I believe, but don't recall if his A/C is functioning or not. Think he is on a roadtrip today, but maybe he will chime in.
Have you checked the AC pressures? If the system is over/under charged the compressor could cycle on/off as the pressure hits the upper/lower limit. Can you check the electrical resistance of the new compressor clutch? The stock Toyota clutch should be 3.8Ohm (for an 94 but the compressors are identical). If the Sanden clutch has a different resistance that could be causing problems. It would be a little odd for the amplifier/relay/trinary switch to work pre-swap then immediately fail post-swap.
I still need to convince ole @ThreeEyedBandit to carve me an adaptor for my 4bd2t swap.
It sounds like it might be overcharged. Did the shop note what the pressures were when it cycled off? FWIW, Sanden 508/708 compressors typically use PAG 100, although that won't cause the issue you're facing. If you don't have access to a set of gauges, use a garden hose to soak the condenser when the compressor starts cycling off. If it stops cycling and stays on, it's a good bet it's overcharged.
